Intermediates for the synthesis of benzimidazole derivatives and a process for the preparation thereof

摘要

This invention provides a process for the preparation of a benzimidazole derivative (I) or a pharmaceutically acceptable salt thereof, wherein R1 is C1-C6 alkyl, C1-C6 alkoxyl, etc., R2 is C1-C6 alkyl, and R3 is hydrogen or a protecting group, which exhibits excellent hyopoglycemic action, said process comprising condensation of an amine derivative (III) with a carboxylic acid derivatives (II) to afford a compound (IV), followed by cyclization of compound (IV) in the presence of an acid.