TSPO ligands

Cross-reference to related application(s)

[0001] The present application claims priority from Australian Provisional Patent Application 2022903474 filed on 18 November 2022, the entire contents of which is incorporated herein by reference.

Field of the invention

[0002] The present disclosure relates to compounds that bind translocator protein (18 kDa) (TSPO), and methods for their use.

Background of the invention

[0003] Translocator protein (18 kDa) (TSPO), also called the peripheral benzodiazepine receptor (PBR), is a highly conserved mitochondrial protein predominantly expressed in the outer mitochondrial membrane in steroid-synthesising tissues. TSPO forms part of a large transmembrane complex that facilitates cholesterol translocation across the mitochondrial membrane. TSPO has been implicated in other cellular processes, although the full scope of its functions remains unclear.

[0004] Brain TSPO expression is relatively low under physiological conditions, but is upregulated in response to glial cell activation. TSPO is a validated biomarker for neuroinflammation and is implicated in the pathogenesis and progression of central nervous system (CNS) and neurodegenerative disorders, including Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease, multiple sclerosis, major depressive disorde and obsessive compulsive disorder. Imaging TSPO using Positron Emission Tomography (PET) has been one of the most widely used techniques for assessing and quantifying neuroinflammation.

[0005] Numerous TSPO-targeted PET tracers have been developed for imaging TSPO. One example is first generation TSPO tracer [ ¹¹ C]PK-1 1 195. [ ¹¹ C]PK-1 1 195 is widely used as a pharmacological probe for studying the function and expression of TSPO. However, it exhibits high levels of non-specific binding and has demonstrated low brain permeability, giving poor signal-to-noise ratios and low-quality images.

Second generation TSPO tracers such as [ ¹¹ C]DPA-713 and [ ¹⁸ F]DPA-714 have higher specificity for TSPO. However, these and other second generation compounds have been found to exhibit different affinities for TSPO in different patients, with this differential affinity relating to patient genotype. In particular, these radioligands were found to bind differently to two commonly found isoforms of the TSPO protein: the wildtype (WT, more common) and the A147T variant (less common). Poor binding to the latter TSPO isoform means that these ligands cannot be used for PET imaging for all patients, since up to 30% of humans express the mutated version of TSPO, depending on ethnicity.

[0006] It would therefore be advantageous to provide compounds capable of binding to TSPO with high specificity and high affinity. It would also be advantageous to provide these compounds that are not sensitive to patient TSPO genotype.

[0007] All publications, patents and patent applications that may be cited herein are hereby incorporated by reference in their entirety.

[0008] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

Summary

[0009] In one aspect there is provided a compound of formula (I): wherein: i) R ¹ is selected from optionally substituted Ci ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca- cycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted Ci- ealkylaryl, optionally substituted Ci-ealkyl-Cs- cycloalkyl, optionally substituted Ci-ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl, and

R ² is selected from hydrogen, optionally substituted Ci ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci- ealkoxyhalo; or ii) R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl; and

R ³ is selected from hydrogen, halo, optionally substituted Ci ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci- ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted Ci-4alkyl, or

R ^a and R ^b together form =0; and with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted C3-9cycloalkyl, optionally substituted heteroaryl, optionally substituted Cs-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci-ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl, and when R ¹ is phenyl and R ² is ethyl, R ³ is not Ci -ealkoxyhalo, optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof. [0010] The inventors have found that the compounds of formula (I) selectively bind to TSPO with high affinity. The inventors have also found that the compounds of formula (I) bind with high affinity to both wild-type TSPO and A147T mutant TSPO.

[0011] In some embodiments, the compound of the invention is radiolabelled at R ³ .

[0012] In some embodiments, the compound of the invention is selected from any one of compounds 1 -23. In some embodiments, the compound of the invention is selected from any one of compounds 1 -13.

[0013] In another aspect, there is provided a medicament comprising a compound of the invention.

[0014] In another aspect, there is provided a diagnostic agent comprising a compound of the invention.

[0015] In another aspect, there is provided a pharmaceutical composition comprising a compound of the invention and a pharmaceutically acceptable excipient.

[0016] In another aspect, there is provided a diagnostic composition comprising a compound of the invention and a pharmaceutically acceptable excipient.

[0017] In another aspect, there is provided use of a compound of the invention for detecting elevated levels of TSPO expression by detecting a signal from the compound. The TSPO expression is correlated with the signal from the compound.

[0018] In another aspect, there is provided a method for determining the distribution and/or extent of TSPO expression in a subject, the method comprising: administering a compound of the invention, which is radiolabelled, to the subject; and detecting a signal from the compound in the subject.

[0019] In another aspect, there is provided a method for diagnosing a CNS disorder and/or a neurodegenerative disorder in a subject, the method comprising: administering a compound of the invention, which is radiolabelled, to the subject; and detecting a signal from the compound in the subject.

[0020] In another aspect, there is provided a method for treating a disease, condition and/or disorder associated with modulation of TSPO in a subject, the method comprising: administering a of the invention, which is radiolabelled, to the subject; detecting a signal from the compound in the subject; and administering a compound of the invention, which is optionally radiolabelled, to the subject.

[0021] In another aspect, there is provided a method for treating a disease, condition and/or disorder associated with modulation of TSPO, the method comprising administering to a subject in need thereof a compound of the invention, which is optionally radiolabelled.

[0022] In another aspect, there is provided a method for treating a CNS disorder and/or a neurodegenerative disorder, the method comprising: administering a compound of the invention, which is radiolabelled, to the subject; detecting a signal from the compound in the subject; and administering a compound of the invention, which is optionally radiolabelled, to the subject.

[0023] In another aspect, there is provided a method for treating a CNS disorder and/or a neurodegenerative disorder, the method comprising administering to a subject in need thereof a compound of the invention, which is optionally radiolabelled.

[0024] In some embodiments, the subject expresses wild-type TSPO and A147T mutant TSPO.

[0025] In another aspect, there is provided a compound of formula (Ila): wherein: i) R ¹ is selected from optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca-iocycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci -ealkyl-Cs-iocycloalkyl, optionally substituted Ci -ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl, and

R ² is selected from hydrogen, optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted C1- ealkoxyhalo; or ii) R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl; and

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ¹ is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted C3- cycloalkyl, optionally substituted heteroaryl, optionally substituted C3- ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci ealkyl- Cs-iocycloalkyl, optionally substituted Ci -ealkyl heteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0026] In some embodiments, J ¹ is an optionally substituted optionally substituted Ci- ealkoxy, preferably a methoxy group.

[0027] In another aspect, there is provided a compound of formula (lib): wherein:

R ² is selected from hydrogen, optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo;

R ³ is selected from hydrogen, halo, optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted C1- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ² is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, J ² is selected from hydrogen, optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted Ca-gcycloalkyl, optionally substituted heteroaryl, optionally substituted C3- ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci ealkyl- Cs-iocycloalkyl, optionally substituted Ci -ealkyl heteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0028] In another aspect, there is provided a compound of formula (He): wherein:

R ¹ is selected from optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl or optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted C3- locycloalkyl, optionally substituted heteroaryl, optionally substituted C3- ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci ealkyl- C3-iocycloalkyl, optionally substituted Ci -ealkyl heteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl,

R ³ is selected from hydrogen, halo, optionally substituted Ci ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted C1- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ³ is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted C3- gcycloalkyl, optionally substituted heteroaryl, optionally substituted Cs-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci -ealkylheteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0029] In another aspect, there is provided a compound of formula (lid): wherein:

A is an optionally substituted heterocyclyl or optionally substituted heteroaryl; wherein A includes J ⁴ as part of the heterocyclic or heteroaryl ring or a substituent on the heterocyclic or heteroaryl ring;

R ³ is selected from hydrogen, halo, optionally substituted C-i-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci- ealkylhalo, optionally substituted Ci ealkoxy and optionally substituted Ci ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted Ci- 4alkyl, or

R ^a and R ^b together form =0; and

J ⁴ is a moiety that is capable of modification to introduce a radionuclide into the compound; or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0030] In another aspect, there is also provided a process for preparing a compound of formula (I), which is optionally radiolabelled, or a salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0031] In some embodiments, the compound of formula (I), which is radiolabelled at R ³ , is prepared from a compound of formula (Ila). [0032] In some embodiments, the compound of formula (I), which is radiolabelled at R ¹ , is prepared from a compound of formula (lib).

[0033] In some embodiments, the compound of formula (I), which is radiolabelled at R ² , is prepared from a compound of formula (He).

[0034] In some embodiments, the compound of formula (I), which is radiolabelled as part of the heterocyclic or heteroaryl ring or a substituent on the heterocyclic or heteroaryl ring at A, is prepared from a compound of formula (lid).

[0035] Any embodiment herein shall be taken to apply mutatis mutandis to any other embodiment unless specifically stated otherwise.

[0036] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the invention, as described herein.

[0037] Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or group of compositions of matter.

[0038] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example.

Detailed description of the embodiments

[0039] Current second generation PET tracers used for imaging TSPO to assess neuroinflammation suffer from poor sensitivity and/or only function in about 30% of patients (up to about 70% in subpopulations) due to a common TSPO variant in the human genome. In order to use these second generation TSPO PET tracers, patients must first be genotyped to determine whether or not they have the rs6971 singlenucleotide polymorphism that results in the expression of A147T TSPO. Patients expressing this variant may express both wild type and A147T TSPO or exclusively A147T TSPO, and make up about 30% of the patient population. Current TSPO PET tracers do not bind with suitable affinity to A147T to give a sufficiently strong PET signal. Therefore, such PET tracers exhibit lower sensitivity with patients who express both wild type and A147T TSPO, and cannot be used for patients who exclusively express A147T TSPO. This immediately excludes up to about 30% of the population from experiencing the benefits of these imaging tools.

[0040] The inventors have shown that compounds of formula (I) bind TSPO with high selectivity and high affinity for both wild-type and A147T mutant isoforms of TSPO. Accordingly, the compounds of formula (I) can be used as PET tracers for TSPO in patients expressing either or both of wild type and A147T mutant TSPO. This advantageously allows the compounds to be useful for a broader population. This also advantageously allows the compounds to be used without the need for prior genotyping of patients, saving time, money and resources - and thus providing a benefit for all subjects regardless of whether they express the wild type TSPO or the A147T mutant TSPO.

Definitions

[0041] Unless otherwise herein defined, the following terms will be understood to have the general meanings which follow.

[0042] The term “Ci -ealkyl” refers to optionally substituted straight chain or branched chain hydrocarbon groups having from 1 to 6 carbon atoms. Examples include methyl (Me), ethyl (Et), propyl (Pr), isopropyl (i-Pr), butyl (Bu), isobutyl (i-Bu), sec-butyl (s-Bu), tert-butyl (t-Bu), pentyl, neopentyl, hexyl and the like. Unless the context requires otherwise, the term “Ci -ealkyl” also encompasses alkyl groups containing one less hydrogen atom such that the group is attached via two positions i.e. divalent. “Ci-4alkyl” and “Ci-ealkyl” including methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, sec-butyl and tert-butyl are preferred with methyl and ethyl being particularly preferred and with methyl being more particularly preferred.

[0043] The term “C2-6alkenyl” refers to optionally substituted straight chain or branched chain hydrocarbon groups having at least one double bond of either Eor Z stereochemistry where applicable and 2 to 6 carbon atoms. Examples include vinyl, 1 - propenyl, 1 - and 2-butenyl and 2-methyl-2-propenyl. Unless the context requires otherwise, the term “C2-6alkenyl” also encompasses alkenyl groups containing one less hydrogen atom such that the group is attached via two positions i.e. divalent. “C2- 4alkenyl” and “C2-3alkenyl” including ethenyl, propenyl and butenyl are preferred with ethenyl being particularly preferred.

[0044] The term “C2-6alkynyl” refers to optionally substituted straight chain or branched chain hydrocarbon groups having at least one triple bond and 2 to 6 carbon atoms. Examples include ethynyl, 1 -propynyl, 1 - and 2-butynyl, 2-methyl-2-propynyl, 2- pentynyl, 3-pentynyl, 4-pentynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl and 5-hexynyl and the like. Unless the context indicates otherwise, the term “C2-6alkynyl” also encompasses alkynyl groups containing one less hydrogen atom such that the group is attached via two positions i.e. divalent. C2-3alkynyl is preferred.

[0045] The term “Cs-iocycloalkyl” refers to non-aromatic cyclic groups having from 3 to 10 carbon atoms, including cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl and cyclodecyl. It will be understood that cycloalkyl groups may be saturated such as cyclohexyl or unsaturated such as cyclohexenyl. C3- scycloalkyl such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl are preferred and Cs ecycloalkyl such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl are particularly preferred. Cycloalkyl groups also include polycyclic carbocycles and include fused, bridged and spirocyclic systems. Examples of cycloalkyl groups include adamantyl, cubanyl, spiro[3.3]heptanyl, bicyclo(1 .1 .1)pentanyl, bicycle(2.2.1 )heptanyl, and bicyclo(2.2.2)octanyl groups.

[0046] The terms “hydroxy” and “hydroxyl” refer to the group -OH.

[0047] The term “oxo” refers to the group =0.

[0048] The term “Ci -ealkoxy” refers to an alkyl group as defined above covalently bound via an O linkage containing 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isoproxy, butoxy, tert-butoxy and pentoxy. “Ci-4alkoxy” and “Ci-3alkoxy” including methoxy, ethoxy, propoxy and butoxy are preferred with methoxy being particularly preferred.

[0049] The terms “Ci-ealkylhalo” and “haloCi-ealkyl” refer to a Ci -ealkyl which is substituted with one or more halogens. Ci shaloalkyl groups are preferred, such as for example, -CH2F, -CH2CH2F and -CH2CH2CH2F. [0050] The terms “Ci -ealkoxyhalo” and “haloCi -ealkoxy” refer to a Ci -ealkoxy which is substituted with one or more halogens. Ci -ealkoxyhalo groups are preferred, such as for example, -OCH2F, -OCH2CH2F and -OCH2CH2CH2F.

[0051] The term “aralkyl” refers to an aryl group having a hydrogen replaced with an alkyl group. Benzyl groups are preferred.

[0052] The term “carboxylate” or “carboxyl” refers to the group -COO- or -COOH.

[0053] The term “ester” refers to a carboxyl group having the hydrogen replaced with, for example, a Ci -ealkyl group (“carboxylCi -ealkyl” or “alkylester”), an aryl or aralkyl group (“arylester” or “aralkylester”) and so on. CO2C1 -ealkyl groups are preferred, such as for example, methylester (CO2Me), ethylester (CO2Et) and propylester (CO2Pr) and includes reverse esters thereof (e.g. -OC(O)Me, -OC(O)Et and -OC(O)Pr).

[0054] The terms “cyano” and “nitrile” refer to the group -CN.

[0055] The term “nitro” refers to the group -NO2.

[0056] The term “amino” refers to the group -NH2.

[0057] The term “substituted amino” refers to an amino group having at least one hydrogen replaced with, for example a Ci -ealkyl group (“Ci-ealkylamino”), an aryl or aralkyl group (“arylamino”, “aralkylamino”) and so on. Substituted amino groups include “monosubstituted amino” (or “secondary amino”) groups, which refer to an amino group having a single hydrogen replaced with, for example a C-i ealkyl group, an aryl or aralkyl group and so on. Preferred secondary amino groups include Ci-ealkylamino groups, such as for example, methylamino (NHMe), ethylamino (NHEt) and propylamino (NHPr). Substituted amino groups also include “disubstituted amino” (or “tertiary amino”) groups, which refer to amino groups having both hydrogens independently replaced with, for example Ci ealkyl groups, which may be the same or different (“dialkylamino”), aryl and alkyl groups (“aryl(alkyl)amino”) and so on. Preferred tertiary amino groups include di(Ci-3alkyl)amino groups, such as for example, dimethylamino (NMe2), diethylamino (NEtz), dipropylamino (NPr2) and variations thereof (e.g. N(Me)(Et) and so on).

[0058] The term “aldehyde” refers to the group -C(=O)H. [0059] The terms “acyl” and “acetyl” refers to the group -C(O)CH3.

[0060] The term “ketone” refers to a carbonyl group which may be represented by - C(O)-.

[0061] The term “substituted ketone” refers to a ketone group covalently linked to at least one further group, for example, a Ci -ealkyl group (“Ci -ealkylacyl” or “alkylketone” or “ketoalkyl”), an aryl group (“arylketone”), an aralkyl group (“aralkylketone) and so on. Ci- aalkylacyl groups are preferred.

[0062] The term “amido” or “amide” refers to the group -C(O)NH2.

[0063] The term “substituted amido” or “substituted amide” refers to an amido group having a hydrogen replaced with, for example a Ci -ealkyl group (“Ci-ealkylamido” or “Ci-ealkylamide”), an aryl (“arylamido”), aralkyl group (“aralkylamido”) and so on. Ci-3alkylamide groups are preferred, such as for example, methylamide (-C(O)NHMe), ethylamide (-C(O)NHEt) and propylamide (-C(O)NHPr) and includes reverse amides thereof (e.g. -NHMeC(O)-, -NHEtC(O)- and -NHPrC(O)-).

[0064] The term “disubstituted amido” or “disubstituted amide” refers to an amido group having the two hydrogens independently replaced with, for example a Ci ealkyl group (“di(Ci-6alkyl)amido” or “di(Ci-6alkyl)amide”), an aralkyl and alkyl group (“alkyl(aralkyl)amido”) and so on. Di(Ci-3alkyl)amide groups are preferred, such as for example, dimethylamide (-C(O)NMe2), diethylamide (-C(O)NEt2) and dipropylamide ((- C(O)NPr2) and variations thereof (e.g. -C(O)N(Me)Et and so on) and includes reverse amides thereof.

[0065] The term “thiol” refers to the group -SH.

[0066] The term “Ci -ealkylthio” refers to a thiol group having the hydrogen replaced with a Ci-ealkyl group. C-i-salkylthio groups are preferred, such as for example, thiolmethyl, thiolethyl and thiolpropyl.

[0067] The terms “thioxo” refer to the group =S.

[0068] The term “sulfinyl” refers to the group -S(=O)H. [0069] The term “substituted sulfinyl” or “sulfoxide” refers to a sulfinyl group having the hydrogen replaced with, for example a Ci ealkyl group (“Ci -ealkylsulfinyl” or “Ci-ealkylsulfoxide”), an aryl (“arylsulfinyl”), an aralkyl (“aralkyl sulfinyl”) and so on. C1 -3alkylsulfinyl groups are preferred, such as for example, -SOmethyl, -SOethyl and - SOpropyl.

[0070] The term “sulfonyl” refers to the group -SO2H.

[0071] The term “substituted sulfonyl” refers to a sulfonyl group having the hydrogen replaced with, for example a Ci -ealkyl group (“sulfonylCi-ealkyl”), an aryl (“arylsulfonyl”), an aralkyl (“aralkylsulfonyl”) and so on. SulfonylCi -ealkyl groups are preferred, such as for example, -SC Me, -SC Et and -SC Pr.

[0072] The term “sulfonylamido” or “sulfonamide” refers to the group -SO2NH2.

[0073] The term “substituted sulfonamido” or “substituted sulphonamide” refers to a sulfonylamido group having a hydrogen replaced with, for example a Ci ealkyl group (“sulfonylamidoCi-ealkyl”), an aryl (“arylsulfonamide”), aralkyl (“aralkylsulfonamide”) and so on. SulfonylamidoCi-ealkyl groups are preferred, such as for example, -SC NHMe, -SC NHEt and -SC NHPr and includes reverse sulfonamides thereof (e.g. -NHSO ₂ Me, -NHSO ₂ Et and -NHSO ₂ Pr).

[0074] The term “disubstituted sufonamido” or “disubstituted sulphonamide” refers to an sulfonylamido group having the two hydrogens independently replaced with, for example a Ci -ealkyl group, which may be the same or different (“sulfonylamidodi(Ci- ealkyl)”), an aralkyl and alkyl group (“sulfonamido(aralkyl)alkyl”) and so on. Sulfonylamidodi(Ci-3alkyl) groups are preferred, such as for example, -SO2NMe2, - SO2NEt2 and -SO2NPr2 and variations thereof (e.g. -SO2N(Me)Et and so on) and includes reserve sulfonamides thereof (e.g. -N(Me)SO2Me and so on).

[0075] The term “sulfate” refers to the group OS(O)2OH and includes groups having the hydrogen replaced with, for example a Ci ealkyl group (“alkylsulfates”), an aryl (“arylsulfate”), an aralkyl (“aralkylsulfate”) and so on. Ci-3sulfates are preferred, such as for example, OS(O)2OMe, OS(O)2OEt and OS(O)2OPr.

[0076] The term “sulfonate” refers to the group SO3H and includes groups having the hydrogen replaced with, for example a Ci -ealkyl group (“alkylsulfonate”), an aryl (“arylsulfonate”), an aralkyl (“aralkylsulfonate”) and so on. Ci-3sulfonates are preferred, such as for example, SOaMe, SOaEt and SOaPr.

[0077] The term “aryl” refers to a carbocyclic (non-heterocyclic) aromatic ring or mono-, bi- or tri-cyclic ring system. Polycyclic ring systems may be referred to as “aryl” provided at least 1 of the rings within the system is aromatic. The aromatic ring or ring system is generally composed of 6 to 10 carbon atoms. Examples of aryl groups include but are not limited to phenyl, biphenyl, naphthyl and tetrahydronaphthyl. 6-membered aryls such as phenyl are preferred. The term “alkylaryl” refers to Ci ealkylaryl such as benzyl.

[0078] The term “alkoxyaryl” refers to Ci -ealkyl oxyaryl such as benzyloxy.

[0079] The term “heterocyclyl” refers to a moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound which moiety has from 3 to 10 ring atoms (unless otherwise specified), of which 1 , 2, 3 or 4 are ring heteroatoms each heteroatoms being independently selected from O, S and N. Heterocyclyl groups include monocyclic and polycyclic (such as bicyclic) ring systems, such as fused, bridged and spirocyclic systems, provided at least one of the rings of the ring system contains at least one heteroatom.

[0080] In this context, the prefixs 3-, 4-, 5-, 6-, 7-, 8-, 9- and 10- membered denote the number of ring atoms, or range of ring atoms, whether carbon atoms or heteroatoms. For example, the term “3-10 membered heterocylyl”, as used herein, pertains to a heterocyclyl group having 3, 4, 5, 6, 7, 8, 9 or 10 ring atoms. Examples of heterocylyl groups include 5-6-membered monocyclic heterocyclyls and 9-10 membered fused bicyclic heterocyclyls.

[0081] Heterocyclyls encompass aromatic heterocyclyls and non-aromatic heterocyclyls. Such groups may be substituted or unsubstituted.

