Synthesis of balofloxacin,the forth generation fluoroquinolone

Aim To synthesize the forth generation fluoroquinolone balofloxacin.Method Balofloxacin was synthesized by condensation of 1-cyclopropyl-6,7difluoro-1,4-dihydro-8-methoxy-4-oxo-3-quinolinecarboxylic acid with 3methylaminopiperidine in the presence of trimethoxyborane.The key intermediate 3-methylaminopiperidine was synthesized from 3-methylaminopyridine by two methods,formylation and lithium aluminium hydride reduction or condensation with triethyl orthoformate and sodium borohydride reduction,and then hydrolysis.Its chemical structure was identified with()~1H-NMR and IR.Results The structure was identified by spectra.The over all yield of balofloxacin was 60%,the two methods to the synthesis of 3-methylaminopyridine with the overall yield of 16% and 32%.Conclusions The synthetic method is improved and the cost is reduced.It is available to the synthesis of balofloxacin.