Synthesis of possible metabolites of 1-cyclopropyl-1,4-dihydro-6-fluoro-5-methyl-7-(3-methyl-1-piperazinyl)- 4-oxo-3-quinolinecarboxylic acid (Grepafloxacin, OPC-17116).

Grepafloxacin (1-cyclopropyl-1,4-dihydro-6-fluoro-5-methyl-7-(3-methyl-1-piperazinyl )-4-oxo-3-quinoline-carboxylic acid, OPC-17116) (1) exhibits potent and broad-spectrum in vitro and in vivo antibacterial activity. In order to identify the structures of the metabolites of grepafloxacin, 17 possible metabolites were prepared. Among them, 6 compounds were found to be actual metabolites (2a, b, 4a, b and 6a, b) of grepafloxacin in rats, dogs and/or humans. The antibacterial activities of these metabolites were found to be weaker than that of grepafloxacin.