[0082] The term “aromatic heterocyclyl” may be used interchangeably with the term “heteroaromatic” or the term “heteroaryl” or “hetaryl”. The heteroatoms in the aromatic heterocyclyl group may be independently selected from N, S and O. The aromatic heterocyclyl groups may comprise 1 , 2, 3, 4 or more ring heteroatoms. In the case of fused aromatic heterocyclyl groups, only one of the rings may contain a heteroatom and not all rings must be aromatic. [0083] “Heteroaryl” is used herein to denote a heterocyclic group having aromatic character and embraces aromatic monocyclic ring systems and polycyclic (e.g. bicyclic) ring systems containing one or more aromatic rings. The term aromatic heterocyclyl also encompasses pseudoaromatic heterocyclyls. The term “pseudoaromatic” refers to a ring system which is not strictly aromatic, but which is stabilized by means of delocalization of electrons and behaves in a similar manner to aromatic rings. The term aromatic heterocyclyl or heteroaryl therefore covers polycyclic ring systems in which all of the fused rings are aromatic as well as ring systems where one or more rings are non-aromatic, provided that at least one ring is aromatic. In polycyclic systems containing both aromatic and non-aromatic rings fused together, the group may be attached to another moiety by the aromatic ring or by a non-aromatic ring.

[0084] Examples of heteroaryl groups are monocyclic and bicyclic groups containing from five to ten ring members. The heteroaryl group can be, for example, a five membered or six membered monocyclic ring or a bicyclic structure formed from fused five and six membered rings or two fused six membered rings or two fused five membered rings. Each ring may contain up to about four heteroatoms typically selected from nitrogen, sulphur and oxygen. The heteroaryl ring will contain up to 4 heteroatoms, more typically up to 3 heteroatoms, more usually up to 2, for example a single heteroatom. In one embodiment, the heteroaryl ring contains at least one ring nitrogen atom. The nitrogen atoms in the heteroaryl rings can be basic, as in the case of an imidazole or pyridine, or essentially non-basic as in the case of an indole or pyrrole nitrogen. In general the number of basic nitrogen atoms present in the heteroaryl group, including any amino group substituents of the ring, will be less than five.

[0085] Aromatic heterocyclyl or heteroaryl groups may be 5-membered or 6- membered mono-cyclic aromatic ring systems.

[0086] Examples of 5-membered monocyclic heteroaryl groups include but are not limited to furanyl, thienyl, pyrrolyl, oxazolyl, oxadiazolyl (including 1 ,2,3 and 1 ,2,4 oxadiazolyls and furazanyl i.e. 1 ,2,5-oxadiazolyl), thiazolyl, isoxazolyl, isothiazolyl, pyrazolyl, imidazolyl, triazolyl (including 1 ,2,3, 1 ,2,4 and 1 ,3,4 triazolyls), oxatriazolyl, tetrazolyl, thiadiazolyl (including 1 ,2,3 and 1 ,3,4 thiadiazolyls) and the like.

[0087] Examples of 6-membered monocyclic heteroaryl groups include but are not limited to pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl, pyranyl, oxazinyl, dioxinyl, thiazinyl, thiadiazinyl and the like. Examples of 6-membered aromatic heterocyclyls containing nitrogen include pyridyl (1 nitrogen), pyrazinyl, pyrimidinyl and pyridazinyl (2 nitrogens).

[0088] Aromatic heterocyclyl or heteroaryl groups may also be bicyclic or polycyclic heteroaromatic ring systems such as fused ring systems (including purine, pteridinyl, napthyridinyl, 1 H thieno[2,3-c]pyrazolyl, thieno[2,3-b]furyl and the like) or linked ring systems (such as oligothiophene, polypyrrole and the like). Fused ring systems may also include aromatic 5-membered or 6-membered heterocyclyls fused to carbocyclic aromatic rings such as phenyl, naphtyl, indenyl, azulenyl, fluorenyl, anthracenyl and the like, such as 5-membered aromatic heterocyclyls containing nitrogen fused to phenyl rings, 5-membered aromatic heterocyclyls containing 1 or 2 nitrogens fused to phenyl ring.

[0089] A bicyclic heteroaryl group may be, for example, a group selected from: a) a benzene ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms; b) a pyridine ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms; c) a pyrimidine ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; d) a pyrrole ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms; e) a pyrazole ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; f) an imidazole ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; g) an oxazole ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; h) an isoxazole ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; i) a thiazole ring fused to a 5- or 6-membered ring containing 1 or 2 ring heteroatoms; j) an isothiazole ring fused to a 5- or 6-membered ring containing 1 or

2 ring heteroatoms; k) a thiophene ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms; I) a furan ring fused to a 5- or 6-membered ring containing 1 , 2 or

3 ring heteroatoms; m) a cyclohexyl ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms; and n) a cyclopentyl ring fused to a 5- or 6-membered ring containing 1 , 2 or 3 ring heteroatoms.

[0090] Particular examples of bicyclic heteroaryl groups containing a five membered ring fused to another five membered ring include but are not limited to imidazothiazole (e.g. imidazo[2,1 -b]thiazole) and imidazoimidazole (e.g. imidazo[1 ,2-a]imidazole). [0091] Particular examples of bicyclic heteroaryl groups containing a six membered ring fused to a five membered ring include but are not limited to benzofuran, benzothiophene, benzimidazole, benzoxazole, isobenzoxazole, benzisoxazole, benzothiazole, benzisothiazole, isobenzofuran, indole, isoindole, indolizine, indoline, isoindoline, purine (e.g., adenine, guanine), indazole, pyrazolopyrimidine (e.g. pyrazolo[1 ,5-a]pyrimidine), benzodioxole and pyrazolopyridine (e.g. pyrazolo[1 ,5- a] pyridine) groups. A further example of a six membered ring fused to a five membered ring is a pyrrolopyridine group such as a pyrrolo[2,3-b]pyridine group.

[0092] Particular examples of bicyclic heteroaryl groups containing two fused six membered rings include but are not limited to quinoline, isoquinoline, chroman, thiochroman, chromene, isochromene, isochroman, benzodioxan, quinolizine, benzoxazine, benzodiazine, pyridopyridine, quinoxaline, quinazoline, cinnoline, phthalazine, naphthyridine and pteridine groups.

[0093] Examples of heteroaryl groups containing an aromatic ring and a non-aromatic ring include tetrahydronaphthalene, tetrahydroisoquinoline, tetrahydroquinoline, dihydrobenzothiophene, dihydrobenzofuran, 2,3-dihydro- benzo[1 ,4]dioxine, benzo[1 ,3]dioxole, 4,5,6,7-tetrahydrobenzofuran, indoiine, isoindoline and indane groups.

[0094] Examples of aromatic heterocyclyls fused to carbocyclic aromatic rings may therefore include but are not limited to benzothiophenyl, indolyl, isoindolyl, benzofuranyl, isobenzofuranyl, benzimidazolyl, indazolyl, benzoxazolyl, benzisoxazolyl, isobenzoxazoyl, benzothiazolyl, benzisothiazolyl, quinolinyl, isoquinolinyl, quinoxalinyl, quinazolinyl, cinnolinyl, benzotriazinyl, phthalazinyl, carbolinyl and the like.

[0095] The term “non-aromatic heterocyclyl” may be used interchangeably with “heterocycloalkyl” and encompasses optionally substituted saturated and unsaturated rings which contain at least one heteroatom selected from the group consisting of N, S and O. The ring may contain 1 , 2 or 3 heteroatoms. The ring may be a monocyclic ring or part of a polycyclic ring system. Polycyclic ring systems include fused rings and spirocycles. Not every ring in a non-aromatic heterocyclic polycyclic ring system must contain a heteroatom, provided at least one ring contains one or more heteroatoms.

[0096] Non-aromatic heterocyclyls may be 3-7 membered monocyclic rings. [0097] Examples of 5-membered non-aromatic heterocyclyl or heterocycloalkyl rings include 2H-pyrrolyl, 1 -pyrrolinyl, 2-pyrrolinyl, 3-pyrrolinyl, pyrrolidinyl, 1 -pyrrolidinyl, 2- pyrrolidinyl, 3-pyrrolidinyl, tetrahydrofuranyl, tetrahydrothiophenyl, pyrazolinyl, 2- pyrazolinyl, 3-pyrazolinyl, pyrazolidinyl, 2-pyrazolidinyl, 3-pyrazolidinyl, imidazolidinyl, 3- dioxalanyl, thiazolidinyl, isoxazolidinyl, 2-imidazolinyl and the like.

[0098] Examples of 6-membered non-aromatic heterocyclyl or heterocycloalkyl rings include piperidinyl, piperidinonyl, pyranyl, dihyrdopyranyl, tetrahydropyranyl, 2H pyranyl, 4H pyranyl, thianyl, thianyl oxide, thianyl dioxide, piperazinyl, diozanyl, 1 ,4-dioxinyl, 1 ,4- dithianyl, 1 ,3,5-triozalanyl, 1 ,3,5-trithianyl, 1 ,4-morpholinyl, thiomorpholinyl, 1 ,4- oxathianyl, triazinyl, 1 ,4-thiazinyl and the like.

[0099] Examples of 7-membered non-aromatic heterocyclyl or heterocycloalkyl rings include azepanyl, oxepanyl, thiepanyl and the like.

[0100] Non-aromatic heterocyclyl or heterocycloalkyl rings may also be bicyclic heterocyclyl rings such as linked ring systems (for example uridinyl and the like) or fused ring systems. Fused ring systems include non-aromatic 5-membered, 6- membered or 7-membered heterocyclyls fused to carbocyclic aromatic rings such as phenyl, napthyl, indenyl, azulenyl, fluorenyl, anthracenyl and the like. Examples of non- aromatic or heterocycloalkyl 5-membered, 6-membered or 7-membered heterocyclyls fused to carbocyclic aromatic rings include indolinyl, benzodiazepinyl, benzazepinyl, dihydrobenzofuranyl and the like.

[0101] The term “halo” refers to fluoro, chloro, bromo or iodo.

[0102] Unless otherwise defined, the term “optionally substituted” or “optional substituent” as used herein refers to a group which may or may not be further substituted with 1 , 2, 3, 4 or more groups, preferably 1 , 2 or 3, more preferably 1 or 2 groups, selected from the group consisting of Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, C3- scycloalkyl, hydroxyl, oxo, Ci ealkoxy, aryloxy, Ci ealkoxyaryl, halo, Ci ealkylhalo (such as CF3), Ci ealkoxyhalo (such as OCF3), carboxyl, esters, cyano, nitro, amino, substituted amino, disubstituted amino, acyl, ketones, substituted ketones, amides, aminoacyl, substituted amides, disubstituted amides, thiol, alkylthio, thioxo, sulfates, sulfonates, sulfinyl, substituted sulfinyl, sulfonyl, substituted sulfonyl, sulfonylamides, substituted sulfonamides, disubstituted sulfonamides, aryl, arylCi -ealkyl, heterocyclyl and heteroaryl wherein each alkyl, alkenyl, alkynyl, cycloalkyl, aryl and heterocyclyl and groups containing them may be further optionally substituted. Optional substituents in the case of heterocycles containing N may also include but are not limited to Ci ealkyl i.e. N-Ci aalkyl, more preferably methyl particularly N-methyl.

[0103] For optionally substituted “Ci -ealkyl”, “C2-ealkenyl” and “C2-ealkynyl”, the optional substituent or substituents are preferably selected from halo, aryl, heteroaryl, Cs-sheterocycloalkyl, Cs-scycloalkyl, Ci ealkoxy, hydroxyl, oxo, aryloxy, Ci ealkylhalo, Ci- ealkoxylhalo and carboxyl. Each of these optional substituents may also be optionally substituted with any of the optional substituents referred to above, where nitro, amino, substituted amino, cyano, heterocyclyl (including non-aromatic heterocyclyl and heteroaryl), Ci ealkyl, C2-eakenyl, C2-ealkynyl, Ci ealkoxyl, Ci ealkylhalo, Ci -ealkoxyhalo, halo, hydroxyl and carboxyl are preferred.

[0104] It will be understood that suitable derivatives of aromatic heterocyclyls containing nitrogen include N-oxides thereof.

[0105] In the case of hybrid naming of substituent radicals describing two moieties that may both form a bond attaching the radical to the rest of the compound, such as alkylamino and alkylaryl, no direction in the order of groups is intended, so the point of attachment may be to any of the moieties included in the hybrid radical. For example, the terms “alkylaryl” and “arylalkyl”, are intended to refer to the same group and the point of attachment may be via the alkyl or the aryl moiety (or both in the case of diradical species). The direction of attachment of such a hybrid radical may be denoted by inclusion of a bond, for example, “-alkylaryl” or “arylalkyl-" denotes that the point of attachment of the radical to the rest of the compound is via the alkyl moiety, and “alkylaryl-" or “-arylalkyl” denotes that the point of attachment is via the aryl moiety.

[0106] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0107] As used herein and in the appended claims, the singular forms “a”, “an” and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to “a salt” may include a plurality of salts and a reference to “at least one heteroatom” may include one or more heteroatoms, and so forth.

[0108] The term “and/or” can mean “and” or “or”.

[0109] The term “(s)” following a noun contemplates the singular or plural form, or both.

[0110] Various features of the invention are described with reference to a certain value, or range of values. These values are intended to relate to the results of the various appropriate measurement techniques, and therefore should be interpreted as including a margin of error inherent in any particular measurement technique. Some of the values referred to herein are denoted by the term “about” to at least in part account for this variability. The term “about”, when used to describe a value, may mean an amount within ±10%, ±5%, ±1 % or ±0.1 % of that value.

Formula (I)

[0111] The invention provides compounds of formula (I):

A compound of formula (I): wherein: i) R ¹ is selected from optionally substituted Ci ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca- cycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted C1- ealkylaryl, optionally substituted Ci-ealkyl-Cs- cycloalkyl, optionally substituted Ci -ealkylheteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl, and R ² is selected from hydrogen, optionally substituted Ci ealkyl, optionally substituted C2-6alkenyl, optionally substituted C2-6alkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci- ealkoxyhalo; or ii) R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl; and

R ³ is selected from hydrogen, halo, optionally substituted C-i-ealkyl, optionally substituted C2-6alkenyl, optionally substituted C2-6alkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci- ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted Ci-4alkyl, or

R ^a and R ^b together form =0; and with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted Ca-gcycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs- heterocycloalkyl, and when R ¹ is phenyl and R ² is ethyl, R ³ is not Ci -ealkoxyhalo, optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0112] Advantageously, as described herein and shown in the Examples, the compounds of formula (I) are capable of binding to both wild type TSPO and A147T mutant TSPO. Accordingly, in some embodiments, the compound of formula (I) associates with one or both, preferably both, of wild-type TSPO and A147T mutant TSPO. In some embodiments, the compound of formula (I) has a high binding affinity for one or both, preferably both, of wild type TSPO and A147T mutant TSPO. The term “high binding affinity” encompasses binding affinities suitable for imaging TSPO. For example, a compound of formula (I) may have a binding affinity (Ki) of less than about 30 nM, preferably less than about 25 nM, more preferably less than about 20 nM, for one or both, preferably both, of wild type TSPO and A147T mutant TSPO.

[0113] In some embodiments, i) R ¹ is selected from optionally substituted Ci ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca-iocycloalkyl, optionally substituted heteroaryl and optionally substituted Ca-ioheterocycloalkyl, and

R ² is selected from optionally substituted Ci ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo; or ii) R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl; and

R ³ is selected from hydrogen, halo, optionally substituted Ci ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted C1- ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted Ci-4alkyl, or

R ^a and R ^b together form =0; and with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted C3-9cycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-ioheterocycloalkyl, and when R ¹ is phenyl and R ² is ethyl, R ³ is not Ci -ealkoxyhalo, optionally radiolabelled with a radionuclide.

R ¹ [0114] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted Cs-ealkenyl, optionally substituted Cs-ealkynyl, optionally substituted aryl, optionally substituted Ca- cycloalkyl, optionally substituted heteroaryl and optionally substituted Ca-ioheterocycloalkyL

[0115] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Cs- cycloalkyl, optionally substituted heteroaryl, optionally substituted Cs- heterocycloalkyl, and optionally substituted Ci ealkylaryl.

[0116] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Cs-scycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-wheterocycloalkyl.

[0117] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted aryl, optionally substituted Cs-wcycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-wheterocycloalkyl.

[0118] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted aryl, optionally substituted Cs-scycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-wheterocycloalkyl.

[0119] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl and optionally substituted C2-ealkynyl.

[0120] In some embodiments, R ¹ is selected from optionally substituted aryl, optionally substituted Cs-wcycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-ioheterocycloalkyL In some embodiments, R ¹ is selected from optionally substituted aryl and optionally substituted Cs-iocycloalkyL In some embodiments, R ¹ is selected from optionally substituted heteroaryl and optionally substituted Cs- ioheterocycloalkyL

[0121] In some embodiments, R ¹ is selected from optionally substituted aryl, optionally substituted Cs-wcycloalkyl and optionally substituted heteroaryl.

[0122] In some embodiments, R ¹ is an optionally substituted Ci-ealkyl. In some embodiments, R ¹ is an optionally substituted Ci-4alkyl. The Ci-ealkyl may be optionally optionally substituted ethyl, or optionally substituted butyl, including optionally substituted /-butyl. In some embodiments, R ¹ is an optionally substituted branched C3- ealkyl. The branched Cs ealkyl may be optionally substituted /-butyl.

[0123] In some embodiments, R ¹ is an optionally substituted C2-6alkenyl.

[0124] In some embodiments, R ¹ is an optionally substituted C2-6alkynyl.

[0125] In some embodiments, R ¹ is an optionally substituted aryl. The optionally substituted aryl may be a 6-membered or a 10-membered aryl. In some embodiments, the optionally substituted aryl is an optionally substituted phenyl. In some embodiments, R ¹ is phenyl.

[0126] In some embodiments, R ¹ is an optionally substituted Ci ealkylaryl. The aryl of the optionally substituted Ci -ealkylaryl may be a 6-membered aryl (such as phenyl) or a 10-membered aryl (such as naphthyl). In some embodiments, R ¹ is an optionally substituted Ci-4alkylaryl, preferably an optionally substituted Ci-2alkylaryl. In some embodiments, R ¹ is an optionally substituted Ci alkylaryl. In some embodiments, R ¹ is an optionally substituted C2alkylaryl. In some embodiments, R ¹ is an optionally substituted Ca-iocycloalkyl, preferably an optionally substituted C3-9cycloalkyl, more preferably an optionally substituted Cs-scycloalkyl, even more preferably an optionally substituted Cs-ecycloalkyl,. The optionally substituted cycloalkyl may be monocyclic or polycyclic. The optionally substituted cycloalkyl may be bridged. The optionally substituted cycloalkyl may be fused. In some embodiments, the optionally substituted cycloalkyl is monocyclic. In some embodiments, the optionally substituted cycloalkyl is polycyclic. In some embodiments, the optionally substituted cycloalkyl may be an optionally substituted bridged cycloalkyl. The cycloalkyl may be optionally substituted adamantyl, optionally substituted cubanyl, optionally substituted bicyclo[1 ,1 ,1]pentanyl, optionally substituted bicyclo[2,2,1 ]heptanyl or optionally substituted bicyclo[2,2,2]octanyl. In some embodiments, the cycloalkyl is not optionally substituted adamantyl. In some embodiments, the cycloalkyl is not bridged.

[0127] In some embodiments, R ¹ is an optionally substituted heteroaryl. The optionally substituted heteroaryl may be monocyclic or polycyclic (e.g., fused bicyclic). The optionally substituted heteroaryl may be a 5- membered monocyclic heteroaryl, 6- membered monocyclic heteroaryl, 9-membered fused bicyclic heteroaryl or I Q- membered fused bicyclic heteroaryl. The optionally substituted heteroaryl may comprise 1 , 2, 3 or more, preferably 1 , 2 or 3, more preferably 1 or 2, heteroatoms selected from N, O and S. The heteroatom of the optionally substituted heteroaryl may be N. The heteroatom of the optionally substituted heteroaryl may be O. The heteroatom of the optionally substituted heteroaryl may be S. Where the heteroaryl is polycyclic (e.g., fused bicyclic), the ring heteroatom(s) may be in 1 or more rings, and any ring may be connected to the amide nitrogen atom of formula (I). The heteroaryl may be optionally substituted pyridyl, optionally substituted pyrimidyl, optionally substituted benzo[ ]oxazolyl, optionally substituted benzo[ ][1 ,3]dioxazolyl, optionally substituted indolyl, optionally substituted indazolyl, optionally substituted quinolinyl, or optionally substituted isoquinolinyl. In some embodiments, R ¹ is an optionally substituted monocyclic heteroaryl. In some embodiments, R ¹ is not an optionally substituted fused bicyclic heteroaryl.

[0128] In some embodiments, R ¹ is an optionally substituted Ca-ioheterocycloalkyl (non-aromatic heterocyclyl). The optionally substituted heterocycloalkyl may be monocyclic or polycyclic. The optionally substituted heterocycloalkyl may be bridged. The optionally substituted heterocycloalkyl may comprise 1 , 2, 3 or more, preferably 1 , 2 or 3, more preferably 1 or 2, heteroatoms selected from N, O and S. The heteroatom of the optionally substituted heterocycloalkyl may be N. The heteroatom of the optionally substituted heterocycloalkyl may be O. The heteroatom of the optionally substituted heterocycloalkyl may be S.

[0129] In some embodiments, R ¹ is selected from optionally substituted Ci ealkyl when R ^a and R ^b are not both hydrogen; and optionally substituted aryl, optionally substituted heteroaryl and optionally substituted Ca-iocycloalkyl.

[0130] In some embodiments, R ¹ is selected from optionally substituted Ci ealkyl when R ^a and R ^b are not both hydrogen.

[0131] In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted aryl, optionally substituted C3-9cycloalkyl, optionally substituted heteroaryl and optionally substituted Cs- heterocycloalkyl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted branched Csealkyl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted aryl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted Ci- ealkylaryl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted Ca-gcycloalkyl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted heteroaryl. In some embodiments, when R ^a and R ^b are both hydrogen, R ¹ is optionally substituted Ca-ioheterocycloalkyl.

[0132] In some embodiments, R ¹ is selected from the group consisting of:

[0133] In some embodiments, R ¹ is selected from the group consisting of:

[0134] In some embodiments, R ¹ is selected from the group consisting of:

[0135] In some embodiments, R ¹ is selected from the group consisting of:

[0136] In some embodiments, R ¹ is optionally substituted with 1 , 2, 3, 4 or more groups selected from aryl, Ci ealkoxy (e.g., methoxy), halo, hydroxy, Ci -ealkyl (e.g., methyl), Ci-ealkylhalo (e.g., CF3), Ca-ecycloalkyl, -NH2, -NHCi-ealkyl, -N(Ci-6alkyl)2, - NHCOC1 -ealkyl, -CONHCi-ealkyl, -NHCONH2, -COOH, -C(O)OCi- ₆ alkyl, -C(O)Ci- ₆ alkyl and cyano.

R ²

[0137] In some embodiments, R ² is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci -ealkoxy and optionally substituted C1- ealkoxyhalo.

[0138] In some embodiments, R ² is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci -ealkoxy and optionally substituted C1- ealkoxyhalo.

