(RS)-3-ethoxycarbonyl-7,9-difluoro-8-[3-(4-methoxyphenyl)-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine 在
7,9-difluoro-8-[3-(4-methoxyphenyl)-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid 作用下,
以
氢氧化钾 、
乙醇 为溶剂,
以(RS)-7,9-difluoro-8-[3-(4-methoxyphenyl)-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid (2 g) is obtained in the form of a yellow solid, m.p. 288°-290° C.的产率得到7,9-difluoro-8-[3-(4-methoxyphenyl)-1-piperazinyl]-1-methyl-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylic acid