PRODUCTION OF MERCAPTOIMIDAZOLE DERIVATIVE

PURPOSE:To obtain a compound useful as a synthetic intermediate, etc., for pilocarpine, etc., which is a therapeutic medicines of glaucoma by adding a water solution of acid adduct of a specific alpha-aminoketone derivative into a solution containing an isothiocyanic acid derivative and a base, reacting both derivatives and cyclizing the resultant compound. CONSTITUTION:An aqueous solution of an acid adduct of alpha-aminoketone derivative (e.g. aminomethylhomopilopyl ketone) expressed by formula I (R is H or lower alkyl) is added to a solution containing an isothiocyanic acid derivative (e.g. isothiocyanic acid methyl ester) and a base (e.g. potassium carbonate) together and reaction of the alpha-aminoketone with the isothiocyanic acid derivative is carried out while stirring the solution at ambient temperature for l hr. Then, the reaction system is acidified by adding concentrated hydrochloric acid to the resultant thiourea derivative expressed by formula II to carry out cyclizing reaction and the reactional liquid is concentrated under reduced pressure and the residue is cooled and crystallized by adding water to the residue to provide the mercaptoimidazole derivative expressed by formula III and useful as a synthetic intermediate, etc., for pilocarpine which is a therapeutic medicine for glaucoma and its analogue compounds.