[0139] In some embodiments, R ² is an optionally substituted Ci-ealkyl. In some embodiments, the optionally substituted Ci-ealkyl is an optionally substituted methyl or ethyl, preferably an optionally substituted methyl. In some embodiments, R ² is an optionally substituted C2-ealkenyl. In some embodiments, R ² is an optionally substituted C2-ealkynyl. In some embodiments, R ² is an optionally substituted Ci-ealkylhalo. In some embodiments, R ² is optionally substituted Ci-ealkoxy. In some embodiments, R ² is optionally substituted Ci -ealkoxyhalo. [0140] In some embodiments, R ² is optionally substituted Ci -ealkyl or optionally substituted Ci-ealkylhalo. In some embodiments, R ² is optionally substituted Ci ealkyl.

[0141] In some embodiments, R ² is Ci ealkyl or Ci-ealkylhalo. In some embodiments, R ² is Ci-ealkyl.

[0142] In some embodiments, R ² is hydrogen. In some embodiments, R ² is not hydrogen.

[0143] In some embodiments, R ² is methyl or ethyl, preferably methyl.

R ¹ and R ²

[0144] Any embodiment of R ¹ and/or R ² described herein may be combined.

[0145] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca-iocycloalkyl, optionally substituted heteroaryl and optionally substituted Ca-ioheterocycloalkyl, and

R ² is selected from optionally substituted Ci-ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci -ealkoxy and optionally substituted Ci -ealkoxyhalo.

[0146] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted aryl, optionally substituted Cs- cycloalkyl, optionally substituted heteroaryl and optionally substituted Cs- heterocycloalkyl, and

R ² is selected from optionally substituted Ci-ealkyl.

[0147] In some embodiments, R ¹ is optionally substituted aryl or optionally substituted Ci -ealkylaryl and R ² is hydrogen. In some embodiments, R ¹ is optionally substituted aryl and R ² is hydrogen. In some embodiments, R ¹ is optionally substituted Ci ealkylaryl and R ² is hydrogen.

[0148] In some embodiments, R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ci ealkylaryl, optionally substituted C3- cycloalkyl, optionally substituted heteroaryl and optionally substituted C3- ioheterocycloalkyl, and

R ² is selected from hydrogen, optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo; wherein, when R ² is hydrogen, R ¹ is optionally substituted aryl or optionally substituted Ci -ealkylaryl.

[0149] In some embodiments, R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl. The optionally substituted heterocyclyl may be fused, bridged or monocyclic. The optionally substituted heteroaryl may be fused or monocyclic.

[0150] In some embodiments, R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl.

[0151] In some embodiments, R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heteroaryl. Preferably, the optionally substituted heteroaryl is fused.

[0152] In some embodiments, R ¹ and R ² together with the nitrogen atom to which they are attached form a group selected from:

R ³

[0153] In some embodiments, R ³ is selected from halo, optionally substituted C1- ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo.

[0154] In some embodiments, R ³ is selected from halo, optionally substituted Ci- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo. [0155] In some embodiments, R ³ is selected from optionally substituted Ci ealkoxy and optionally substituted Ci-ealkoxyhalo.

[0156] In some embodiments, R ³ is selected from Ci ealkoxy and Ci-ealkoxyhalo.

[0157] In some embodiments, R ³ is selected from methoxy and C2alkoxyhalo. In some embodiments, R ³ is a methoxy. In some embodiments, R ³ is C2alkoxyhalo. In some embodiments, R ³ is -CH2CH2F.

[0158] In some embodiments, the halo of the halo, alkylhalo or alkoxyhalo at R ³ , is a fluoro.

R ^a and R ^b

[0159] In some embodiments, R ^a and R ^b are independently selected from hydrogen and optionally substituted Ci-4alkyl. In some embodiments, R ^a and R ^b are each independently optionally substituted Ci-4alkyl. In some embodiments, R ^a and R ^b are each hydrogen.

[0160] In some embodiments, R ^a and R ^b together form =0.

Radionuclide

[0161] The compound of formula (I) may be optionally radiolabelled with a radionuclide. The radionuclide may advantageously allow for detection of a radiolabelled compound, and consequently the location and/or distribution of TSPO as the compounds of the invention are capable of specific binding to TSPO.

[0162] The radionuclide may be any radionuclide suitable for use in nuclear medicine, such as nuclear medicine tomographic imaging. The radionuclide may allow a radiolabelled compound of the invention to be detected, for example by a radionuclide scan. In some embodiments, the radionuclide is a positron-emitting radioisotope, which may be detected by positron emission tomography (PET). In some embodiments, the radionuclide is a gamma-emitting isotope, which may be detected by single-photon emission computed tomography (SPECT).

[0163] In some embodiments, the compound of formula (I) is radiolabelled with a radionuclide selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br. In some embodiments, the compound of formula (I) is radiolabelled with ¹¹ C or ¹⁸ F. In some embodiments, the compound of formula (I) is radiolabelled with ¹¹ C. In some embodiments, the compound of formula (I) is radiolabelled with ¹⁸ F.

[0164] The compound of formula (I) may be radiolabelled at any suitable position. In some embodiments, the compound of formula (I) is radiolabelled at any one of R ¹ , R ² or R ³ , preferably R ³ . In some embodiments, the compound of formula (I) is radiolabelled at R ¹ or R ³ . In some embodiments, the compound of formula (I) is radiolabelled at R ² or R ³ . In some embodiments, the compound of formula (I) is radiolabelled at R ¹ . In some embodiments, the compound of formula (I) is radiolabelled at R ² . In some embodiments, the compound of formula (I) is radiolabelled at R ³ . In some embodiments, the compound of formula (I) is radiolabelled at optionally substituted heterocyclyl or optionally substituted heteroaryl formed by R ¹ and R ² together with the nitrogen atom to which they are attached.

[0165] General methods for the introduction of radionuclides are known to those skilled in the art. One method for the introduction of ¹¹ C is described in M. L. James et al. Bioorganic and Medicinal Chemistry 2005, 13, 6188-6194. One method for the introduction of ¹⁸ F is described in M. L. James et al., Journal of Nuclear Medicine 2008, 49, 814-822. These methods may be followed or adapted to provide radiolabelled compounds of the invention.

Additional formulae

[0166] In some embodiments, the compound of formula (I) is provided as a compound of formula (la): wherein R ¹ , R ² , R ³ , R ^a and R ^b are as defined herein, radiolabelled with a radionuclide as defined herein, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0167] In some embodiments of the compound of formula (la), R ² is a radiolabelled substituent selected from Ci-ealkyl- ¹⁸ F or a [ ¹¹ C]-labelled Ci ealkyL

[0168] In some embodiments of the compound of formula (la), R ¹ is a radiolabelled substituent selected from a ¹⁸ F substituted or ¹¹ C-labelled derivative of any R ¹ group described herein.

[0169] In some embodiments of the compound of formula (la), R ³ is a radiolabelled substituent selected from a ¹⁸ F substituted or ¹¹ C-labelled derivative of any R ³ group described herein.

[0170] In some embodiments, the compound of formula (I) is provided as a compound of formula (lb): wherein R ¹ , R ² , R ³ , R ^a and R ^b are as defined herein, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0171] In some embodiments, the compound of formula (I) is provided as a compound of formula (Ic): wherein R ¹ , R ² and R ³ are as defined herein, optionally radiolabelled with a radionuclide as defined herein, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0172] In some embodiments, R ³ is radiolabelled.

[0173] In some embodiments, the compound of formula (I) is provided as a compound of formula (Ic1 ): wherein R ¹ and R ² are as defined herein, wherein R ⁴ is optionally substituted Ci -ealkyl or optionally substituted Ci ealkyhalo, optionally radiolabelled with a radionuclide as defined herein, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0174] In some embodiments, R ⁴ is optionally substituted C-i-ealkyl, preferably Ci- aalkyl, more preferably methyl. In some embodiments, R ⁴ is optionally substituted Ci- ealkyhalo, preferably Ci aalkyhalo, more preferably -CH2CH2F.

[0175] In some embodiments, R ⁴ is radiolabelled.

[0176] In some embodiments, the compound of formula (I) is provided as a compound of formula (Ic2) : wherein R ¹ and R ³ are as defined herein, optionally radiolabelled with a radionuclide as defined herein, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0177] In some embodiments, R ³ is radiolabelled.

Compounds

[0178] The compound of formula (I) may be selected from any one or more of the compounds included in Table 1 .

Table 1. Compounds of formula (I) or a radiolabelled derivative thereof, or a a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0179] In some embodiments, the compound of the invention is selected from any one or more of compounds 1 -23. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 -13. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 -5, 7-9, 11 - 13, 15 and 17-22. In some embodiments, the compound of the invention is selected from any one or more of compounds 6, 10, 14, 16 and 23. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 -10, 12-14 and 16-23. In some embodiments, the compound of the invention is selected from any one or more of compounds 11 and 15. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 , 2 and 4-23. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 , 2 and 4-13. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 , 3-8 and 10-23. In some embodiments, the compound of the invention is selected from any one or more of compounds 2 and 9. In some embodiments, the compound of the invention is selected from any one or more of compounds 1 -13 and 15-31 . [0180] In some embodiments, the compound of the invention is a radiolabelled derivative of any of compounds 1 -23, such as a ¹⁸ F or ¹¹ C analogue of compounds 1 -23. In some embodiments, the compound of the invention is a radiolabelled derivative of any of identified groups of compounds selected from Table 1 .

Preparation

[0181] In another aspect, there is also provided a process for preparing a compound of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0182] Typically, the compounds of the invention may be prepared by techniques known in the art.

[0183] In some embodiments, a compound of formula (I) is prepared from a compound of formula (III): wherein R ^3a is selected from hydrogen, hydroxy, halo, optionally substituted C-i-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci ealkylhalo, optionally substituted Ci ealkoxy and optionally substituted Ci -ealkoxyhalo, or a salt or solvate thereof.

[0184] In some embodiments, R ^3a is as defined for R ³ herein.

[0185] In some embodiments, a compound of formula (III) is used to prepare a compound of formula (I) where R ^a and R ^b are each hydrogen. In some embodiments, a compound of formula (I) where R ^a and R ^b are each hydrogen is prepared by converting the carboxylic acid of the compound of formula (III) to an activated carboxylic acid (e.g., by contacting a compound of formula (III) with a chlorinating agent such as oxalyl chloride), and subsequently contacting with a compound of formula (IV): R ¹ ' R ² (|V) wherein R ¹ and R ² are as defined herein, or a salt or solvate thereof.

[0186] In some embodiments, a compound of formula (I) is prepared by a compound of formula (V): wherein R ¹ and R ² are as defined herein, or a salt or solvate thereof.

[0187] In some embodiments, a compound of formula (V) is used to prepare a compound of formula (I) where R ^a and R ^b are each hydrogen and where R ³ is optionally substituted Ci -ealkoxy or optionally substituted Ci -ealkoxyhalo, for example a compound of formula (Ic1 ). In some embodiments, a compound of formula (I) where R ^a and R ^b are each hydrogen and where R ³ is optionally substituted Ci-ealkoxy or optionally substituted Ci -ealkoxyhalo, for example a compound of formula (Ic1 ), is prepared by contacting a compound of formula (VI):

Z-R ⁴ (VI) wherein Z is a leaving group, preferably a sulfonate ester (for instance, tosyl, mesyl, nosyl, triflyl, etc.) or halo, more preferably halo, wherein R ⁴ is as defined herein, or a salt or solvate thereof, under basic conditions. [0188] In some embodiments, a compound of formula (I) is prepared from a compound of formula (VII) wherein R ³ is as defined herein, or a salt or solvate thereof.

[0189] In some embodiments, a compound of formula (VII) is used to prepare a compound of formula (I) where R ^a and R ^b together form =0. In some embodiments, a compound of formula (I) where R ^a and R ^b together form =0 is prepared by contacting a compound of formula (VII) with oxalyl chloride and subsequently contacting with a compound of formula (IV).

[0190] Further, compounds of the invention which are radiolabelled may be prepared by techniques known in the art. For example, a compound of formula (I) which is radiolabelled with a radionuclide selected from ¹¹ C, ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br may be prepared by incorporating the radionuclide as a substituent in one of the starting materials or in an intermediate used in the synthesis of the compound of formula (I). As another example, a compound of formula (I) which is radiolabelled with a radionuclide selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br may be prepared by techniques known in the art for modifying an organic compound to replace a hydrogen or halo group in that compound with ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l or ⁷⁵ Br.

[0191] In compounds labelled with a radionuclide, the radionuclide may be susceptible to decay and may have a relatively short half-life. For this reason, radiolabelled compounds may need to be prepared shortly before their intended use (e.g., before administering to a subject and detecting in v/vo via a radionuclide scan), so that the radiolabelled compound may be used within the expected lifetime of the radionuclide. Ideally, a radiolabelled compound is prepared from a precursor by a minimal number of reaction steps, which may allow for efficient preparation of the radiolabelled compound.

[0192] In one aspect, there is provided a compound of formula (Ila): wherein: iii) R ¹ is selected from optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca- cycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs- heterocycloalkyl, and

R ² is selected from optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci ealkylhalo, optionally substituted Ci ealkoxy and optionally substituted Ci ealkoxyhalo; or iv) R ¹ and R ² together with the nitrogen atom to which they are attached form an optionally substituted heterocyclyl or optionally substituted heteroaryl; and

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ¹ is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs ealkyl, optionally substituted aryl, optionally substituted C3- cycloalkyl, optionally substituted heteroaryl, optionally substituted C3- ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci -ealkyl- Cs-iocycloalkyl, optionally substituted Ci -ealkyl heteroaryl, and optionally substituted Ci-ealkyl-C3-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof. [0193] In some embodiments of formula (Ila), R ¹ is selected from optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted Ca-iocycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-ioheterocycloalkyl.

[0194] In some embodiments, the compound of formula (Ila) is used to prepare a compound of formula (I), which is radiolabelled with a radionuclide at R ³ . In some embodiments, the radionuclide is selected from ¹¹ C, ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹¹ C and ¹⁸ F. In some embodiments, the radionuclide is ¹¹ C. In some embodiments, the radionuclide is selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹⁸ F.

[0195] J ¹ may be any moiety suitable for introducing a radionuclide into the compound, for example via a substitution reaction, such that it provides a compound of formula (I) as described herein radiolabelled at R ³ . In some embodiments, J ¹ is selected from hydroxy, halo, Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci- ealkoxyhalo, and wherein said Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci- ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ¹ is selected from hydroxy, halo, Ci-ealkyl, C2- ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, and wherein said Ci- ealkyl, C2-ealkenyl, C2-ealkynyl, Ci -ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ¹ is selected from hydroxy, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci -ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ¹ is selected from hydroxy, Ci -ealkoxy and Ci-ealkoxyhalo, wherein said Ci -ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ¹ is selected from Ci-ealkoxy and Ci- ealkoxyhalo, wherein said Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ¹ is selected from Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci -ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ¹ is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and is optionally further substituted. In some embodiments, J ¹ is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. Preferably, the Ci-ealkoxy is methoxy. In some embodiments, J ¹ is hydroxy.

[0196] In one aspect, there is provided a compound of formula (lib): wherein:

R ² is selected from hydrogen, optionally substituted Ci -ealkyl, optionally substituted C2- ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo;

R ³ is selected from hydrogen, halo, optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted C1- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ² is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, J ² is selected from hydrogen, optionally substituted branched Cs-ealkyl, optionally substituted aryl, Ca-iocycloalkyl, optionally substituted heteroaryl, optionally substituted Ca-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci -ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0197] In some embodiments of formula (lib), R ² is selected from optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci-ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci -ealkoxyhalo.

[0198] In some embodiments of formula (lib), when R ^a and R ^b are both hydrogen, J ² is selected from hydrogen, optionally substituted branched Ce-ealkyl, aryl, C3- wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl, wherein said Ci -ealkyl, Cs-ealkenyl, C2- ealkynyl, aryl, Cs-wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I.

[0199] In some embodiments, the compound of formula (lib) is used to prepare a compound of formula (I), which is radiolabelled with a radionuclide at R ¹ . In some embodiments, the radionuclide is selected from ¹¹ C, ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹¹ C and ¹⁸ F. In some embodiments, the radionuclide is ¹¹ C. In some embodiments, the radionuclide is selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹⁸ F.

[0200] J ² may be any moiety suitable for introducing a radionuclide into the compound, for example via a substitution reaction, such that it provides a compound of formula (I) as described herein radiolabelled at R ¹ . In some embodiments, J ² is selected from hydrogen, Ci ealkyl, Cs-ealkenyl, Cs-ealkynyl, aryl, Ci -ealkylaryl, Cs-wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl, wherein said Ci ealkyl, Cs-ealkenyl, Cs-ealkynyl, aryl, Ci -ealkylaryl, Cs-wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ² is selected from hydrogen, Ci ealkyl, Cs-ealkenyl, Cs-ealkynyl, aryl, Cs-wcycloalkyl, heteroaryl and Cs- wheterocycloalkyl, wherein said Ci ealkyl, Cs-ealkenyl, Cs-ealkynyl, aryl, Cs-wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ² is hydrogen. In some embodiments, J ² is selected from Ci -ealkyl, Cs-ealkenyl, C2- ealkynyl, aryl, Ci -ealkylaryl, Cs-wcycloalkyl, heteroaryl and Cs-wheterocycloalkyl, wherein said Ci -ealkyl, Cs-ealkenyl, Cs-ealkynyl, aryl, Ci -ealkylaryl, Cs-wcycloalkyl, heteroaryl and Ca-ioheterocycloalkyl are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ² is selected from Ci -ealkyl, C2-ealkenyl, C2-ealkynyl, aryl, C3- cycloalkyl, heteroaryl and Cs-wheterocycloalkyl, wherein said Ci ealkyl, C2-ealkenyl, C2- ealkynyl, aryl, Cs- cycloalkyl, heteroaryl and Cs-wheterocycloalkyl are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ² is selected from hydroxy, Ci-ealkoxy and Ci ealkoxyhalo, wherein said Ci-ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ² is selected from hydroxy, C1- ealkoxy and Ci -ealkoxyhalo, wherein said Ci-ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ² is selected from Ci-ealkoxy and Ci -ealkoxyhalo, wherein said Ci -ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ² is selected from Ci-ealkoxy and Ci -ealkoxyhalo, wherein said Ci -ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ² is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and is optionally further substituted. In some embodiments, J ² is Ci-ealkoxy, wherein said Ci- ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. Preferably, the Ci-ealkoxy is methoxy..

[0201] In some embodiments where R ^a and R ^b are both hydrogen, J ² is a moiety that is capable of modification to introduce a radionuclide into the compound and J ² is selected from hydrogen, optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted Cs-ecycloalkyl, optionally substituted heteroaryl and optionally substituted Cs-ioheterocycloalkyl.

[0202] In one aspect, there is provided a compound of formula (He): wherein:

R ¹ is selected from optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl or optionally substituted C2-ealkynyl, optionally substituted aryl, optionally substituted C3- cycloalkyl, optionally substituted heteroaryl, optionally substituted C3- ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci ealkyl- Cs-iocycloalkyl, optionally substituted Ci -ealkyl heteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl,

R ³ is selected from hydrogen, halo, optionally substituted Ci ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted C1- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted C1- 4alkyl, or

R ^a and R ^b together form =0, and

J ³ is a moiety that is capable of modification to introduce a radionuclide into the compound; with the proviso that when R ^a and R ^b are both hydrogen, R ¹ is selected from optionally substituted branched Cs-ealkyl, optionally substituted aryl, optionally substituted C3- gcycloalkyl, optionally substituted heteroaryl, optionally substituted Cs-ioheterocycloalkyl, optionally substituted Ci -ealkylaryl, optionally substituted Ci-ealkyl-Cs-iocycloalkyl, optionally substituted Ci -ealkylheteroaryl, and optionally substituted Ci-ealkyl-Cs-ioheterocycloalkyl, or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0203] In some embodiments of formula (He), R ¹ is selected from optionally substituted Ci -ealkyl, optionally substituted C2-ealkenyl or optionally substituted C2- ealkynyl, optionally substituted aryl, optionally substituted Ca-iocycloalkyl, optionally substituted heteroaryl and optionally substituted Ca-ioheterocycloalkyL

[0204] In some embodiments, the compound of formula (He) is used to prepare a compound of formula (I), which is radiolabelled with a radionuclide at R ² . In some embodiments, the radionuclide is selected from ¹¹ C, ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹¹ C and ¹⁸ F. In some embodiments, the radionuclide is ¹¹ C. In some embodiments, the radionuclide is selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹⁸ F.

[0205] J ³ may be any moiety suitable for introducing a radionuclide into the compound, for example via a substitution reaction, such that it provides a compound of formula (I) as described herein radiolabelled at R ¹ . In some embodiments, J ³ is selected from hydrogen, Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci- ealkoxyhalo, wherein said Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ³ is selected from hydrogen, Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci -ealkyl, C2-ealkenyl, C2- ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ³ is hydrogen. In some embodiments, J ³ is selected from Ci-ealkyl, C2- ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci- ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ³ is selected from Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci- ealkoxyhalo, wherein said Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ³ is selected from hydroxy, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci-ealkoxy and Ci- ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ³ is selected from hydroxy, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ³ is selected from Ci-ealkoxy and Ci ealkoxyhalo, wherein said Ci-ealkoxy and Ci- ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ³ is selected from Ci-ealkoxy and Ci ealkoxyhalo, wherein said Ci- ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ³ is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and is further substituted. In some embodiments, J ³ is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. Preferably, the Ci-ealkoxy is methoxy.

[0206] In one aspect, there is provided a compound of formula (lid): wherein:

A is an optionally substituted heterocyclyl or optionally substituted heteroaryl; wherein A includes J ⁴ as part of the heterocyclic or heteroaryl ring or a substituent on the heterocyclic or heteroaryl ring;

R ³ is selected from hydrogen, halo, optionally substituted Ci-ealkyl, optionally substituted C2-ealkenyl, optionally substituted C2-ealkynyl, optionally substituted Ci- ealkylhalo, optionally substituted Ci-ealkoxy and optionally substituted Ci-ealkoxyhalo;

R ^a and R ^b are each independently selected from hydrogen and optionally substituted Ci- 4alkyl, or

R ^a and R ^b together form =0; and J ⁴ is a moiety that is capable of modification to introduce a radionuclide into the compound; or a salt, solvate, tautomer, N-oxide or stereoisomer thereof.

[0207] In some embodiments, the compound of formula (lid) is used to prepare a compound of formula (I), which is radiolabelled with a radionuclide as part of the heterocyclic or heteroaryl ring or a substituent on the heterocyclic or heteroaryl ring at A. In some embodiments, the radionuclide is selected from ¹¹ C, ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹¹ C and ¹⁸ F. In some embodiments, the radionuclide is ¹¹ C. In some embodiments, the radionuclide is selected from ¹⁸ F, ¹²³ 1, ⁷⁶ Br, ¹²⁴ l and ⁷⁵ Br, preferably ¹⁸ F.

