PURPOSE: To prepare the titled substance useful as a remedy for ulcer in itself or in the form of an aluminum derivative and administrable without side-effect, in high yield and purity, by reacting an acetic acid derivative with urea in the presence of a condensation agent.

CONSTITUTION: The compound of formula II is prepared by reacting an acetic acid derivative of formula I (R1 is alkyl, aryl, aralkyl, or two R1 together form an alkylene group; R is H, alkyl, aryl, or aralkyl) with urea in the presence of a condensation agent at 55W85°C. The condensation agent is, e.g. mineral acid, thiohalide, inorganic alkali, alcoholate, etc., and its amount is pref. 0.5W2.0 equivalent per 1 equivalent of the compound of formula I. The reaction is pref. carried out in the presence of a polar solvent such as water, alcohol, glycol, acetonitrile, DMF, etc.