CARBOXYLIC ACID DERIVATIVE AND PRODUCTION THEREOF

摘要

A compound represented by general formula (I), a compound represented by general formula (II), and a process for producing a compound represented by general formula (Ia) by the ring closure reaction of a compound represented by general formula (IIa) wherein R<1> represents hydrogen or alkyl; R<2> represents alkyl; R<3> represents hydrogen or acyl; R<4> represents -NH2 or -SCH2R<1>; and X represents hydrogen or chlorine. The invention process, using these compounds as the intermediates, can provide an alkyl 6,7-difluoro-1-methyl-4-oxo-4H-[1,3]thiazeto[3,2-a]quinolinecarboxylate in fewer steps than the conventional processes efficiently and economically.