J ⁴ may be any moiety suitable for introducing a radionuclide into the compound, for example via a substitution reaction, such that it provides a compound of formula (I) as described herein radiolabelled with a radionuclide as part of the heterocyclic or heteroaryl ring or a substituent on the heterocyclic or heteroaryl ring at A. In some embodiments, J ⁴ is selected from hydrogen, hydroxy, halo, C-i-ealkyl, C2-ealkenyl, C2- ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci -ealkyl, C2- ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ⁴ is selected from hydrogen, hydroxy, Ci -ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci- ealkoxyhalo, wherein said Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ⁴ is hydrogen. In some embodiments, J ⁴ is hydroxy. . In some embodiments, J ⁴ is halo. In some embodiments, J ⁴ is selected from Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci-ealkyl, C2-ealkenyl, C2-ealkynyl, C1- ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ⁴ is selected from Ci-ealkyl, C2- ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo, wherein said Ci- ealkyl, C2-ealkenyl, C2-ealkynyl, Ci-ealkylhalo, Ci-ealkoxy and Ci-ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ⁴ is selected from hydroxy, Ci-ealkoxy and Ci -ealkoxyhalo, wherein said Ci-ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ⁴ is selected from hydroxy, Ci-ealkoxy and Ci ealkoxyhalo, wherein said Ci-ealkoxy and Ci ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ⁴ is selected from Ci-ealkoxy and Ci- ealkoxyhalo, wherein said Ci-ealkoxy and Ci ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and are optionally further substituted. In some embodiments, J ⁴ is selected from Ci-ealkoxy and Ci ealkoxyhalo, wherein said Ci -ealkoxy and Ci -ealkoxyhalo are substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. In some embodiments, J ⁴ is Ci-ealkoxy, wherein said Ci-ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I; and is optionally further substituted. In some embodiments, J ⁴ is Ci-ealkoxy, wherein said Ci -ealkoxy is substituted with at least one group selected from tosylate, mesylate, tributylstannane, trimethylsilyl, Br and I. Preferably, the Ci-ealkoxy is methoxy.

Applications

[0208] As described herein, compounds of the invention are capable of specifically binding to TSPO with high affinity. Accordingly, a compound of the invention, particularly a compound which is radiolabelled, may be useful for detecting and/or imaging TSPO.

[0209] In one aspect, there is provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for detecting TSPO. The presence of a signal from the radiolabelled compound indicates the presence of TSPO.

[0210] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for imaging TSPO.

[0211] In another aspect, there is provided a method of determining the distribution and/or extent of TSPO expression in a subject, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject; and detecting a signal from the compound in the subject.

[0212] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the subject, wherein the TSPO expression is correlated with the signal from the compound.

[0213] In another aspect, there is provided a method of determining the distribution and/or extent of TSPO expression in a subject in need thereof, comprising administering to the subject a radiolabelled compound of formula (I) or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, and then subjecting the subject to an imaging technique capable of detecting an emission from the radiolabelled compound of formula (I) to thereby determine the distribution and/or extent of TSPO expression in the subject.

[0214] In some embodiments, the methods described herein may comprise imaging the compound of formula (I), for example by positron emission tomography (PET) imaging or single-photon emission computerized tomography (SPECT) imaging. Imaging may be used, for example, to identify the location and/or quantify the level of TSPO expression.

[0215] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for determining the distribution and/or extent of TSPO expression in a subject. The presence of a signal from the radiolabelled compound indicates the distribution and/or extent of TSPO expression in the subject.

[0216] In embodiments of methods and uses described herein that involve detecting a compound of the invention, the compound of formula (I) may be detected by performing a radionuclide scan. Accordingly, in some embodiments, detecting a signal from the compound comprises performing a radionuclide scan. The radionuclide scan may be suitably selected depending on the radionuclide present in the compound. In some embodiments, the radionuclide scan is a positron emission tomography (PET) scan or a single-photon emission computerized tomography (SPECT) scan. [0217] TSPO is a biomarker of neuroinflammation. Subjects having neuroinflammation, or are susceptible to developing neuroinflammation, typically have elevated levels of TSPO expression in the brain, relative to a subject without neuroinflammation. A compound of the invention, particularly a compound which is radiolabelled, may therefore be useful for detecting elevated levels of TSPO and/or neuroinflammation in a subject.

[0218] Accordingly, in one aspect, there is provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for detecting elevated levels of TSPO expression by detecting a signal from the compound. Typically, little to no signal will be detected where TSPO expression levels are not elevated (e.g., in a subject with no neuroinflammation), whereas a signal will be detected where TSPO expression is elevated (e.g., in a subject with neuroinflammation). Therefore, the presence of a signal from the radiolabelled compound indicates elevated levels of TSPO expression.

[0219] In another aspect, there is provided a method for detecting neuroinflammation in a subject, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject; and detecting a signal from the compound in the subject.

[0220] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO binding of the compound in the brain parenchyma of the subject, wherein elevated levels of TSPO binding of the compound indicates neuroinflammation.

[0221] In some embodiments, the method further comprises imaging the detected compound of formula (I), for example by positron emission tomography (PET) imaging or single-photon emission computerized tomography (SPECT) imaging.

[0222] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for detecting neuroinflammation in a subject. The presence of a signal from the radiolabelled compound indicates neuroinflammation in the subject.

[0223] In another aspect, there is provided a method of diagnosing neuroinflammation in a subject, the method comprising: administering a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to a subject in need thereof; and subjecting the subject to an imaging technique capable of detecting an emission from the radiolabelled compound of formula (I).

[0224] There is also provided the use of a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a diagnostic agent or a diagnostic composition for diagnosing neuroinflammation in a subject.

[0225] There is also provided the use of a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for diagnosing neuroinflammation in a subject.

[0226] In another aspect, there is provided a method of treating neuroinflammation, comprising: administering a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to a subject in need thereof; subjecting the subject to an imaging technique capable of detecting an emission from the radiolabelled compound of formula (I); and optionally administering an anti-neuroinflammatory drug to the subject.

[0227] In another aspect, there is provided a method of treating neuroinflammation, comprising: administering a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to a subject in need thereof; subjecting the subject to an imaging technique capable of detecting an emission from the radiolabelled compound of formula (I); and optionally administering an anti-neuroinflammatory drug to the subject.

[0228] In another aspect, there is provided a method of treating neuroinflammation, comprising: administering a radiolabelled compound of formula (I), or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to a subject in need thereof; subjecting the subject to an imaging technique capable of detecting an emission from the radiolabelled compound of formula (I); and optionally ceasing administration to the subject of an anti-neuroinflammatory drug.

[0229] In these methods, the neuroinflammatory drug may be any suitable anti- neuroinflammatory drug as are known in the art, and/or any compound of formula (I) as described herein, and may be administered by any means and within the typical dosage range and regimen as are known in the art. In these methods, whether the step of administering, adjusting the dose of or ceasing administration of the neuroinflammatory drug may be carried out depending on the distribution and/or extent of TSPO expression determined by the imaging technique, for example if the distribution and/or extent of TSPO expression suggest neuroinflammation the methods typically involve administering the anti-neuroinflammatory drug, while if the distribution and/or extent of TSPO expression suggest insubstantial neuroinflammation and the subject had received anti-neuroinflammatory treatment the methods may include adjustment of or cessation of administration of the anti-neuroinflammatory drug.

[0230] Neuroinflammatory processes are typically associated with central nervous system (CNS) disorders and neurodegenerative disorders, including neuropsychiatric disorders. The compounds of the invention may be useful for diagnosis, treatment and/or clinical investigation (e.g., monitoring progression of a disease, disorder or condition) of such disorders in a subject.

[0231] In one aspect, there is provided a method for diagnosing a CNS disorder or neurodegenerative disorder in a subject, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject; and detecting a signal from the compound in the subject.

[0232] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound, and wherein elevated levels of TSPO expression indicates the central nervous system (CNS) disorder and/or the neurodegenerative disorder.

[0233] In some embodiments, the method further comprises imaging the detected compound of formula (I), for example by positron emission tomography (PET) imaging or single-photon emission computerized tomography (SPECT) imaging.

[0234] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a diagnostic agent or a diagnostic composition for diagnosing a CNS disorder and/or neurodegenerative disorder in a subject.

[0235] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for diagnosing a CNS disorder and/or neurodegenerative disorder in a subject.

[0236] There is also provided a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for use in diagnosing a CNS disorder and/or neurodegenerative disorder in a subject.

[0237] In another aspect, there is provided a method for treating a CNS disorder and/or a neurodegenerative disorder, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject; detecting a signal from the compound in the subject; and administering a compound of formula (I), which is optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject.

[0238] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound.

[0239] In another aspect, there is provided a method of treating a CNS disorder and/or a neurodegenerative disorder, the method comprising administering to a subject in need thereof a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0240] There is also provided the use of a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N- oxide and/or stereoisomer thereof, in the manufacture of a medicament, a diagnostic agent, a pharmaceutical composition and/or a diagnostic composition for treating a CNS disorder and/or a neurodegenerative disorder.

[0241] There is also provided the use of a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N- oxide and/or stereoisomer thereof, for treating a CNS disorder and/or a neurodegenerative disorder.

[0242] There is also provided a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for use in treating a CNS disorder and/or a neurodegenerative disorder.

[0243] In another aspect, there is provided a method of monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a CNS and/or neurodegenerative disorder, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject during the treatment regimen; and detecting a signal from the compound in the subject.

[0244] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound.

[0245] The method may be carried out repeatedly during the course of the treatment regimen. The drug to treat a CNS and/or neurodegenerative disorder may be a compound of the invention or another agent useful for treating a CNS and/or neurodenegerative disorder.

[0246] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a diagnostic agent or a diagnostic composition for monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a CNS and/or neurodegenerative disorder.

[0247] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a CNS and/or neurodegenerative disorder.

[0248] There is also provided a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for use in monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a CNS and/or neurodegenerative disorder.

[0249] The CNS and neurodegenerative disorders may be any disease, disorder or condition associated with neuroinflammation and/or elevated levels of TSPO expression. In some embodiments, the CNS disorder and/or neurodegenerative disorder are selected from Alzheimer’s disease, dementia, Parkinson’s disease, Huntington’s disease, multiple sclerosis, major depressive disorder, anxiety, obsessive compulsive disorder, bipolar disorder, schizophrenia, amyotrophic lateral sclerosis, multiple system atrophy, epilepsy, encephalopathy, inflammation, infection, stroke and a brain tumour.

[0250] In another aspect, there is provided a method of diagnosing a disease, condition and/or disorder associated with TSPO in a subject, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof to the subject; and detecting a signal from the compound in the subject.

[0251] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound, and wherein elevated levels of TSPO expression indicates the disease, condition and/or disorder associated with TSPO.

[0252] In some embodiments, the method further comprises imaging the detected compound of formula (I), for example by positron emission tomography (PET) imaging or single-photon emission computerized tomography (SPECT) imaging.

[0253] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a diagnostic agent or a diagnostic composition for diagnosing a disease, condition and/or disorder associated with TSPO in a subject.

[0254] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for diagnosing a disease, condition and/or disorder associated with TSPO in a subject.

[0255] There is also provided a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for use in diagnosing a disease, condition and/or disorder associated with TSPO in a subject.

[0256] In another aspect, there is provided a method for modulating TSPO activity, the method comprising administering to a subject in need thereof an effective amount of a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0257] Without wishing to be bound by theory, it is believed that the compounds of the invention bind to TSPO, and it is through this binding to TSPO that the activity of TSPO is modulated. It is therefore believed that through this, modulation of any disease, condition and/or disorder associated with TSPO activity and/or mediated by TSPO may be treated with the compounds for formula (I).

[0258] The present invention therefore includes methods and uses of the compounds described herein, for the treatment of any disease, disorder or condition associated with elevated levels of TSPO expression, or for which TSPO modulation would be beneficial.

[0259] Accordingly, in one aspect, there is provided a method for treating a disease, condition and/or disorder associated with modulation of TSPO in a subject, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject; detecting a signal from the compound in the subject; and administering a compound of formula (I), which is optionally radiolabelled, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject.

[0260] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound.

[0261] In another aspect, there is provided a method for treating a disease, condition and/or disorder associated with modulation of TSPO, the method comprising administering to a subject in need thereof a compound of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof.

[0262] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a medicament or a pharmaceutical composition for treating a disease, condition and/or disorder associated with modulation of TSPO.

[0263] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for treating a disease, condition and/or disorder associated with modulation of TSPO.

[0264] In another aspect, there is provided a method of monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a disease, condition and/or disorder associated with modulation of TSPO, the method comprising: administering a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, to the subject during the treatment regimen; and detecting a signal from the compound in the subject.

[0265] In some embodiments, the method further comprises determining the distribution and/or extent of TSPO expression in the brain parenchyma of the subject, wherein the TSPO expression is correlated with the signal from the compound.

[0266] In some embodiments, the method further comprises imaging the detected compound of formula (I), for example by positron emission tomography (PET) imaging or single-photon emission computerized tomography (SPECT) imaging. This imaging may be dynamic imaging.

[0267] The method may be carried out repeatedly during the course of the treatment regimen. The drug to treat a disease, condition and/or disorder associated with modulation of TSPO may be a compound of the invention or another agent useful for treating a disease, condition and/or disorder associated with modulation of TSPO.

[0268] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, in the manufacture of a diagnostic agent or a diagnostic composition for monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a disease, condition and/or disorder associated with modulation of TSPO.

[0269] There is also provided the use of a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a disease, condition and/or disorder associated with modulation of TSPO.

[0270] There is also provided a compound of formula (I), which is radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, for use in monitoring the extent and/or distribution of TSPO expression in a subject who is receiving a treatment regimen comprising a drug to treat a disease, condition and/or disorder associated with modulation of TSPO.

[0271] The disease, condition and/or disorder associated with modulation of TSPO may be any CNS disorder and/or neurodegenerative disorder as described herein.

[0272] In some embodiments of the methods and uses described herein, the subject has elevated levels of TSPO expression, for example in the brain. The elevated levels of TSPO expression may be attributed to upregulated expression of TSPO, for example in the brain, in the subject.

[0273] In some embodiments of the methods and uses described herein, detection of the compound in the subject is commenced immediately after initial administration of compound. This is preferred for the collection of quantitative data. In some embodiments of the methods and uses described herein, detection of the compound in the subject is commenced after a delay after initial administration of compound. This may be to improve tissue localisation. In some embodiments, this delay may be from about 5 min to about 1 h. In some embodiments, this delay may be about 5 min, about 10 min, about 20 min, about 30 min, about 45 min or about 1 h.

[0274] In some embodiments of the methods and uses described herein, detection of the compound in the subject proceeds for from about 0.5 to about 3 half-lives of the radionuclide labelling the compound, preferably for about 1 half-life. In some embodiments of the methods and uses described herein, preferably wherein the radionuclide is ¹⁸ F, detection of the compound in the subject proceeds for from about 30 min to about 6 h, preferably from about 1 h to about 3 h. In some embodiments of the methods and uses described herein, preferably wherein the radionuclide is ¹⁸ F, detection of the compound in the subject proceeds for about 2 h. In some embodiments of the methods and uses described herein, preferably wherein the radionuclide is ¹¹ C, detection of the compound in the subject proceeds for from about 5 min to about 1 h, preferably from about 10 min to about 40 min. In some embodiments of the methods and uses described herein, preferably wherein the radionuclide is ¹¹ C, detection of the compound in the subject proceeds for about 20 min.

[0275] Advantageously, as described herein and as shown in the Examples, compounds of the invention are capable of binding with high affinity to both wild type TSPO and A147T mutant TSPO. Wild type and A147T mutant TSPO are the most commonly found isoforms of TSPO. The compounds of the invention may be useful for administration to a subject (e.g., for imaging TSPO or for diagnosing or treating a disease associated with TSPO), without needing to genotype the subject before administration and/or imaging.

[0276] In some embodiments of the methods and uses described herein, the subject expresses one or both, preferably both, of wild-type TSPO and A147T mutant TSPO.

[0277] In some embodiments, following administration to the subject, the compound of the invention associates with one or both, preferably both, of wild-type TSPO and A147T mutant TSPO.

[0278] In some embodiments, the compound of the invention is administered, or formulated for administration, without regard to the TSPO genotype of the subject. In some embodiments, the TSPO genotype of the subject is not determined prior to administering a compound of the invention. [0279] In embodiments of the methods and uses described herein that involve detecting a compound of the invention, the compound may be administered, or formulated for administration, in a detectable amount. As used herein, the term “detectable amount” means that the amount of the compound is sufficient to enable detection of binding of the compound to TSPO.

[0280] In embodiments of the methods and uses herein that involve imaging a compound of the invention, the compound may be administered, or formulated for administration, in an imaging effective amount. As used herein, the term “imaging effective amount” means that the amount of the compound is sufficient to enable imaging of the compound bound to TSPO.

[0281] It will be appreciated that in embodiments of the methods and uses described herein that involve detecting and/or imaging a compound of the invention, the compound of formula (I) is preferably radiolabelled with a radionuclide.

[0282] In embodiments of the methods and uses described herein that involve treating a disease, disorder and/or condition with a compound of the invention, the compound may be administered, or formulated for administration, in an effective amount. As used herein, the term "effective amount" means that amount of a drug or pharmaceutical agent that will elicit the biological or medical response of a tissue, system, animal or human that is being sought, for instance, by a researcher or clinician. Furthermore, the term "therapeutically effective amount" means any amount which, as compared to a corresponding subject who has not received such amount, results in improved treatment, healing, prevention, or amelioration of a disease, disorder, or side effect, or a decrease in the rate of advancement of a disease or disorder. The term also includes within its scope amounts effective to enhance normal physiological function.

[0283] The salts of the compounds of formula (I), optionally radiolabelled with a radionuclide, are preferably pharmaceutically acceptable, but it will be appreciated that non-pharmaceutically acceptable salts also fall within the scope of the present disclosure, for example, as these may be useful as intermediates in the preparation of pharmaceutically acceptable salts or in methods not requiring administration to a subject. [0284] The term “pharmaceutically acceptable” may be used to describe any salt, solvate, tautomer, N-oxide and/or stereoisomer thereof, or any other compound which upon administration to a subject, is capable of providing (directly or indirectly) a compound of formula (I), optionally radiolabelled with a radionuclide, or an active metabolite or residue thereof and typically that is not deleterious to the subject.

[0285] Suitable pharmaceutically acceptable salts include, but are not limited to, salts of pharmaceutically acceptable inorganic acids such as hydrochloric, sulphuric, phosphoric, nitric, carbonic, boric, sulfamic, and hydrobromic acids, or salts of pharmaceutically acceptable organic acids such as acetic, propionic, butyric, tartaric, maleic, hydroxymaleic, fumaric, malic, citric, lactic, mucic, gluconic, benzoic, succinic, oxalic, phenylacetic, methanesulphonic, toluenesulphonic, benzenesulphonic, salicylic, sulphanilic, aspartic, glutamic, edetic, stearic, palmitic, oleic, lauric, pantothenic, tannic, ascorbic and valeric acids.

[0286] Base salts include, but are not limited to, those formed with pharmaceutically acceptable cations, such as sodium, potassium, lithium, calcium, magnesium, zinc, ammonium, alkylammonium such as salts formed from triethylamine, alkoxyammonium such as those formed with ethanolamine and salts formed from ethylenediamine, choline or amino acids such as arginine, lysine or histidine. General information on types of pharmaceutically acceptable salts and their formation is known to those skilled in the art and is as described in general texts such as “Handbook of Pharmaceutical salts’’ P.H. Stahl, C.G.Wermuth, 1st edition, 2002, Wiley-VCH.

[0287] In the case of compounds that are solids, it will be understood by those skilled in the art that the inventive compounds, agents and salts may exist in different crystalline or polymorphic forms, all of which are intended to be within the scope of the present invention and specified formulae.

[0288] The invention includes all crystalline forms of a compound of formula (I), optionally radiolabelled with a radionuclide, including anhydrous crystalline forms, hydrates, solvates and mixed solvates. If any of these crystalline forms demonstrates polymorphism, all polymorphs are within the scope of this invention.

[0289] Formula (I) is intended to cover, where applicable, solvated as well as unsolvated forms of the compounds. Thus, formula (I) includes compounds having the indicated structures, optionally radiolabelled with a radionuclide, including the hydrated or solvated forms, as well as the non-hydrated and non-solvated forms.

[0290] The compounds of formula (I), optionally radiolabelled with a radionuclide, or salts, tautomers, N-oxides or polymorphs thereof may be provided in the form of solvates. Solvates contain either stoichiometric or non-stoichiometric amounts of a solvent, and may be formed during the process of crystallization with pharmaceutically acceptable solvents such as water, alcohols such as methanol, ethanol or isopropyl alcohol, DMSO, acetonitrile, dimethyl formamide (DMF), acetic acid, and the like with the solvate forming part of the crystal lattice by either non-covalent binding or by occupying a hole in the crystal lattice. Hydrates are formed when the solvent is water, alcoholates are formed when the solvent is alcohol. Solvates of the compounds of the present invention can be conveniently prepared or formed during the processes described herein. In general, the solvated forms are considered equivalent to the unsolvated forms for the purposes of the invention.

[0291] Basic nitrogen-containing groups may be quarternised with such agents as Ci- ealkyl halide, such as methyl, ethyl, propyl, and butyl chlorides, bromides and iodides; dialkyl sulfates like dimethyl and diethyl sulfate; and others.

[0292] Nitrogen containing groups may also be oxidised to form an N-oxide.

[0293] The compound of formula (I), optionally radiolabelled with a radionuclide, or salts, tautomers, N-oxides and/or solvates thereof that form crystalline solids may demonstrate polymorphism. All polymorphic forms of the compounds, salts, tautomers, N-oxides and/or solvates are within the scope of the invention.

[0294] The compound of formula (I), optionally radiolabelled with a radionuclide, may demonstrate tautomerism. Tautomers are two interchangeable forms of a molecule that typically exist within an equilibrium. Any tautomers of the compounds of formula (I) are to be understood as being within the scope of the invention.

[0295] The compound of formula (I), optionally radiolabelled with a radionuclide, may contain one or more stereocentres. All stereoisomers of the compounds of formula (I) are within the scope of the invention. Stereoisomers include enantiomers, diastereomers, geometric isomers (E and Zolephinic forms and cis and trans substitution patterns) and atropisomers. In some embodiments, the compound is a stereoisomerically enriched form of the compound of formula (I) at any stereocentre. The compound may be enriched in one stereoisomer over another by at least about 60, 70, 80, 90, 95, 98 or 99%.

[0296] The compound of formula (I), optionally radiolabelled with a radionuclide, or its salts, tautomers, solvates, N-oxides, and/or stereoisomers, may be isotopically enriched with one or more of the isotopes of the atoms present in the compound. For example, the compound may be enriched with one or more of the following minor isotopes: ² H, ³ H, ¹³ C, ¹⁴ C, ¹⁵ N and/or ¹⁷ O. An isotope may be considered enriched when its abundance is greater than its natural abundance.

