PURPOSE: To obtain melatonine (N-acetyl-5-methoxytributamine) having control activity of day periodic cycles, ovulation induction activity and sleeping induction activity by methylating N-acetyl serotonine in the 5-position.

CONSTITUTION: The N-acetyl srotonine is methylated in the 5-position under a tamp. condition of not exceeding 45°C at pH larger than 11 by using preferably excessive dimethyl sulfate as a methylating agent, by which the melatonine useful also as an intermediate for mexamine (5-methoxy tributamine hydrochloride) having sedative and radiation protective action is obtd. The raw material described above is produced by acetylating the serotonine obtd. preferably from coffee wax to form N,O-diacetyl serotonine, then selectively hydrolyzing this O-acetyl group by using an alkaline liquid mixture composed of water and lower alcohol.