2-苯基哌嗪   、                                                                                      
ethyl 1-cyclopropyl-7,8,9-trifluoro-4-oxo-1,4-dihydrobenzo[b][1,8]naphthyridine-3-carboxylate                                                                                                                                                              在
                                                                                                                                                                                 
(RS)-1-cyclopropyl-3-ethoxycarbonyl-7,9-difluoro-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine   、                                                                                                  
N,N-二甲基甲酰胺   、                                                                                                  
乙醇                                                                                                                                  作用下,
                                                                                                                                                                                                                            以(RS)-1-cyclopropyl-3-ethoxycarbonyl-7,9-difluoro-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine (1.8 g) is obtained in the form of a yellow solid, m.p. 242° C.的产率得到(RS)-1-cyclopropyl-3-ethoxycarbonyl-7,9-difluoro-4-oxo-8-(3-phenyl-1-piperazinyl)-1,4-dihydrobenzo[b][1,8]naphthyridine