[0297] In some embodiments, the compounds of the invention may be administered to a subject in the form of a prodrug. A "prodrug" is a compound that may not fully satisfy the structural requirements of the compounds provided herein, but is modified in vivo, following administration to a subject or patient, to produce a compound of formula (I) provided herein. For example, a prodrug may be an acylated derivative of a compound as provided herein. Prodrugs include compounds wherein hydroxy, carboxy, amine or sulfhydryl groups are bonded to any group that, when administered to a mammalian subject, cleaves to form a free hydroxy, carboxy, amino, or sulfhydryl group, respectively. Examples of prodrugs include, but are not limited to, acetate, formate, phosphate and benzoate derivatives of alcohol and amine functional groups within the compounds provided herein. Prodrugs of the compounds provided herein may be prepared by modifying functional groups present in the compounds in such a way that the modifications are cleaved in vivo to generate the parent compounds.

[0298] Prodrugs include compounds wherein an amino acid residue, or a polypeptide chain of two or more (eg, two, three or four) amino acid residues which are covalently joined to free amino, and amido groups of compounds of formula (I). The amino acid residues include the 20 naturally occurring amino acids commonly designated by three letter symbols and also include, 4-hydroxyproline, hydroxylysine, demosine, isodemosine, 3-methylhistidine, norvlin, beta-alanine, gamma-aminobutyric acid, citrulline, homocysteine, homoserine, ornithine and methionine sulfone. Prodrugs also include compounds wherein carbonates, carbamates, amides and alkyl esters which are covalently bonded to the above substituents of formula (I) through the carbonyl carbon prodrug sidechain. [0299] Pharmaceutical compositions may be formulated from compounds according to formula (I), optionally radiolabelled with a radionuclide, for any appropriate route of administration including, for example, oral, rectal, nasal, vaginal, topical (including transdermal, buccal, ocular and sublingual), parenteral (including subcutaneous, intraperitoneal, intradermal, intravascular (for example, intravenous), intramuscular, spinal, intracranial, intrathecal, intraocular, periocular, intraorbital, intrasynovial and intraperitoneal injection, intracisternal injection as well as any other similar injection or infusion techniques), inhalation, insufflation, infusion or implantation techniques (e.g., as sterile injectable aqueous or non-aqueous solutions or suspensions).

[0300] In certain embodiments, compositions in a form suitable for parenteral use are preferred. For intravenous, intramuscular, subcutaneous, or intraperitoneal administration, one or more compounds may be combined with a sterile aqueous solution which is preferably isotonic with the blood of the recipient. Such formulations may be prepared by dissolving solid active ingredient in water containing physiologically compatible substances such as sodium chloride or glycine, and having a buffered pH compatible with physiological conditions to produce an aqueous solution, and rendering said solution sterile. The formulations may be present in unit or multi-dose containers such as sealed ampoules or vials. Examples of components are described in Martindale - The Extra Pharmacopoeia (Pharmaceutical Press, London 1993), and

Remington: The Science and Practice of Pharmacy, 21 st Ed., 2005, Lippincott Williams & Wilkins. All methods include the step of bringing the active ingredient, for example a compound defined by formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt thereof, into association with the carrier which constitutes one or more accessory ingredients. In general, the pharmaceutical compositions are prepared by uniformly and intimately bringing the active ingredient, for example a compound defined by formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt thereof, into association with a liquid carrier or a finely divided solid carrier or both, and then, if necessary, shaping the product into the desired formulation. In the pharmaceutical composition the active object compound is included in an amount sufficient to produce the desired effect. In some embodiments, the method of the invention comprises administering a pharmaceutical comprising a compound of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt or solvate thereof and a pharmaceutically acceptable carrier, diluent and/or excipient. [0301] In the context of this specification, the term “administering” and variations of that term including “administer” and “administration”, includes contacting, applying, delivering or providing a compound or composition of the invention to an organism, or a surface by any appropriate means.

[0302] For the modulation of TSPO, the dose of the biologically active compound according to the invention may vary within wide limits and may be adjusted to individual requirements. Active compounds according to the present invention are generally administered in a therapeutically effective amount. Compounds for detecting TSPO are generally administered in a detectable amount. Compounds for imaging TSPO are generally administered in an imaging effective amount. The daily dose may be administered as a single dose or in a plurality of doses. The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the subject treated and the particular mode of administration.

[0303] It will be understood, however, that the specific dose level for any particular subject will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex and diet of the subject, time of administration, route of administration, and rate of excretion, drug combination (i.e. other drugs being used to treat the subject), and the severity of the particular disorder undergoing therapy. Such treatments may be administered as often as necessary and for the period of time judged necessary by the treating physician. A person skilled in the art will appreciate that the dosage regimen, therapeutically effective amount, detectable amount and/or imaging effective amount of the compound of formula (I) to be administered may need to be optimized for each individual.

[0304] It will also be appreciated that different dosages may be required for diagnosing and/or treating different disorders.

[0305] The terms “treating”, “treatment” and “therapy” are used herein to refer to curative therapy, prophylactic therapy and preventative therapy. Thus, in the context of the present disclosure the term “treating” encompasses curing, ameliorating or tempering the severity of the disease, condition and/or disorder associated with modulation of TSPO, or their symptoms. [0306] “Preventing” or “prevention” encompasses preventing the occurrence of disease, condition and/or disorder associated with modulation of TSPO or their symptoms, or tempering the severity of the disease, condition and/or disorder associated with modulation of TSPO, or their symptoms, if symptoms exhibit subsequent to the administration of the compounds or pharmaceutical compositions of the present invention.

[0307] “Subject” includes any human or non-human animal. Thus, in addition to being useful for human treatment, the compounds of the present invention may also be useful for veterinary treatment of mammals, including companion animals and farm animals, such as, but not limited to dogs, cats, horses, cows, sheep, and pigs.

[0308] The compounds of the present invention may be administered together with a pharmaceutical carrier, diluent and/or excipient as described above.

[0309] In some embodiments, the compound of the invention may be administered in combination with a further active pharmaceutical ingredient (API). The API may be any that is suitable for treating any of the diseases, conditions and/or disorders associated with TSPO, such as those described herein. The compound of the invention may be coformulated with the further API in any of the pharmaceutical compositions described herein, or the compound of the invention may be administered in a concurrent, sequential or separate manner. Concurrent administration includes administering the compound of the invention at the same time as the other API, whether coformulated or in separate dosage forms administered through the same or different route. Sequential administration includes administering, by the same or different route, the compound of the invention and the other API according to a resolved dosage regimen, such as within about 0.5, 1 , 2, 3, 4, 5, or 6 hours of the other. When sequentially administered, the compound of the invention may be administered before or after administration of the other API. Separate administration includes administering the compound of the invention and the other API according to regimens that are independent of each other and by any route suitable for either active, which may be the same or different.

[0310] The methods may comprise administering the compound of formula (I), optionally radiolabelled with a radionuclide, in any pharmaceutically acceptable form. In some embodiments, the compound of formula (I) is provided in the form of a pharmaceutically acceptable salt, solvate, N-oxide, polymorph or tautomer thereof, or a combination of these forms in any ratio.

[0311] The methods may also comprise administering a pharmaceutical composition comprising the compound of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, N-oxide, polymorph or tautomer thereof to the subject in need thereof. The pharmaceutical composition may comprise any pharmaceutically acceptable carrier, diluent and/or excipient described herein.

[0312] The methods may also comprise administering a diagnostic composition comprising the compound of formula (I), preferably radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, N-oxide, polymorph or tautomer thereof to the subject in need thereof. The diagnostic composition may comprise any pharmaceutically acceptable carrier, diluent and/or excipient described herein.

[0313] The compounds of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, N-oxide, polymorph or tautomer or thereof, may be administered by any suitable means, for example, orally, rectally, nasally, vaginally, topically (including buccal and sub-lingual), parenterally, such as by subcutaneous, intraperitoneal, intravenous, intramuscular, or intracisternal injection, inhalation, insufflation, infusion or implantation techniques (e.g., as sterile injectable aqueous or non-aqueous solutions or suspensions). In some embodiments, the compound of formula (I) is administered, or formulated for administration, parenterally.

[0314] The compounds of the invention may be provided as pharmaceutical compositions and/or diagnostic compositions including those for oral, rectal, nasal, topical (including buccal and sub-lingual), parenteral administration (including intramuscular, intraperitoneal, sub-cutaneous and intravenous), or in a form suitable for administration by inhalation or insufflation. The compounds of formula (I), or a pharmaceutically acceptable salt thereof, together with a conventional adjuvant, carrier or diluent, may thus be placed into the form of pharmaceutical compositions and unit dosages thereof, and in such form may be employed as solids, such as tablets or filled capsules, or liquids as solutions, suspensions, emulsions, elixirs or capsules filled with the same, all for oral use, or in the form of sterile injectable solutions for parenteral (including subcutaneous) use. Kits

[0315] Also provided is a kit of parts, the kit comprising in separate parts: a compound of formula (I), optionally radiolabelled with a radionuclide, or a pharmaceutically acceptable salt, solvate, N-oxide, polymorph or tautomer thereof; and instructions for its use in any of the methods or uses of the invention.

[0316] There is also provided a kit comprising in separate parts: a compound of formula (Ila) or formula (lib) or formula (He) or formula (lid), or a salt, solvate, tautomer and/or stereoisomer thereof; and instructions for its use in any of the methods or uses of the invention.

Examples

[0317] The compounds, compositions, kits, methods and uses described herein are described by the following illustrative and non-limiting examples.

General Experimental

[0318] Unless otherwise stated, all reactions were performed under an atmosphere of nitrogen and all solvents and reagents were used as purchased from commercial sources. Anhydrous solvents dichloromethane, tetrahydrofuran and N,N- dimethylformamide were obtained from a PureSolv MD 7 solvent purification system (Innovative Technology, Inc.). Analytical thin-layer chromatography (TLC) was performed using Merck aluminium-backed silica gel 60 F254 (0.2 mm) plates and visualised under shortwave (254 nm) and/or longwave (365 nm) ultraviolet light as well as with potassium permanganate, bromocresol green, ninhydrin and vanillin stains.

Flash column chromatography was performed using Merck silica gel pore size 60 A, 40- 63 pm, 230-400 mesh with eluent mixtures reported as volume to volume (v/v) ratios or percentages. Nuclear magnetic resonance spectra were recorded using a Bruker NEO 300 MHz NMR Spectrometer (300 MHz), Bruker AVIII 400 MHz NMR Spectrometer, or Bruker AVIII 500 MHz NMR Spectrometer at 300 K. ¹ H chemical shifts are expressed as parts per million (ppm) with residual chloroform (5 7.26) or dimethyl sulfoxide (5 2.50) as reference and are reported as chemical shift (5); relative integral; multiplicity (s = singlet, bs = broad singlet, d = doublet, dd = doublet of doublets, dt = doublet of triplets, t= triplet, q = quartet, m = multiplet); coupling constants (J) reported in Hz; assignment. ¹³ C chemical shifts are expressed as parts per million (ppm) with residual chloroform (5 77.16) as a reference and reported as chemical shift (5). Low-resolution mass spectra (LRMS) were recorded using electrospray ionisation (ESI) recorded on a Bruker AmaZon SL ion trap spectrometer. High resolution mass spectrometry (HRMS) was performed by Dr Nicholas Proschogo on a Bruker Apex Qe 7T Fourier Transform Ion Cyclotron Resonance mass spectrometer equipped with an Apollo II ESI/MALDI dual source. Samples were run with syringe infusion at 150 pL/h on a Cole Palmer syringe pump into the ESI source. High performance liquid chromatography (HPLC) analysis of organic purity was conducted on a Waters Alliance 2695 instrument using a SunFireTM C18 column (5 pm, 2.1 x 150 mm) and detected using a Waters 2996 photodiode array (PDA) detector set at 254 nm. Separation was achieved using water (solvent A) and acetonitrile (solvent B) at a flow rate of 0.2 mL/min with a gradient of 0% B to 100% B over 30 minutes. HPLC data is reported as percentage purity and retention time (RT) in minutes.

Example 1 : Synthesis

General Description of chemistry

[0319] Scheme 1 shows a general synthesis of the compounds of the invention. An alkyl 4-alkoxybenzoate can be converted to its corresponding p-ketonitrile (step 1 ) in the presence of acetonitrile and base, such as potassium tert-butoxide, in the presence of solvent, such as THF. The p-ketonitrile can be alkylated to form an alkylated p- ketonitrile (step 2) by treatment with an acetate ester, where the acetate is substituted with a leaving group such as a halide, after contacting the p-ketonitrile with base, such as NaH, in the presence of a solvent such as THF, at reduced temperatures, such as 0 °C. Alternatively, the alkylated p-ketonitrile may be reacted with an acetate amide, to introduce the amide functionality of the compounds of formula (I). The alkylated p- ketonitrile ester can be cyclised form an aminopyrazole ester (step 3) by treatment with hydrazine in the presence of acid, such as acetic acid, and solvent, such as t-butanol. The aminopyrazole ester can be cyclised to form a pyrazolopyrimidine ester (step 4) through treatment with pentane-2, 4-dione in the presence of solvent, such as ethanol, at elevated temperatures, for instance, under reflux. The ester of the pyrazolopyrimidine ester can be be deprotected (step 5) to form a pyrazolopyrimidine acid via routes known to one skilled in the art. For instance, a /-butyl ester can be deprotected to an acid under basic conditions such as sodium hydroxide in the presence of solvent, such as THF and methanol.

[0320] The pyrazolopyrimidine acid can be converted to an activated pyrazolopyrimidine ester or acid halide. For instance, a pyrazolopyrimidine acid can be converted to a pyrazolopyrimidine acid halide (step 6a) using a halogenating agent, such as oxalyl chloride, at reduced temperatures, such as 0 °C, in the presence of a nucleophilic catalyst, such as N,N-dimethylformamide, and solvent, such as dichloromethane, before allowing the reaction mixture to warm, for example to ambient temperatures. The pyrazolopyrimidine acid halide may be coupled to form a fused indole product via routes known to one skilled in the art, such as via amide coupling reagents (step 7a). For example, under step 7a, the pyrazolopyrimidine acid chloride may be converted to a pyrazolopyrimidine product using an amine in the presence of an amide coupling reagent, such as A/,A/-diisopropylethylamine, and a nucleophilic catalyst, such as 4-(dimethylamino)pyridine, in the presence of a solvent, such as dichloromethane. Alternatively, the pyrazolopyrimidine acid may be coupled to form a pyrazolopyrimidine product via routes known to one skilled in the art, such as via amide coupling reagents (step 6b). Under step 6b, the pyrazolopyrimidine acid may be converted to a pyrazolopyrimidine product using an amide coupling reagent, such as PyBOP, under basic conditions, such as in the presence of triethylamine, in solvent, such as DMF; in the presence of an amine. An alternative reagent system under step 6b is the use of the amide coupling reagent EEDQ in the presence of the base triethylamine in the solvent THF and the presence of an amine, at elevated temperatures, such as reflux.

[0321] Alternatively, for oxoacetamido derivatives (ie where R ^a and R ^b together form =0) the p-ketonitrile of step 1 can be cyclised to form a pyrazolopyrimidine (step 2i) by treatment with hydrazine in the presence of solvent, such as ethanol, at elevated temperatures, for instance, 80 °C; followed by treatment with acetylacetone and acid, such as acetic acid, at elevated temperatures, for instance, 80 °C. The pyrazolopyrimidine can be converted to an oxoacetamido pyrazolopyrimidine product (step 3i) using oxalyl chloride in the presence of solvent, such as dichloromethane, and base, such as DIPEA; followed by treatment with base, such as pyridine, in solvent, such as THF, in the presence of amine.

Scheme 1

1. oxalyl chloride, base

Synthesis of intermediates

[0322] Scheme 2 shows the synthesis of Intermediates A1 -A4. Scheme 2

Intermediate A4

Intermediate A1 :

[0323] Methyl 4-methyoxybenzoate (10.0 g, 60.2 mmol, 1 .00 equiv.), potassium tert- butoxide (14.81 g, 130 mmol, 2.20 equiv.) and acetonitrile (15.6 mL, 300 mmol, 5.00 equiv.) were dissolved in tetrahydrofuran (250 mL) and stirred at room temperature for 12 hrs. This mixture was filtered, rinsed with ice cold tetrahydrofuran (50 mL) and the collected solid was redissolved in deionised water (100 mL). Concentrated hydrochloric acid was added dropwise until pH < 2 and a white precipitate had formed. This was extracted using dichloromethane (100 mL). The organic layer was washed with saturated aqueous sodium bicarbonate solution (2 x 50 mL) and brine (50 mL). The organic layer was dried with magnesium sulfate and solvent was removed in vacuo to yield Intermediate A1 as a yellow solid (9.19 g, 85%). ¹ H NMR (300 MHz, CDCh) 5 7.90 (d, 2H), 6.98 (d, 2H), 4.01 (s, 2H), 3.90 (s, 3H); ¹³ C NMR (500 MHz, CDCh) 5 185.52, 164.89, 132.35, 131.09 127.45, 114.49, 55.81 , 29.16; LRMS (+ESI) m/z: 198.02 [M+Na] ⁺ ; (-ESI) m/z: 173.85 [M-H]’. Intermediate A2:

[0324] Intermediate A1 (9.00 g, 51 .4 mmol, 1 .00 equiv.) was dissolved in tetrahydrofuran (350 mL) under a nitrogen atmosphere. To this sodium hydride (3.10 g, 77.0 mmol, 1 .50 equiv., 60 % w/w in mineral oil) was added portion-wise over 15 minutes while stirring. tert-Butyl 2-bromoacetate (9.09 mL, 62.0 mmol, 1 .2 equiv.) was then added and the mixture was left to stir for 48 hrs. Saturated aqueous ammonium chloride solution (250 mL) was added and aqueous layer extracted with ethyl acetate (5 x 100 mL). The organic layer was dried with magnesium sulfate, filtered, and the solvent was removed in vacuo. The crude solid that was purified by silica flash gel chromatography (5-15% ethyl acetate/hexane) to yield Intermediate A2 as colourless crystals (9.0 g, 85% yield). ¹ H NMR (400 MHz, CDCh) 5 8.08 (d, J = 8.9 Hz, 2H), 6.99 (d, J = 8.9 Hz, 2H), 4.66 (dd, J = 8.5 Hz, 5.5 Hz, 1 H) 3.90 (s, 3H), 3.17 (dd, J = 17.1 Hz, 8.5 Hz, 1 H), 2.84 (dd, J = 17.1 Hz, 5.5 Hz, 1 H), 1.44 (s, 9H); ¹³ C NMR (400 MHz, CDCh) 5 187.08, 168.82, 164.89, 131.55, 127.04, 117.00, 114.48, 82.51 , 55.80, 34.21 , 34.13, 28.12; LRMS (+ESI) m/z: 312.36 [M+Na] ⁺ , 601.13 [2M+Na] ⁺ .

Intermediate A3:

[0325] Intermediate A2 (4.70 g, 16.2 mmol, 1.00 equiv.), hydrazine monohydrate (1 .22 mL, 24.4 mmol, 1 .50 equiv.) and glacial acetic acid (1 .39 mL, 24.4 mmol, 1 .50 equiv.) were stirred in tert-butanol (20 mL) at room temperature for 1 hour. The reaction mixture was then heated to reflux and stirred for 4 hours. The solvent was removed from the mixture in vacuo to yield a crude solid. This was purified by silica gel flash chromatography (5% methanol/dichloromethane) to yield a yellow oil. Azeotropic distillations were performed with toluene (3 x 30 mL) to remove residual acetic acid and yield Intermediate A3 as a yellow oil (1.10g, 61%). ¹ H NMR (400 MHz, CDCh) 5 7.46 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.82 (s, 3H), 3.30 (s, 2H), 1 .46 (s, 9H); ¹³ C NMR (400 MHz, CDCh) 5 171 .47, 159.97, 154.36, 142.86, 129.12, 122.83, 114.49, 97.32, 81 .49, 55.45, 31 .09, 28.21 ; LRMS (+ESI) m/z: 304.11 [M+H] ⁺ , 326.11 [M+Na] ⁺ , 607.22 [2M+H] ⁺ , 629.23 [2M+Na] ⁺ .

Intermediate A4:

[0326] Intermediate A3 (1 .00 g, 5.01 mmol, 1 .00 equiv.) and pentane-2, 4-dione

(0.340 mL, 5.51 mmol, 1.10 equiv.) were refluxed in ethanol (20 mL) for 4 hours. The solvent was removed in vacuo to yield a yellow oil. Methanol (30 mL) was added, resulting in a precipitation of a white powder which was collected via filtration. The white powder was redissolved in tetrahydrofuran (20 mL) and methanol (20 mL), and sodium hydroxide (5 M, 2 mL, 10.02 mmol) was added. This mixture was heated at reflux overnight. The solvent was removed in vacuo. Concentrated hydrochloric acid (5 mL) was added dropwise until a yellow precipitate had formed (pH < 2). The precipitate was collected via filtration and washed with cold deionised water, leaving a white precipitate. This precipitate was resuspended in ethanol/ethyl acetate (1 :1 , 50 mL) and toluene (20 mL) was added. The solvent was removed in vacuo. The resulting crude solid was recrystallised from chloroform/methanol (1 :1 , 30 mL) to yield Intermediate A4 as a fine yellow powder (1 .44 g, 92%). ¹ H NMR (300 MHz, CDCh) 5 7.72 (d, J = 8.7 Hz, 2H), 7.04 (d, J = 8.7 Hz, 2H), 6.63 (s 1 H), 4.03 (s, 2H), 3.87 (s, 3H), 2.82 (s, 3H), 2.66 (s, 3H); ¹³ C NMR (500 MHz, CDCh) 5 172.52, 160.08, 154.92, 158.11 , 129.82, 126.11 , 114.31 , 108.59, 99.19, 55.49, 52.20, 31.07, 29.23, 24.74, 17.08; LRMS (+ESI) m/z: 312.14 [M+H] ⁺ , 334.10 [M+Na] ⁺ .

[0327] Scheme 3 shows the synthesis of Intermediates D1 -D3 and Intermediate B1 .

Intermediate B1 Intermediate D3

Intermediate D1 [0328] Methyl 4-isopropoxybenzoate (20.0 g, 102.9 mmol, 1 .0 eq) was dissolved in anhydrous tetrahydrofuran (400 mL) with stirring at room temperature. Potassium tert- butoxide (25.4 g, 257.4 mmol, 2.2 eq) was added in portions as a solid, followed immediately by addition of acetonitrile (26.9 mL, 514.9 mmol, 5.0 eq). The reaction mixture was stirring at room temperature for 16 hours, then diluted with water (150 mL) and washed with methylene chloride (2 x 250 mL). The aqueous layer was subsequently acidified to pH < 3 using 32% aqueous hydrochloric acid and extracted with ethyl acetate (3 x 250 mL). The combined organic layers were dried (MgSCU) and concentrated under reduced pressure to afford a crude brown crystalline residue. Recrystallisation from 1 :1 isopropyl alcohol/hexane yielded Intermediate D1 (8.5 g, 41%) as pale brown crystals. ¹ H NMR (300 MHz, CDCh) 5 7.87 (d, J= 8.9 Hz, 2H), 6.93 (d, J = 8.9 Hz, 2H), 4.67 (hept, J = 6.1 Hz, 1 H), 4.00 (s, 2H), 1.37 (d, J= 6.1 Hz, 6H). LRMS (+ESI) 204.14 (30 %, [M+H] ⁺ ), 226.14 (100 %, [M+Na] ⁺ ), 429.11 (51 %, [2M+Na] ⁺ ).

