A practical synthesis of (S)-(-)-nadifloxacin: Novel acid-catalyzed racemization of tetrahydroquinaldine derivative

Article abstract of DOI:10.1248/cpb.44.642

(S)-(-)-Nadifloxacin [(S)-(-)-9-fluro-6,7-dihydro-8-(4-hyroxy-1- piperidyl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic acid, (S)- (-)-OPC-7251], an antibacterial agent, was synthesized from (S)-(-)-5,6- difluoro-2-methyl-1,2,3,4-tetrahydroquinoline (DFTQ), which was prepared by the optical resolution of racemic DFTQ with 2,3-di-O-benzoyl-L-tartaric acid. Racemization of the undesired enantiomer [(R)-(+)-DFTQ] was studied in the presence of various acids and the best result was obtained in the case of methanesulfonic acid. The absolute configuraton of (-)-nadifloxacin was determined as S by X-ray crystallographic analysis.

Full text of DOI:10.1248/cpb.44.642

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