| Abstract: | As a part of metabolic studies of mosapride ( 1 ), a potential gastroprokinetic agent, the synthesis of 4-chloro-7-ethoxy-2(3H)-benzoxazolone-6-carboxylic acid ( 7 ) as a derivative of 4-amino-5-chloro-2-ethoxy-3-hydroxybenzoic acid ( 6 ), which has served a benzoic acid part of the metabolites 4 and 5 , is described. Treatment of methyl 3-amino-4-substituted amino-5-chloro-2-ethoxybenzoate derivatives 11a-c with sodium nitrate in acidic medium gave the benzotriazole derivatives 13x,y instead of the objective 3-hydroxy counterpart. The synthesis of 7 started from o-vanillin acetate ( 15 ) and proceeded through the intermediates 2-hydroxy-3-methoxy-4-nitrobenzaldehyde ( 18 ), methyl 4-amino-2,3-dihydroxybenzoate ( 23 ), and methyl 7-hydroxy-2(3H)-benzoxazolone-6-carboxylate ( 30 ). Compound 30 was alternatively prepared from 23 via methyl 4-ethoxycarbonylamino-2-ethoxycarbonyloxy-3-hydroxybenzoate ( 29 ), which is the product resulting from the migration of the ethoxycarbonyl group of methyl 4-amino-2,3-diethoxycar-bonyloxybenzoate ( 27 ). |