Intermediate D2

[0329] Intermediate D1 (7.9 g, 39.0 mmol, 1 .0 eq) was dissolved in anhydrous THF (200 mL) and cooled on an ice bath to 0 ^s C, before the addition of sodium hydride (60% w/w dispersion in mineral oil, 1 .6 g, 41 .0 mmol, 1 .05 eq) in four portions. The resulting reaction mixture was left to stir at 0 ^s C for 30 minutes. 2-bromo-A/-methyl-A/- phenylacetamide ³ (8.9 g, 39 mmol, 1 .0 eq) was subsequently added as a solid, and the reaction was left to stir with warming to room temperature for 16 hours [note: reaction mixture turned from pale yellow suspension to pale brown slurry]. The reaction mixture was quenched carefully with 1 M aqueous hydrochloric acid (300 mL), and extracted with ethyl acetate (3 x 100 mL). The combined organics layers were washed sequentially with saturated aqueous sodium bicarbonate (100 mL) and brine (100 mL), dried (MgSCU), and concentrated under reduced pressure to yield crude Intermediate D2 as an orange syrup which solidified on standing and was deemed of sufficient purity to carry through to subsequent steps without further purification. ¹ H NMR (300 MHz, CDCh) 5 8.00 (d, J = 8.9 Hz, 2H), 7.54 - 7.37 (m, 2H), 7.33 - 7.09 (m, 3H), 6.94 (d, J = 9.0 Hz, 2H), 4.92 (dd, J = 9.2, 4.7 Hz, 1 H), 4.66 (hept, J = 6.1 Hz, 1 H), 3.26 (s, 3H), 3.05 (dd, J= 16.5, 9.1 Hz, 1 H), 2.58 (dd, J = 16.5, 4.7 Hz, 1 H), 1.37 (d, J= 6.1 Hz, 6H). LRMS (+ESI) 373 (100%, [M+Na] ⁺ ).

Intermediate D3 [0330] To a solution of Intermediate D2 (13.6 g, 39.0 mmol, 1 .0 eq) in absolute ethanol (140 mL) was added hydrazine hydrate (3.8 mL, 78.0 mmol, 2.0 eq) followed by glacial acetic acid (3.7 mL, 58.5 mmol, 1 .5 eq). The reaction mixture was heated at reflux for 90 minutes, until no starting material remained by TLC analysis. Acetylacetone (6.0 mL, 58.5 mmol, 1 .5 eq) was added directly to the hot reaction mixture, which was stirred at reflux for 16 hours. After cooling to room temperature, the volatiles were removed under reduced pressure and the dark brown residue redissolved in methylene chloride (250 mL), followed by washing with saturated aqueous sodium bicarbonate (50 mL), water (50 mL), and brine (50 mL). The organic layer was dried (MgSC ) and partially decolourised with activated charcoal before being concentrated to a pale brown oil under reduced pressure. Recrystallisation from 3:1 hexane/toluene afforded GS-103 (9.3 g, 56% over three steps) as a fine white powder. ¹ H NMR (300 MHz, CDCh) 5 7.66 (d, J= 8.7 Hz, 2H), 7.45 - 7.25 (m, 5H), 6.97 (d, J= 8.8 Hz, 2H), 6.47 (s, 1 H), 4.62 (hept, J= 6.1 Hz, 1 H), 3.71 (s, 2H), 3.29 (s, 3H), 2.73 - 2.46 (m, 6H), 1 .37 (d, J= 6.0 Hz, 6H). ¹³ C NMR (75 MHz, CDCh) 5 171.15, 158.12, 157.40, 154.88, 147.73, 144.62, 144.25, 129.82, 129.63, 127.53, 126.12, 1 15.97, 108.12, 100.74, 69.94, 37.78, 29.27, 24.67, 22.07, 16.89.. LRMS (+ESI) 429.18 (100 %, [M+H] ⁺ ), 451.20 (67 %, [M+Na] ⁺ )

Intermediate B1

[0331] To Intermediate D3 (433 mg, 1 .0 mmol, 1 .0 eq) was added methanesulfonic acid (6.5 mL) at room temperature. The resulting solution was stirred at the same temperature for 30 minutes before basifying to pH ~8 with 28% aqueous ammonia. The resultant precipitate was isolated by vacuum filtration and dried under high-vacuum to yield Intermediate B1 (357 mg, 92%) as an off-white powder. Rt 0.25 (7.5% v/v methanol in dichloromethane); IR (vmax/cm ^-1 ) 3233, 1632, 1586, 1528, 1486, 1432, 1390, 1271 , 1231 , 1165, 1114, 839, 769, 702, 639, 565, 521 , 414; ¹ H NMR (300 MHz, CDCh) 5 7.72 (s, 1 H), 7.53 (d, J = 8.2 Hz, 2H), 7.41 - 7.26 (m, 5H), 6.86 - 6.75 (m, 2H), 6.45 (s, 1 H), 3.74 (s, 2H), 3.25 (s, 3H), 2.69 (s, 3H), 2.53 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.7, 157.6, 157.0, 155.2, 147.6, 144.8, 143.9, 129.8, 129.7, 127.6, 127.4, 125.2, 115.7, 108.2, 100.4, 37.9, 29.4, 24.5, 16.9; LRMS (+ESI) m/z: 387 ([M+H] ⁺ , 80%), 409 ([M+Na] ⁺ , 100%).

Intermediate D4

[0332] To Intermediate B1 (200 mg, 0.517 mmol, 1 eq.) in anhydrous DMF was added sodium hydride (22.76 mg, 60% w/w dispersion in mineral oil, 1.1 eq.) at 0 ^S C, which was warmed to ambient temperature and stirred for 1 h. 1 ,2-Bis(tosyloxy)ethane (229 mg, 1 .2 eq.) was added and the reaction mixture left to stir at room temperature for 3 h. The reaction mixture was diluted with ethyl acetate and washed with 5% aqueous lithium chloride, then dried over anhydrous magnesium sulfate and concentrated in vacuo. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (0.5-2% v/v) afforded Intermediate D4 (122 mg, 40%) as a white powder. Rt 0.152 (methanol/dichloromethane (5% v/v)); ¹ H NMR (300 MHz, CDCh) 5 7.88 - 7.79 (m, 2H), 7.67 (d, J= 8.7 Hz, 2H), 7.45 - 7.36 (m, 1 H), 7.33 (dd, J= 12.0, 7.7 Hz, 6H), 6.93 - 6.82 (m, 2H), 6.48 (s, 1 H), 4.40 (dd, J= 5.7, 3.8 Hz, 2H), 4.21 (dd, J= 5.9, 3.7 Hz, 2H), 3.70 (s, 2H), 3.28 (s, 3H), 2.70 (s, 3H), 2.54 (s, 3H), 2.45 (s, 3H). ¹³ C NMR (75 MHz, CDCh) 5 171 .08, 158.18, 157.51 , 154.54, 147.69, 145.04, 144.62, 144.18, 132.88, 129.92, 129.85, 129.67, 128.04, 127.51 , 127.14, 114.63, 108.25, 100.79, 68.13, 65.50, 37.79, 29.25, 24.67, 21.69, 16.87.; LRMS (+ESI) m/z: 607 ([M+Na] ⁺ , 100%), 585 (M+H] ⁺ , 63%); HPLC: 95.66% (Imax = 254 nm), RT: 96.818 min.

Intermediate D5

[0333] A solution of Intermediate B1 (40 mg, 0.104 mmol, 1 equiv.) and potassium carbonate (72 mg, 0.518 mmol, 5 equiv.) in DMF (1.7 mL) was stirred at room temperature for five minutes. To this was added a stock solution of 1 -bromo-2- fluoroethane in DMF (300 uL, 0.156 mmol, 40 uL/mL, 1 .5 equiv.) and the reaction mixture stirred at 40 °C for six days. The reaction mixture was diluted with ethyl acetate and the organic layer washed with 5% aqueous lithium chloride solution and water. The collected organics were then dried over anhydrous magnesium sulfate and concentrated in vacuo. Recrystallization from isopropyl alcohol afforded Intermediate D5 (25 mg, 56%) as off-white crystals. ¹ H NMR (300 MHz, CDCh) 5 7.77 - 7.63 (m, 2H), 7.44 - 7.34 (m, 2H), 7.33 - 7.24 (m, 3H), 7.06 - 6.98 (m, 2H), 6.48 (d, J = 1 .0 Hz, 1 H), 4.92 - 4.64 (m, 2H), 4.37 - 4.18 (m, 2H), 3.72 (s, 2H), 3.28 (s, 3H), 2.70 (d, J = 0.9 Hz, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.20, 158.75, 157.56, 154.76, 147.83, 144.74, 144.36, 130.40, 130.04, 129.73, 127.64, 127.18, 114.85, 108.31 , 100.95, 83.19, 80.92, 67.48, 67.21 , 37.91 , 29.38, 24.77, 16.97; ¹⁹ F NMR (471 MHz, CDCh) 5 -223.89; LRMS (+ESI) m/z: 433 ([M+H] ⁺ , 93%), 455 ([M+Na] ⁺ , 100%); HPLC: 96.7% (Xmax = 254 nm), RT: 24.00 min

Intermediate C1

[0334] Intermediate A1 (269 mg, 1 .54 mmol, 1 equiv.) and hydrazine monohydrate (370 pL, 7.68 mmol, 5 equiv.) were dissolved in absolute ethanol (3 mL) and heated at 80 ^s C for 4 hours. After cooling to ambient temperature, acetylacetone (190 uL, 1 .85 mmol, 1 .2 equiv.) was added followed by glacial acetic acid (3 drops). A yellow precipitate formed instantly. The reaction mixture was heated at 80 ^s C for a further 3 hours, by which time full consumption of the limiting reagent could be confirmed by thin- layer chromatography analysis. The reaction mixture was cooled to 0 ^s C and the solid that formed was isolated by vacuum filtration, washed sequentially with ice cold absolute ethanol (2 x 2.5 mL) and hexane (1 x 5 mL), and dried under high vacuum to afford Intermediate C1 (276 mg, 71%) as a colourless crystalline solid. ¹ H NMR (300 MHz, CDCh) 5 8.01 - 7.87 (m, 2H), 7.04 - 6.92 (m, 2H), 6.76 (s, 1 H), 6.50 (d, J = 1 .1 Hz, 1 H), 3.86 (s, 3H), 2.76 (d, J = 0.9 Hz, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 160.32, 158.31 , 155.63, 149.87, 145.23, 127.96, 126.08, 114.25, 108.15, 92.03, 55.46, 24.71 , 17.19; LRMS (+ESI) m/z: 254 ([M+H] ⁺ , 100%), 276 ([M+Na] ⁺ , 18%), 292 ([M+K] ⁺ , 18%). General Procedures towards amide formation

General Procedure A: NEts, PyBOP amide coupling

[0335] Intermediate A4 (100 mg, 0.3 mmol, 1 eq) was dissolved in DMF (1 mL) and secondary amine (0.4 mmol, 1.1 eq), NEts (0.06 mL, 0.4 mmol, 1 .1 eq) and PyBOP (0.18 g, 0.4 mmol, 1.1 eq) was added. This was left stirring at room temperature until reaction was complete.

General Procedure B: EEDQ amide coupling

[0336] Intermediate A4 (1 .00 equiv.) was dissolved in tetrahydrofuran. To this EEDQ (1 .20 equiv.), triethylamine (1 .50 equiv.) and desired secondary amine/aniline (1.10 equiv.) was added. The mixture was left to reflux for 12 hrs. After dilution with water the product was then extracted with dichloromethane and washed with water and brine. The organic layer was dried with magnesium sulfate and filtered, and the solvent was removed in vacuo to yield the resulting crude as a solid which was purified by flash column chromatography on silica gel.

General Procedure C: Acid chloride formation

[0337] To a solution of Intermediate A4 (1 .0 equiv.) in anhydrous dichloromethane (5 mL) was added oxalyl chloride (1 .5 equiv.) dropwise at 0 °C followed by 3 drops of catalytic N,N-dimethylformamide. The mixture was stirred for 30 min before warmed to ambient temperature and stirred for two hours. Solvent was removed first under a stream of nitrogen then the product concentrated in vacuo. No further purification was necessary to submit the resulting yellow-brown solid to the next respective amide couplings.

General Procedure D: DIPEA, DMAP amide coupling onto acid chloride

[0338] To a solution of the amine starting material (1 .2 equiv.), N,N- diisopropylethylamine (141 uL, 0.81 mmol, 3 equiv.) and catalytic 4- (dimethylamino)pyridine (6.6 mg, 0.054 mmol, 0.2 equiv.) in anhydrous dichloromethane (2 mL) was added a solution of the previously synthesised acid chloride (85 mg, 0.273 mmol, 1.0 equiv.) in dichloromethane (2.5 mL). The reaction was stirred at ambient temperature overnight and the resulting crude was purified by flash column chromatography on silica gel. General Procedure E: 2-chloro-1 -methylpyridinium iodide amide coupling

[0339] To a suspension of GS04 (1 equiv.) and 2-chloro-1 -methylpyridinium iodide (1 .5 equiv.) in anhydrous tetrahydrofuran was added triethylamine (3 equiv.). The resulting orange suspension was stirred at ambient temperature for 30 minutes. The respective amine (1.5 equiv.) was then added, the reaction stirred at ambient temperature overnight, and the resulting crude was purified by flash column chromatography on silica gel.

General Procedure F: Propylphoshonic anhydride (T3P) amide coupling

[0340] To a solution of GS04 (1 equiv.) in ethyl acetate (5 mL) was added pyridine (3 equiv.) at 0 ^S C followed by the respective amine (1.1 equiv.) and the mixture was stirred for 20 min. A solution of propylphoshonic anhydride (2.5 equiv.) was then added at 0 ^S C and the reaction mixture was allowed to warm to ambient temperature and stirred for 16 h. Upon completion of the reaction by TLC, the reaction mixture was diluted with ethyl acetate and washed with water and brine. The organic layers were dried over magnesium sulfate and concentrated in vacuo to yield the crude product, which was purified by flash column chromatography on silica gel.

Compound synthesis

Compound 1

[0341] Compound 1 was prepared according to General Procedure A with N- methylaniline (0.043 mL, 0.4 mmol, 1.1 eq). After 4 hours, DCM (20 mL) and ammonium chloride (30 mL) were added, the layers separated, and the aqueous layer extracted with DCM (3 x 10 mL). The combined organic layers were dried over anhydrous magnesium sulfate, filtered and the solvent was removed under vacuum. The product was purified via silica gel flash chromatography (ethyl acetate). Product was recrystallised from ethyl acetate/hexane to yield a white solid (0.037 g, 0.09 mmol, 31%). mp 158.8-162.0 °C; ¹ H NMR (500 MHz, CDCh) 5 7.68 (d, J = 8.6 Hz, 2H), 7.41 - 7.36 (m, 2H), 7.34 - 7.27 (m, 3H), 7.02 - 6.96 (m, 2H), 6.49 (s, 1 H), 3.87 (s, 3H), 3.73 (s, 2H), 3.28 (s, 3H), 2.72 (s, 3H), 2.56 (s, 3H); ¹³ C NMR (126 MHz, CDCh) 5 170.91 , 159.91 , 157.37, 144.16, 131.58, 130.63, 129.83, 129.64, 127.54, 126.72, 126.17, 115.40, 114.01 , 108.02, 100.77, 55.36, 37.78, 29.35, 24.23, 16.98; IR (vmax, cm’ ¹ ) 3636.52, 2836.45, 1642.51 , 1245.05, 835.29, 699.66, 556.32; LRMS (+ESI) 401.23 (51%, [M+H] ⁺ ), 423.2 (86%, [M+Na] ⁺ ); HPLC RT = 23.89 min (97.0% purity).

Compound 2

[0342] A solution of Intermediate B1 (40 mg, 0.104 mmol, 1 equiv.) and potassium carbonate (72 mg, 0.518 mmol, 5 equiv.) in N,N-dimethylformamide (1.7 mL) was stirred at room temperature for five minutes. To this was added a stock solution of alkyl bromide in N,N-dimethylformamide (300 uL, 0.156 mmol, 40 uL/mL, 1 .5 equiv.) and the reaction mixture stirred at 40 °C for six days. The reaction mixture was diluted with ethyl acetate and the organic layer washed with 5% aqueous lithium chloride solution and water. The collected organics were then dried over anhydrous magnesium sulfate and concentrated in vacuo. Recrystallization from isopropyl alcohol afforded Compound 2 (25 mg, 56%) as off-white crystals. ¹ H NMR (300 MHz, CDCh) 5 7.77 - 7.63 (m, 2H), 7.44 - 7.34 (m, 2H), 7.33 - 7.24 (m, 3H), 7.06 - 6.98 (m, 2H), 6.48 (d, J = 1 .0 Hz, 1 H), 4.92 - 4.64 (m, 2H), 4.37 - 4.18 (m, 2H), 3.72 (s, 2H), 3.28 (s, 3H), 2.70 (d, J = 0.9 Hz, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.20, 158.75, 157.56, 154.76, 147.83, 144.74, 144.36, 130.40, 130.04, 129.73, 127.64, 127.18, 114.85, 108.31 , 100.95, 83.19, 80.92, 67.48, 67.21 , 37.91 , 29.38, 24.77, 16.97; ¹⁹ F NMR (471 MHz, CDCh) 5 -223.89; LRMS (+ESI) m/z: 433 ([M+H] ⁺ , 93%), 455 ([M+Na] ⁺ , 100%); HPLC: 96.7% (Xmax = 254 nm), RT: 24.00 min.

Compound 3

[0343] Compound 3 was prepared according to General Procedure A with N- ethylaniline (0.05 mL, 0.4 mmol, 1.1 eq). After 5 hours, DCM (20 mL) and ammonium chloride (30 mL) were added, the layers separated, and the aqueous layer extracted with DCM (3 x 10 mL). The combined organic layers were dried over anhydrous MgSO4, filtered and the solvent was removed under vacuum. The product was purified via silica gel flash chromatography (ethyl acetate) to yield a brown solid (0.032 g, 0.08 mmol, 26 %). mp 137.9-145.6 °C; ¹ H NMR (500 MHz, CDCh) 5 7.68 (d, J = 8.8 Hz, 1 H), 7.40 - 7.33 (m, 2H), 7.32 - 7.23 (m, 3H), 6.99 (d, J = 8.8 Hz, 2H), 6.47 (s, 1 H), 3.87 (s, 3H), 3.75 (q, J = 7.1 Hz, 2H), 3.66 (s, 3H), 2.71 (s, 3H), 2.53 (s, 3H), 1 .10 (t, J = 7.1 Hz, 3H); ¹³ C NMR (126 MHz, CDCh) 5 170.58, 159.93, 157.49, 154.92, 147.83, 144.75, 142.72, 129.97, 129.63, 128.70, 127.74, 126.56, 114.10, 108.23, 101.07, 55.51 , 44.61 , 29.78, 24.77, 17.03, 13.22; IR (vmax, cm’ ¹ ) 2968.78, 1643.70, 1439.55, 1401.77, 1247.80, 1182.01 , 1026.30, 837.60, 699.62, 558.76; LRMS (+ESI) 415.25 (53 %, [M+H] ⁺ ) 437.21 (96 %, [M+Na] ⁺ ); HPLC RT = 25.32 min (96.0% purity).

Compound 4

[0344] Compound 4 was prepared according to General Procedure B using GS04 (73 mg, 0.234 mmol, 1 .00 equiv.) as the starting material acid and 4-methoxy-N- methylaniline (29 mg, 0.258 mmol, 1.10 equiv.) as the amine. The resulting crude was purified using silica gel flash chromatography (0 - 5% methanol/dichloromethane) to yield the desired product as light colourless crystals (0.022 g, 0.0511 mmol, 54 %). mp 321 .14 °C; ¹ H NMR (300 MHz, CDCh) 5 7.69 (d, 2H), 6.99 (d, 2H), 6.88 (d, 2H), 6.48 (s, 1 H), 3.87 (s, 3H), 3.80 (s, 3H), 3.69 (s, 2H), 3.25 (s, 3H), 2.71 (s, 3H), 2.54 (s, 3H); ¹³ C NMR (500 MHz, CDCh) 5 171.55, 159.92, 158.90, 157.49, 154.94, 152.97, 147.87, 144.75, 137.22, 129.97, 128.72, 126.56, 114.89, 114.11 , 108.24, 101.03, 55.61 , 55.50, 38.05, 29.31 , 24.81 , 17.03; LRMS (+ESI) 431 .22 [M+H] ⁺ , 883.35 [2M+Na] ⁺ ; HRMS (+ESI) calc, for C25H26N4O3 [M+Na] ⁺ : 453.4978, found: 453.1898; HPLC RT = 24.22 min (99% purity).

Compound 5

A solution of 3-methoxy-N-methylaniline (48.0 mg, 0.35 mmol, 1 .10 equiv.) and triethylamine (0.49 mL, 0.48 mmol, 1 .50 equiv.) in anhydrous dichloromethane (5 mL) was cooled to 0 °C and a solution of the acid chloride (0.100 g, 0.32 mmol, 1 .00 equiv.) previously synthesised according to General Procedure C in dichloromethane was added. After work-up, the resulting crude solid was purified via silica gel flash chromatography (2-5% methanol in chloroform (v/v)) to yield Compound 5 as a white solid (13.0 mg, 0.030 mmol, 9.4%). mp 318.25 °C; ¹ H NMR (400 MHz, CDCh) 5 7.70 (d, J = 8.3 Hz, 2H), 7.23 (d, J = 8/0 Hz, 2H), 6.99 (d, J = 8.3 Hz, 2H), 6.91 - 6.72 (m, 3H), 6.46 (s, 1 H), 3.86 (s, 3H), 3.79 (s, 3H), 3.77 (s, 2H), 3.25 (s, 3H), 2.70 (s, 3H), 2.52 (s, 3H); ¹³ C NMR (400 MHz, CDCh) 5 171.21 , 160.53, 159.93, 157.46, 154.89, 147.79, 145.45, 144.69, 130.29, 129.93, 126.48, 119.70, 114.10, 113.24, 108.22, 100.87, 55.45, 37.82, 29.44, 24.73, 16.95; LRMS (+ESI) m/z: 431.21 [M+H] ⁺ , 453.19 [M+Na] ⁺ , 883.34 [2M+Na] ⁺ ; HRMS (+ESI) calc, for C25H26N4O3 [M+Na] ⁺ : 453.4978, found: 453.1898; HPLC RT = 24.46 min (97% purity).

Compound 6

Intermediate A4 (0.050 g, 0.161 mmol, 1.00 equiv), N-methylcyclohexylamine (0.026 mL, 0.193 mmol, 1.20 equiv.) and N-methylimidazole (0.045 mL, 0.564 mmol, 3.50 equiv.) were stirred in acetonitrile at RT under nitrogen stream for half an hour. To this TCFH (0.054 g, 0.193 mmol, 1 .20 equiv.) was added and left to stir for 12 hrs. The solvent was removed in vacuo and the resulting crude solid was purified via silica gel flash chromatography (2-5 % methanol in chloroform (v/v)) to yield Compound 6 as a white solid (0.130 g, 64 %). mp 516.05 °C; ¹ H NMR (400 MHz, CDCh) 5 7.79 (d, J = 8.7 Hz, 2H), 6.98 (d, J = 8.8 Hz, 2H), 6.50 (s, 1 H), 5.30 (s, 1 H), 3.90 (s, 2H), 3.85 (s, 3H), 2.98 (s, 3H), 2.74 (s, 3H), 2.54 (s, 3H), 1 .93 - 0.64 (m, 5H); ¹³ C NMR (400 MHz, Acetone-d) 5 170.71 , 160.85, 158.11 , 155.81 , 145.72, 130.56, 127.56, 114.56, 108.86, 56.79, 55.60, 53.41 , 31.50, 27.50, 26.58, 26.36, 26.29, 26.07, 24.56, 16.66; LRMS (+ESI) m/z: 407.24 ([M+H] ⁺ ), 429.11 ([M+Na] ⁺ ), 835.42 (2M+Na] ⁺ ). HRMS (+ESI) calc, for C24H30N4O2 [M+Na] ⁺ : 429.2267, found: 429.2262; HPLC RT = 25.98 min (99% purity).

Compound 7

[0345] Compound 7 was synthesised from /V-methyl-m-toluidine (41 uL, 0.328 mmol, 1 .2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (75% v/v) followed by recrystallization from ethanol afforded the desired product (57.1 mg, 51%) as off-white crystals. Rt 0.25 (neat ethyl acetate); IR (vmax/cirr ¹ ) 1649, 1613, 1580, 1561 , 1481 , 1438, 1380, 1247, 1178, 1107, 1028, 839, 800, 711 , 638, 625, 600, 519, 449, 417; ¹ H NMR (300 MHz, CDCh) 6 7.74 - 7.65 (m, 2H), 7.30 - 7.18 (m, 1 H), 7.08 (d, J = 9.9 Hz, 3H), 7.04 - 6.94 (m, 2H), 6.47 (d, J = 1 .3 Hz, 1 H), 3.87 (s, 3H), 3.73 (s, 2H), 3.25 (s, 3H), 2.71 (d, J = 1 .1 Hz, 3H), 2.54 (d, J = 1 .7 Hz, 3H), 2.35 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.2, 159.9, 157.5, 154.9, 147.8, 144.7, 144.3, 139.7, 129.9, 129.5, 128.4, 128.2, 126.5, 124.5, 114.1 , 108.2, 100.9, 55.5, 37.9, 29.4, 24.8, 21.4, 17.0; LRMS (+ESI) m/z: 415 ([M+H] ⁺ , 67%), 437 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C25H26N4O2 [M+Na] ⁺ : 437.19535, found: 437.19480; HPLC: 97.4% (Xmax = 254 nm), RT: 25.46 min

Compound 8

[0346] Compound 8 was synthesised from A/-methyl-p-toluidine (41 uL, 0.328 mmol, 1 .2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (75% v/v) followed by recrystallization from ethanol afforded the desired product (61 .9 mg, 55%) as off-white crystals. Rt 0.25 (neat ethyl acetate); IR (vmax/crrr ¹ ) 1649, 1611 , 1563, 1509, 1482, 1438, 1376, 1282, 1244, 1173, 1106, 1024, 829, 725, 633, 602, 562, 522; ¹ H NMR (300 MHz, CDCh) 5 7.69 (d, J = 8.6 Hz, 2H), 7.18 (s, 4H), 7.04 - 6.94 (m, 2H), 6.47 (s, 1 H), 3.87 (s, 3H), 3.71 (s, 2H), 3.26 (s, 3H), 2.71 (s, 3H), 2.54 (s, 3H), 2.34 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.3, 159.9, 157.5, 144.7, 141.8, 137.6, 130.4, 129.9, 127.4, 126.6, 114.1 , 108.2, 101.0, 55.5, 37.9, 29.3, 24.8, 21.2, 17.0; LRMS (+ESI) m/z: 415 ([M+H] ⁺ , 68%), 437 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C25H26N4O2 [M+Na] ⁺ : 437.19535, found: 437.19480; HPLC: 99.1% (Xmax = 254 nm), RT: 25.64 min.

Compound 9

[0347] A solution of N-ethyl-2-(2-(4-isopropoxyphenyl)-5,7-dimethylpyrazolo[1 ,5- a]pyrimidin-3-yl)-N-phenylacetamide (60 mg, 0.136 mmol, 1 equiv.) in dichloromethane (5 mL) was cooled to 0 ^s C and to this added aluminium chloride (54 mg, 0.407 mmol, 3 equiv.). Mixture was allowed to warm to room temperature and stirred overnight.

Another portion of aluminium chloride (54 mg, 0.407 mmol, 3 equiv.) was added at room temperature and stirred for 45 minutes. The reaction was then quenched with half saturated ammonium chloride then extracted with dichloromethane. The resulting crude was purified by flash column chromatography on silica gel using methanol/dichloromethane (0-5% v/v) to afford the phenol intermediate. To a solution of this in DMF was added potassium carbonate (94 mg, 0.680 mmol, 5 equiv.) followed by 1 -bromo-2-fluoroethane (15 uL, 0.204 mmol, 1.5 equiv.). The reaction mixture was heated to 40 °C and stirred overnight. The resulting crude was diluted with ethyl acetate and washed with water and brine before being dried over magnesium sulfate concentrated in vacuo. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (50-100% v/v) followed by recrystallisation from isopropanol afforded Compound 9 (45 mg, 74%) as a white solid. ¹ H NMR (300 MHz, CDCh) 5 7.70 (d, J = 8.7 Hz, 1 H), 7.43 - 7.33 (m, 2H), 7.31 - 7.23 (m, 3H), 7.02 (d, J = 8.7 Hz, 2H), 6.47 (s, 1 H), 4.94 - 4.63 (m, 2H), 4.35 - 4.19 (m, 2H), 3.75 (q, J = 7.1 Hz, 2H), 3.66 (s, 2H), 2.70 (s, 3H), 2.53 (s, 3H), 1 .10 (t, J = 7.1 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 5 170.53, 158.72, 157.52, 154.72, 147.82, 144.72, 142.69, 130.04, 129.63, 128.67, 127.75, 127.21 , 114.81 , 108.28, 101.11 , 82.07 (d, J = 170.7 Hz), 67.34 (d, J = 20.4 Hz), 44.59, 29.75, 24.75, 16.99, 13.20; ¹⁹ F NMR (471 MHz, CDCh) 5 -223.89; LRMS (+ESI) m/z: 447 ([M+H] ⁺ , 82%), 469 ([M+Na] ⁺ , 100%); HPLC: 96.7% (Xmax = 254 nm), RT: 24.52 min.

Compound 10

[0348] Compound 10 was synthesised from N-methylcubanamine hydrochloride (33 mg, 0.195 mmol, 1.1 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (30-60% v/v) then methanol/dichloromethane (0-5% v/v) followed by trituration from ethyl acetate/hexane afforded the desired product (57 mg, 76%) as a foamy white solid. ¹ H NMR (300 MHz, CDCh) 5 7.79 - 7.65 (m, 2H), 7.05 - 6.92 (m, 2H), 6.49 (s, 1 H), 4.31 (d, 3H), 3.88 (d, 9H), 3.06 (d, 3H), 2.73 (s, 3H), 2.53 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 159.94, 157.62, 144.80, 130.10, 126.55, 1 14.14, 108.30, 55.47, 53.46, 52.41 , 47.48, 42.72, 41.67, 29.83, 29.46, 24.81 , 17.04, 1.16; LRMS (+ESI) m/z: 427 ([M+H] ⁺ , 32%), 449 ([M+Na] ⁺ , 100%); HPLC: 96.7% (Xmax = 254 nm), RT: 27.37 min.

Compound 11

[0349] Compound 11 was synthesised from 4-(methylamino)pyridine (35 mg, 0.328 mmol, 1.2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (5% v/v) followed by recrystallization from isopropanol and hexane afforded the desired product (8.6 mg, 8%) as light orange crystals. Rt 0.25 (9:1 , ethyl acetate, hexane); IR (vmax/crn- ¹ ) 1668, 1606, 1580, 1478, 1438, 1355, 1293, 1244, 1 170, 11 10, 1085, 1024, 823, 761 , 617, 506; ¹ H NMR (300 MHz, CDCh) 5 8.57 - 8.51 (m, 2H), 7.73 - 7.64 (m, 2H), 7.23 (d, J = 5.2 Hz, 2H), 7.04 - 6.95 (m, 2H), 6.50 (s, 1 H), 3.89 (d, J = 14.1 Hz, 5H), 3.29 (s, 3H), 2.71 (s, 3H), 2.55 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 6 171.1 , 160.1 ,

157.9, 154.9, 151.6, 151.0, 147.5, 144.9, 129.9, 126.1 , 114.2, 108.5, 100.0, 55.5, 37.3,

29.9, 29.8, 24.8, 16.9; LRMS (+ESI) m/z: 402 ([M+H] ⁺ , 61%), 424 ([M+Na] ⁺ , 100%);

HRMS (+ESI) m/z: Calc, for C23H23N5O2 [M+Na] ⁺ : 424.17495, found: 424.17440; HPLC: 97.5% (Xmax = 254 nm), RT : 16.73 min.

Compound 12

[0350] Compound 12 was synthesised from 3-(methylamino)benzonitrile hydrochloride (52 mg, 0.309 mmol, 1 .2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (30-80% v/v) followed by recrystallisation from toluene afforded the desired product (53 mg, 49%) as a white solid. ¹ H NMR (300 MHz, CDCh) 5 7.76 - 7.69 (m, 2H), 7.61 (t, J = 1 .9 Hz, 1 H), 7.51 - 7.36 (m, 3H), 7.05 - 6.97 (m, 2H), 6.50 (d, J = 1 .3 Hz, 1 H), 3.87 (s, 3H), 3.79 (s, 2H), 3.24 (s, 3H), 2.71 (s, 3H), 2.56 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.11 , 160.13, 157.86, 154.99, 147.43, 145.14, 144.93, 131.95, 131.12, 130.64, 130.41 , 129.97, 126.02, 117.90, 114.21 , 113.60, 108.45, 100.10, 55.49, 38.01 , 29.74, 24.79, 16.97; LRMS (+ESI) m/z: 426 ([M+H] ⁺ , 100%), 448 ([M+Na] ⁺ , 80%); HPLC: 97.5% (Xmax = 254 nm), RT: 28.91 min.

Compound 13 [0351] Compound 13 was synthesised from 3-chloro-N-methylaniline hydrochloride (55 mg, 0.309 mmol, 1.2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (20-70% v/v) followed by recrystallisation from toluene afforded the desired product (63 mg, 57%) as a white solid. ¹ H NMR (300 MHz, CDCh) 5 7.77 - 7.66 (m, 2H), 7.30 - 7.16 (m, 4H), 7.06 - 6.96 (m, 2H), 6.52 - 6.44 (m, 1 H), 3.87 (s, 3H), 3.78 (s, 2H), 3.23 (s, 3H), 2.75 - 2.68 (m, 3H), 2.55 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.14, 160.02, 157.66, 154.94, 147.65, 145.45, 144.80, 134.95, 130.49, 129.96, 127.93, 127.70, 126.26, 125.77, 114.16, 108.33, 100.51 , 55.48, 37.93, 29.56, 24.78, 16.99; LRMS (+ESI) m/z: 435 ([M+H] ⁺ , 100%), 457 ([M+Na] ⁺ , 63%); HPLC: 99% (Xmax = 254 nm), RT: 32.38 min.

Compound 14

[0352] Synthesised from A/-methylisoquinolin-7-amine (67.4 mg, 0.426 mmol, 1 .2 equiv.) following General Procedure D using the acid chloride formed from General Procedure C. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (0.5-3% v/v) afforded Compound 14 (7 mg, 5%) as an off-white powder. Rt 0.176 (ethyl acetate/hexane (20% v/v)); ¹ H NMR (300 MHz, Chloroform-d) 5 9.20 (s, 1 H), 8.53 (d, J= 5.7 Hz, 1 H), 7.84 (d, J= 2.1 Hz, 1 H), 7.77 - 7.65 (m, 2H), 7.60 (d, J= 5.6 Hz, 2H), 7.52 - 7.42 (m, 2H), 7.05 - 6.93 (m, 2H), 3.87 (s, 3H), 3.31 (s, 3H), 2.98 (s, 2H), 2.66 (s, 3H), 2.42 (s, 3H). ¹³ C NMR (75 MHz, Chloroform-d) 5 171.26, 159.94, 157.47, 154.71 , 150.63, 144.56, 143.54, 131.44, 130.89, 129.78, 129.33, 114.03, 108.14, 100.27, 55.36, 37.94, 24.52, 16.77; LRMS (+ESI) m/z: 474 ([M+Na] ⁺ , 100%), 452 ([M+H] ⁺ , 14%).

Comparator X

[0353] Comparator X was synthesised from N-methyladamantylamine hydrochloride (72 mg, 0.356 mmol, 1.2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (10-40% v/v) afforded the Comparator X (86 mg, 63%) as a white solid. ¹ H NMR (300 MHz, CDCh) 5 7.74 - 7.66 (m, 2H), 7.02 - 6.94 (m, 2H), 6.48 (d, J = 1 .1 Hz, 1 H), 3.88 (s, 2H), 3.85 (s, 3H), 2.97 (s, 3H), 2.73 (s, 3H), 2.54 (s, 3H), 2.12 (dd, J = 34.3, 4.4 Hz, 9H), 1.79 - 1 .63 (m, 6H); ¹³ C NMR (75 MHz, CDCh) 5 171.53, 159.89, 157.55, 154.94, 147.86, 144.86, 129.94, 126.61 , 114.09, 108.25, 101 .51 , 58.41 , 55.49, 39.58, 36.64, 32.29, 31.18, 30.26, 24.76, 17.05; LRMS (+ESI) m/z: 459 ([M+H] ⁺ , 100%), 481 ([M+Na] ⁺ , 79%); HPLC: 98.7% (Xmax = 254 nm), RT: 29.87 min.

[0354] Compound 15

[0355] To a solution of N-methylpyridin-3-amine (62 uL, 0.609 mmol, 1 .2 equiv.) in tetrahydrofuran (3 mL) cooled to 0 °C was added sodium hydride in mineral oil (60% w/w, 24.3 mg, 0.609 mmol, 2.5 equiv.) and the mixture stirred for 30 min. To this was added a solution of the acid chloride (158 mg, 0.507 mmol, 1 equiv.) previously synthesised according to General Procedure C in anhydrous dichloromethane (3.5 mL) and tetrahydrofuran (2 mL) and the reaction stirred at ambient temperature overnight. The reaction mixture was quenched with water (1 mL) and extracted with dichloromethane (1 x 20 mL). The collected organics were washed with sodium hydroxide solution (3 M, 3 x 20 mL) and brine (1 x 20 mL) and then dried over anhydrous magnesium sulfate and concentrated in vacuo. Purification by flash chromatography on silica gel using methanol/dichloromethane (10% v/v) followed by recrystallization from isopropanol/hexane afforded Compound 15 (60.1 mg, 30%) as orange crystals. Rt 0.30 (10% v/v methanol in dichloromethane); IR (vmax/cm ^-1 ) 1643, 1558, 1423, 1279, 1200, 1182, 1024, 834, 715, 639, 600, 524; ¹ H NMR (300 MHz, CDCh) 5 8.60 (d, J = 2.5 Hz, 1 H), 8.50 (d, J = 4.8 Hz, 1 H), 7.68 (dd, J = 16.6, 8.4 Hz, 3H), 7.30 (dd, J = 8.1 , 4.8 Hz, 1 H), 7.06 - 6.95 (m, 2H), 6.49 (s, 1 H), 3.86 (s, 3H), 3.72 (s, 2H), 3.29 (s, 3H), 2.71 (s, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.2, 159.9, 157.6, 154.9, 147.7, 144.2, 139.7, 129.9, 128.3, 128.2, 126.6, 124.5, 114.2, 108.7, 100.1 , 55.4, 37.5, 29.9, 24.7, 16.9; LRMS (+ESI) m/z: 402 ([M+H] ⁺ , 31%), 424 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C23H23N5O2 [M+Na] ⁺ : 424.17495, found: 424.17440; HPLC: 98.7% (Xmax = 254 nm), RT: 10.28 min.

Compound 16

[0356] A solution of Intermediate C1 (50 mg, 0.197 mmol, 1 equiv.) in dichloromethane (3 mL) was cooled to 0 ^s C. Oxalyl chloride (70 uL, 0.790 mmol, 4 equiv.) was added, followed by DIPEA (40 uL, 0.217 mmol, 1.1 equiv.). The reaction mixture was allowed to warm to ambient temperature, stirred for 90 minutes, and subsequently concentrated under a gentle flow of nitrogen gas. The dark brown residue that remained was redissolved in THF (3 mL) and added to a separate flask containing diethylamine (62 uL, 0.591 mmol, 3 equiv.), pyridine (80 uL, 0.985 mmol, 5 equiv.), and THF (3 mL). After 2 hours stirring at ambient temperature, the reaction mixture was concentrated under reduced pressure and the crude product purified, first by flash column chromatography (60-70% ethyl acetate in hexane) and subsequently by recrystallisation from isopropanol (2 mL), to afford Compound 16 (33 mg, 43%) as a colourless crystalline solid. ¹ H NMR (300 MHz, CDCh) 5 7.98 (d, J= 8.8 Hz, 2H), 6.99 (d, J= 8.8 Hz, 2H), 6.75 (s, 1 H), 3.87 (s, 3H), 3.56 (q, J= 7.1 Hz, 2H), 3.32 (q, J= 7.1 Hz, 2H), 2.79 (s, 3H), 2.58 (s, 3H), 1.35 (t, J= 7.1 Hz, 3H), 1.16 (t, J = 7.1 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 6 185.31 , 168.33, 162.54, 161.05, 158.49, 150.57, 146.29, 131 .34, 124.49, 113.73, 11 1 .09, 104.41 , 55.50, 42.20, 38.70, 24.94, 17.24, 13.83, 12.67; LRMS (+ESI) m/z: 381 ([M+H] ⁺ , 48%), 403 ([M+Na] ⁺ , 100%); HPLC 98.76% (Xmax = 254 nm), RT : 23.37 min.

Compound 17

[0357] A solution of Intermediate C1 (80 mg, 0.316 mmol, 1 equiv.) in dichloromethane (5 mL) was cooled to 0 ^s C. Oxalyl chloride (135 uL, 1.579 mmol, 5 equiv.) was added, followed by DIPEA (60 uL, 0.347 mmol, 1.1 equiv.). The reaction mixture was allowed to warm to ambient temperature, stirred for 90 minutes, and subsequently concentrated under a gentle flow of nitrogen gas. The dark brown residue that remained was redissolved in THF (5 mL) and added to a separate flask containing N-methylaniline (103 uL, 0.948 mmol, 3 equiv.), pyridine (130 uL, 1 .580 mmol, 5 equiv.), and THF (5 mL). After 2 hours stirring at ambient temperature, the reaction mixture was concentrated under reduced pressure and the crude product purified, first by flash column chromatography (60-70% ethyl acetate in hexane) and subsequently by recrystallisation from isopropanol (4 mL), to afford Compound 17 (55 mg, 42%) as a colourless crystalline solid. ¹ H NMR (300 MHz, CDCh) 5 8.12 - 7.76 (m, 2H), 7.62 - 7.15 (m, 5H), 7.05 - 6.88 (m, 2H), 6.82 - 6.74 (m, 1 H), 3.86 (d, J = 15.3 Hz, 3H), 3.44 (d, J = 41 .4 Hz, 3H), 2.79 (dd, J = 18.6, 0.9 Hz, 3H), 2.66 (d, J = 21 .9 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 5 184.26, 167.85, 163.32, 160.86, 156.85, 149.66, 147.25, 142.26, 131.22, 129.21 , 127.65, 126.48, 124.28, 113.84, 1 12.13, 103.44, 55.72, 35.94, 25.29, 16.97; LRMS (+ESI) m/z: 415 ([M+H] ⁺ , 30%), 437 ([M+Na] ⁺ , 100%); HPLC 99.75% (Xmax = 254 nm), RT : 29.38 min.

Compound 18

[0358] Compound 18 was synthesised from 4-chloro-N-methylaniline hydrochloride (55 mg, 0.309 mmol, 1.2 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (20-70% v/v) followed by recrystallisation from toluene afforded Compound 18 (45 mg, 41%) as a white solid. ¹ H NMR (300 MHz, CDCh) 5 7.77 - 7.64 (m, 2H), 7.36 - 7.27 (m, 2H), 7.23 - 7.15 (m, 2H), 7.05 - 6.95 (m, 2H), 6.53 - 6.43 (m, 1 H), 3.87 (s, 3H), 3.74 (s, 2H), 3.23 (s, 3H), 2.76 - 2.67 (m, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.18, 160.00, 157.62, 154.92, 147.66, 144.79, 142.84, 129.95, 129.80, 128.88, 126.32, 114.14, 108.36, 100.56, 55.48, 37.95, 29.59, 24.78, 17.69, 16.98; LRMS (+ESI) m/z: 435 ([M+H] ⁺ , 14%), 457 ([M+Na] ⁺ , 100%) ; HPLC: 97.28% (Xmax = 254 nm), RT : 26.51 min

Compound 19

[0359] To a solution of 4-(methylamino)benzonitrile (66.9 mg, 0.506 mmol, 1 .2 equiv.), and 4-(dimethylamino)pyridine (103 mg, 0.843 mmol, 2.5 equiv.) in anhydrous dichloromethane (3 mL) was added a solution of the acid chloride (105 mg, 0.337 mmol, 1 equiv.) previously synthesised according to General Procedure C in dichloromethane (3 mL). The reaction was stirred at ambient temperature overnight. Purification by flash column chromatography on silica gel using ethyl acetate/hexane (80% v/v) followed by repeated trituration from hexane afforded Compound 19 (14.8 mg, 11%) as an off- white powder. Rt 0.22 (8:2, ethyl acetate, hexane); IR (vmax/cirr ¹ ) 2919, 1654, 1601 , 1560, 1507, 1476, 1439, 1370, 1303, 1250, 1175, 1114, 1023, 861 , 814, 759, 599, 581 ; ¹ H NMR (300 MHz, CDCh) 5 7.78 - 7.65 (m, 2H), 7.65 - 7.49 (m, 2H), 7.33 (d, J = 1 .7 Hz, 2H), 7.05 - 6.95 (m, 2H), 6.50 (s, 1 H), 3.86 (s, 3H), 3.84 (s, 2H), 3.25 (s, 3H), 2.71 (s, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.1 , 160.1 , 157.8, 154.9, 148.2, 144.9, 133.3, 129.9, 127.9, 126.0, 118.2, 114.2, 108.5, 100.1 , 77.3, 55.5, 37.9, 30.0, 24.8, 16.9; LRMS (+ESI) m/z: 426 ([M+H] ⁺ , 48%), 448 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C25H23N5O2 [M+Na] ⁺ : 448.17495, found: 448.17440; HPLC: 97.4% (Xmax = 254 nm), RT: 15.33 min.

Compound 20

[0360] Synthesised from (R)-methylbenzylamine (0.13 mL, 1 mmol, 1.1 equiv.) and 250 mg (0.8 mmol, 1 equiv.) of Intermediate A4 according to General Procedure A using according to General Procedure A. Purification of the crude product by flash column chromatography on silica gel using methanol/ethyl acetate (10% v/v) followed by recrystallisation from ethyl acetate/hexane afforded Compound 20 (240 mg, 73%) as an orange solid. IR (vmax/crn’ ¹ ) 3636.49, 3268.43, 1634.02, 1244.02, 1178.00, 823.42, 557.46, 519.14; ¹ H NMR (300 MHz, CDCh) 5 7.80 (d, J = 8.9 Hz, 2H), 7.34 (br, 1 H), 7.25 - 7.23 (m, 2H), 7.20 (m, 3H), 7.01 (d, J = 8.9 Hz, 2H), 6.63 (d, J = 1 .0 Hz, 1 H), 5.14 - 4.89 (m, 1 H), 3.86 (d, J = 3.6 Hz, 5H), 2.81 (s, 3H), 2.57 (s, 3H), 1.39 (d, J = 6.9 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 5 170.69, 160.53, 157.90, 143.45, 132.30, 130.31 , 129.44, 128.65, 127.25, 126.20, 124.81 , 115.89, 114.52, 108.40, 99.53, 55.52, 49.48, 31.89, 23.72, 22.10, 17.35; LRMS (+ESI) m/z: 415 (69 %, [M+H] ⁺ ), 437 (100 %, [M+Na] ⁺ ); HPLC 98.5% (Xmax = 254 nm), RT: 24.26 min.

Compound 21

[0361] Compound 21 was synthesised from N-methyl-3-(trifluoromethyl)aniline (56.26 liL, 0.385 mmol, 1.5 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/dichloromethane (50% v/v) followed by repeated trituration with hexane and recrystallisation from hexane/isopropanol afforded the desired product (52 mg, 43%) as pale yellow solids. Rt 0.2 (50% v/v ethyl acetate in dichloromethane); ¹ H NMR (300 MHz, CDCh) 5 7.70 (d, J = 8.5 Hz, 2H), 7.54 (s, 1 H), 7.46 (s, 3H), 7.00 (d, J = 8.5 Hz, 2H), 6.48 (s, 1 H), 3.86 (s, 3H), 3.77 (s, 2H), 3.26 (s, 3H), 2.70 (s, 3H), 2.53 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.04, 159.93, 157.58, 154.79, 147.41 , 144.74, 144.71 , 130.81 , 130.79, 130.05, 129.83, 126.03, 125.32, 124.21 , 114.03, 108.23, 100.20, 77.24, 55.33, 37.89, 29.57, 24.56, 16.81 ; ¹⁹ F NMR (282 MHz, CDCh) 5 -62.61 ; LRMS (+ESI) m/z: 469 ([M+H] ⁺ , 18%), 491 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C25H23F3N4O2 [M+Na] ⁺ : 491.16708, found: 491.16645; HPLC 96.18% (Xmax = 254 nm), RT: 23.47 min.

Compound 22

[0362] Compound 22 was synthesised from N-methyl-4-(trifluoromethyl)aniline (54.47 liL, 0.385 mmol, 1.5 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/dichloromethane (50% v/v) followed by recrystallisation from hexane/isopropanol afforded the desired product (36 mg, 30%) as a yellow crystals. Rt 0.2 (50% v/v ethyl acetate in dichloromethane); ¹ H NMR (300 MHz, CDCh) 5 7.71 (d, J = 8.4 Hz, 2H), 7.54 (d, J = 8.2 Hz, 2H), 7.34 (d, J = 8.2 Hz, 2H), 7.00 (d, J = 8.6 Hz, 2H), 6.47 (s, 1 H), 3.87 (s, 3H), 3.82 (s, 2H), 3.24 (s, 3H), 2.69 (s, 3H), 2.52 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 170.99, 159.93, 157.53, 154.73, 147.33, 147.22, 144.66, 129.77, 127.43, 126.45, 126.40, 126.03, 114.04, 108.28, 100.14, 55.35, 37.81 , 29.86, 25.37, 24.59, 16.79; ¹⁹ F NMR (282 MHz, CDCh) 5 -62.47; LRMS (+ESI) m/z: 469 ([M+H] ⁺ , 25%), 491 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C25H23F3N4O2 [M+Na] ⁺ : 491 .16708, found: 491 .16641 ; HPLC 96.20% (Xmax = 254 nm), RT: 27.193 min.

Compound 23

[0363] Compound 23 was synthesised from N-methyl-tert-butylamine (57.26 |iL, 0.478 mmol, 1 .5 equiv.) according to General Procedure C and D. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (60% v/v) followed by repeated trituration from hexane/ethyl acetate afforded the desired product (44.4 mg, 37%) as a pale yellow powder. Rt 0.25 (70% v/v ethyl acetate in hexane); ¹ H NMR (300 MHz, CDCh) 5 7.80 - 7.66 (m, 2H), 7.01 - 6.93 (m, 2H), 6.49 (d, J = 1 .1 Hz, 1 H), 3.91 (s, 2H), 3.85 (s, 3H), 2.97 (s, 3H), 2.73 (d, J = 0.9 Hz, 3H), 2.54 (s, 3H), 1.37 (s, 9H); ¹³ C NMR (75 MHz, CDCh) 5 171.66, 159.92, 157.62, 155.01 , 147.76, 144.92, 129.96, 126.56, 114.07, 108.28, 101 .39, 57.05, 55.48, 32.41 , 32.00, 28.33, 24.73, 17.06; LRMS (+ESI) m/z: 381 ([M+H] ⁺ , 27%), 403 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C22H29N4O2 [M+H] ⁺ : 381 .22905, found: 381 .22845; HPLC 95.07% (Xmax = 254 nm), RT: 23.47 min.

Compound 24

[0364] Synthesised from (S)-methylbenzylamine (0.13 mL, 0.9 mmol, 1.1 equiv.) and 250 mg (0.8 mmol, 1 equiv.) of Intermediate A4 according to General Procedure A using. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (30% v/v) followed by recrystallisation from isopropyl alcohol afforded Compound 24 (242 mg, 73%) as an orange solid. IR ( max/crn ^-1 ) 3644.24, 3269.21 , 1634.60, 1436.02, 1244.97, 1 178.79, 1047.50, 841.13, 694.46, 558.95, 519.75; ¹ H NMR (300 MHz, CDCh) 5 7.85 (d, J = 8.9 Hz, 2H), 7.34 (br, 1 H), 7.26 (m, 5H), 7.02 (d, J = 8.9 Hz, 2H), 6.66 (s, 1 H), 5.19 - 4.91 (m,1 H), 3.91 (d, J = 2.9 Hz, 2H), 3.86 (s, 3H), 2.85 (s, 3H), 2.65 (s, 3H), 1 .43 (d, J = 6.9 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 5 170.38, 160.71 , 157.64, 143.52, 132.43, 130.49, 128.65, 128.40, 127.25, 126.28, 124.44, 115.92, 114.55, 108.13, 99.68, 55.53, 49.61 , 31.70, 23.08, 22.16, 17.55; LRMS (+ESI) m/z: 415 (39 %, [M+H] ⁺ ), 437 (100 %, [M+Na] ⁺ ); HPLC 99.3% (Xmax = 254 nm), RT : 24.26 min.

Compound 25

[0365] Synthesised from aniline (145 > L, 1 .592 mmol, 5 equiv.) according to General Procedure C and D without the use of any A/,A/-diisopropylethylamine. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (40% v/v) followed by repeated trituration from hexane/dichloromethane afforded Compound 25 (107 mg, 87%) as a yellow powder. Rt 0.30 (50% v/v ethyl acetate in hexane); ¹ H NMR (300 MHz, CDCh) 6 9.28 (s, 1 H), 7.90 (dd, J = 8.8, 2.3 Hz, 2H), 7.49 (d, J = 8.0 Hz, 2H), 7.36 - 7.18 (m, 3H), 7.08 - 7.04 (m, 2H), 6.61 (s, 1 H), 3.93 (s, 2H), 3.87 (s, 3H), 2.79 (s, 3H), 2.68 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 169.96, 160.33, 158.27, 155.14, 147.59, 145.93, 138.82, 130.42, 129.02, 125.24, 123.82, 119.51 , 114.48, 108.65, 99.66, 55.49, 33.55, 24.81 , 17.08; LRMS (+ESI) m/z: 387 ([M+H] ⁺ , 41%), 409 ([M+Na] ⁺ , 100%); HRMS (+ESI) m/z: Calc, for C23H22N4O2 [M+H] ⁺ : 387.18210, found: 387.18165; HPLC 96.26% (Xmax = 254 nm), RT: 23.76 min.

Compound 26

[0366] Synthesised from indoline (43.33 mL, 0.257 mmol, 1 .5 equiv.) according to General Procedure E. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (40-60% v/v) followed by repeated trituration with hexane and recrystallisation from hexane/isopropyl alcohol afforded Compound 26 (32 mg, 30%) as an off-white powder. Rt 0.25 (80% v/v ethyl acetate in dichloromethane); ¹ H NMR (300 MHz, CDCh) 5 8.23 (d, J= 8.0 Hz, 1 H), 7.77 (d, J = 7.7 Hz, 2H), 7.17 (q, J= 7.4 Hz, 2H), 6.98 (d, J= 8.4 Hz, 4H), 4.32 (dd, J= 12.3, 5.3 Hz, 2H), 4.01 (s, 2H), 3.83 (d, J= 2.5 Hz, 3H), 3.23 (t, J= 8.6 Hz, 2H), 2.74 (d, J= 2.5 Hz, 3H), 2.52 (d, J= 2.4 Hz, 3H); ¹³ C NMR (75 MHz, CDCh) 5 169.22, 159.89, 157.75, 155.31 , 147.82, 144.88, 143.37, 131.16, 129.97, 127.52, 126.24, 124.46, 123.52, 117.27, 114.15, 108.35, 99.68, 77.24, 55.33, 48.25, 30.90, 28.24, 24.67, 16.95; LRMS (+ESI) m/z: 413 ([M+H] ⁺ , 68%), 435 ([M+Na] ⁺ , 100%); HPLC 99.70% (Xmax = 254 nm), RT: 25.99 min.

Compound 27

[0367] Synthesised from tetrahydroquinoline (48.38 mL, 0.257 mmol, 1 .5 equiv.) according to General Procedure E. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/hexane (40-60% v/v) followed by repeated trituration with hexane and recrystallisation from hexane/isopropyl alcohol afforded Compound 27 (90 mg, 82%) as an off-white powder. Rt 0.25 (80% v/v ethyl acetate in dichloromethane); ¹ H NMR (300 MHz, CDCh) 5 7.66 (d, J= 8.4 Hz, 2H), 7.45 (s, 1 H), 7.20 - 7.03 (m, 4H), 6.93 (d, J = 8.4 Hz, 2H), 6.49 (s, 1 H), 4.13 (s, 2H), 3.82 (d, J= 12.4 Hz, 6H), 2.71 (s, 6H), 2.71 (d, J= 13.4 Hz, 1 H), 2.54 (s, 3H), 1.91 (p, J = 6.6 Hz, 2H); ¹³ C NMR (75 MHz, CDCh) 5 171.01 , 159.79, 157.56, 154.66, 147.75, 144.72, 129.72, 128.36, 126.32, 126.07, 125.17, 125.11 , 114.00, 108.23, 101 .01 , 77.24, 55.35, 29.61 , 26.85, 24.62, 24.07, 16.89.; LRMS (+ESI) m/z: 427 ([M+H] ⁺ , 100%), 449 ([M+Na] ⁺ , 45%); HPLC 98.83% (Xmax = 254 nm), RT: 26.37 min.

Compound 28

[0368] Synthesised as per Intermediate D3 over 4 steps starting from methyl 4- fluorobenzoate (2.95 g, 19.14 mmol, 1 eq) with no isolation, purification, or characterisation of intermediates. Purification of the crude product by recrystallisation from isopropyl alcohol afforded Compound 28 (68 mg, 1 .75 mmol, 0.9% over 4 steps) as a colourless crystalline solid. ¹ H NMR (300 MHz, CDCh) 5 7.74 (dd, J= 8.5, 5.6 Hz, 2H), 7.46 - 7.27 (m, 5H), 7.22 - 7.09 (m, 2H), 3.70 (s, 2H), 3.28 (s, 3H), 2.71 (s, 3H), 2.55 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.10, 157.81 , 154.27, 147.84, 144.82, 144.32, 130.60, 130.49, 129.82, 127.65, 115.74, 115.45, 108.59, 37.90, 29.20, 24.83, 16.99; ¹⁹ F NMR (282 MHz, CDCh) 6 -113.69; LRMS (+ESI) m/z: 411 (39 %, [M+H] ⁺ ), 799 (50 %, [2M+Na] ⁺ ); HPLC 95.38% (Xmax = 254 nm), RT: 24.43 min.

Compound 29

[0369] Synthesised from 3-fluoro-A/-methylaniline (44.18 mg, 0.353 mmol, 1.1 equiv.) according to General Procedure F. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (3% v/v) Compound 29 (85.0 mg, 63%) as an off-white powder. Rt 0.344 (ethyl acetate/dichloromethane (50% v/v)); IR ( max/cm ^-1 ) 1649, 1605, 1558, 1524, 1480, 1440, 1379, 1281 , 1243, 1180, 1107, 1028, 840, 790, 702, 638, 599, 520; ¹ H NMR (300 MHz, CDCh) 5 7.70 (d, J = 8.4 Hz, 2H), 7.39 - 7.27 (m, 1 H), 7.07 (d, J = 8.3 Hz, 2H), 7.00 (d, J = 8.4 Hz, 3H), 6.48 (s, 1 H), 3.86 (s, 3H), 3.76 (s, 2H), 3.26 (s, 3H), 2.70 (s, 3H), 2.54 (s, 3H); ¹³ C NMR (75 MHz, CDCh) 5 171.15, 164.72, 163.07 - 153.09 (m), 147.68, 145.78 (d, J = 9.5 Hz), 144.79, 130.70 (d, J = 9.0 Hz), 129.95, 126.32, 123.32, 114.86 (dd, J = 34.4, 21 .2 Hz), 114.14, 108.31 , 100.55, 77.36, 55.46, 37.87, 29.41 , 24.71 , 16.97; ¹⁹ F NMR (282 MHz, CDCh) 5 -110.85; LRMS (+ESI) m/z: 419 ([M+H] ⁺ , 34%), 441 ([M+Na] ⁺ , 100%), 859 ([2M+Na] ⁺ , 37%); HRMS (+ESI) m/z: Calc, for C24H ₂₃ FN4NaO2 [M+Na] ⁺ : 441 .16972, found: 441 .16917; HPLC: 96.43% (Xmax = 254 nm), RT: 25.061 min.

Compound 30 [0370] Synthesised from 4-fluoro-A/-methylaniline (44.18 mg, 0.353 mmol, 1.1 equiv.) according to General Procedure F. Purification of the crude product by flash column chromatography on silica gel using ethyl acetate/dichloromethane (50-70% v/v) afforded Compound 30 (42 mg, 31 %) as an off-white powder. Rt 0.214 (ethyl acetate/dichloromethane (50% v/v)); IR (vmax/crrr ¹ ) 1647, 1605, 1561 , 1506, 1480, 1438, 1376, 1281 , 1247, 1172, 11 15, 1025, 833, 815, 603, 558, 525; ¹ H NMR (300 MHz, CDCh) 5 7.70 (d, J = 8.2 Hz, 2H), 7.26 (d, J = 12.4 Hz, 1 H), 7.10 - 6.94 (m, 5H), 6.48 (s, 1 H), 3.86 (s, 3H), 3.70 (s, 2H), 3.24 (s, 3H), 2.71 (s, 3H), 2.53 (s, 3H). ¹³ C NMR (75 MHz, CDCh) 5 171.20, 161.85 - 152.96 (m), 147.60, 144.67, 140.23 (d, J = 3.2 Hz), 129.84, 129.25 (d, J = 8.6 Hz), 126.27, 1 16.45 (d, J = 22.6 Hz), 1 14.00, 108.18, 100.56, 77.27, 55.35, 53.44, 37.91 , 29.27, 24.63, 16.86.; ¹⁹ F NMR (282 MHz, CDCh) 5 -1 13.86; LRMS (+ESI) m/z: 419 ([M+H] ⁺ , 23%), 441 ([M+Na] ⁺ , 100%), 859 ([2M+Na) ⁺ , 38%;

HRMS (+ESI) m/z: Calc, for C24H ₂₃ FN4NaO2 [M+Na] ⁺ : 441.16972, found: 441.16929; HPLC: 97.55% (Xmax = 254 nm), RT: 25.051 min.

Compound 31

[0371] Synthesised from indole (45.26 mg, 0.386 mmol, 1 .2 equiv.) using the acid chloride formed from General Procedure C. Indole was dissolved in anhydrous DMF and stirred at 0 ^S C before adding sodium hydride (16.98 mg, 0.425 mmol, 1.3 equiv.) and stirring for 10 mins at 0 ^S C followed by stirring for 1 hr at room temperature. At this point, the prepared acid chloride was redissolved in DMF (4 mL) and stirred at room temperature for 16 h. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (0.5-2% v/v) followed by recrystallisation from methanol/dichloromethane (20% v/v) afforded Compound 31 (32 mg, 25%) as an off-white powder. Rt 0.176 (ethyl acetate/hexane (20% v/v)); IR (vmax/crn ^-1 ) 1655, 1608, 1561 , 1478, 1439, 1207, 1 171 , 1022, 923, 830, 766, 741 , 701 , 618, 560; ¹ H NMR (300 MHz, CDCh) 5 7.76 (dd, J = 4.0, 1 .6 Hz, 1 H), 7.74 - 7.69 (m, 2H), 7.56 (d, J = 7.7 Hz, 1 H), 7.32 (d, J = 7.6 Hz, 1 H), 7.29 - 7.23 (m, 1 H), 6.96 (dd, J = 8.7, 1 .8 Hz, 2H), 6.64 (dd, J = 3.8, 1 .6 Hz, 1 H), 6.55 (s, 1 H), 4.54 (d, J = 1 .7 Hz, 2H), 3.82 (d, J = 1 .6 Hz, 3H), 2.77 (d, J = 1 .6 Hz, 3H), 2.53 (d, J = 1 .7 Hz, 3H). ¹³ C NMR (75 MHz, CDCh) 5 171.11 , 169.41 , 157.74, 157.51 , 154.63, 147.72, 144.67, 144.22, 129.85, 129.66, 127.52, 127.30, 125.04, 123.64, 120.73, 116.85, 114.99, 114.25, 109.06, 108.24, 108.62, 55.89, 29.19, 24.66, 16.88. LRMS (+ESI) m/z: 433 ([M+Na] ⁺ , 100%), 843 ([2M+Na] ⁺ , 13%); HRMS (+ESI) m/z: Calc, for C ₂ 5H ₂₅ N4NaO2 [M+Na] ⁺ : 433.16350, found: 433.16296; HPLC: 95.89% (Xmax = 254 nm), RT: 27.901 min.

Compound 32

[0372] Synthesised from A/-methylbenzo[d][1 ,3]dioxol-5-amine (58.23 mg, 0.385 mmol, 1.2 equiv.) following General Procedure D using the acid chloride formed from General Procedure C. Purification of the crude product by flash column chromatography on silica gel using methanol/dichloromethane (1 -3% v/v) afforded Compound 32 (6 mg, 4%) as brown powder. Rt 0.176 (ethyl acetate/hexane (20% v/v)); ¹ H NMR (300 MHz, Chloroform-d) 5 ¹ H NMR (300 MHz, CDCh) 5 7.74 - 7.65 (m, 2H), 7.05 - 6.94 (m, 2H), 6.82 - 6.73 (m, 3H), 6.48 (s, 1 H), 5.98 (s, 2H), 3.86 (s, 3H), 3.74 (s, 2H), 3.22 (s, 3H), 2.71 (s, 3H), 2.54 (s, 3H). ¹³ C NMR (75 MHz, Chloroform-d) 5 159.84, 157.48, 148.26, 145.32, 136.78, 130.03, 129.84, 128.01 , 114.00, 109.23, 108.50, 107.96, 101 .71 , 98.87, 55.35, 37.91 , 24.60, 21.66, 16.89; LRMS (+ESI) m/z: 467 ([M+Na] ⁺ , 100%), 445 ([M+H] ⁺ , 30%), 911 ([2M+Na] ⁺ , 24%).

Example 2: Radiolabelling of compounds

[0373] Intermediate B1 was radiolabelled with ¹¹ C through formation of an anisolyl group in accordance with the protocol outlined in Bioorganic and Medicinal Chemistry 2005, 13, 6188-6194. Intermediate D5 was radiolabelled with ¹⁸ F through displacement of the tosylate group in accordance with the protocol outlined in Journal of Nuclear Medicine 2008, 49, 814-822. The introduction of radiolabels is outlined in Scheme 4 below.

Scheme 4

Intermediate B1 Intermediate B1-[ ¹¹ C]

Intermediate D5 Intermediate D5-[ ^1S F]

Example 3: Radioligand Binding Assay

[0374] Binding affinities (Ki) to wild type and A147T TSPO were measured as per Sokias, R. et al. Med Chem Commun. 2017, 8(1 ), 202. Briefly, membranes were prepared from HEK293T cells stably transfected with wild type and A147T TSPO by homogenisation, using an Ultra-Turrax hand-held homogeniser. These cells have previously been validated as an in vitro model of low- and high-affinity TSPO binders. Wild type (20 pg/well) and A147T (5 pg/well) TSPO membranes were diluted in 50 mM Tris HCI (pH 7.4), and were incubated at 4 °C for 90 min with ~ Kd concentration of [ ³ H]PK11195 (10 nM; PerkinElmer) and test compounds (0.3 nM - 10 pM). A high concentration (1 pM) of unlabelled PK11195 was used to measure non-specific binding, which was less than 10% of total binding. Filtration through a 96-well glass-fibre filter plate (millipore) was used to terminate reactions. Plates were then washed 8 times with ice-cold 50 mM trisaminomethane (Tris) HCL Radioactivity was read in a Microbeta 2450 Microplate Counter (PerkinElmer) after addition of Microscint 0. Data were analysed using Graphpad Prism 6.0 (GraphPad), applying a four-parameter non-linear regression curve fit to calculate Ki values. Data are expressed as mean ± SEM from at least two independent experiments.

Table 2: Binding affinities of compounds

Without wishing to be bound by theory, it is thought that the adamantyl group of Comparator X is too bulky and therefore does not demonstrate sufficient binding affinity to TSPO. Both Compound 6 and Compound 10 feature less bulky cycloalkyl groups at the same position, in either a six-membered ring (Compound 6) or a polycyclic system (Compound 10). Despite these similarities to Comparator X, both Compound 6 and Compound 10 display binding affinity to TSPO.