Two optically active (100% enantiomeric excess) isomers of ofloxacin [(+/-)-ofloxacin; DL-8280; (+/-)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7 H-pyrido[1,2,3-de] [1,4] benzoxazine-6-carboxylic acid] were prepared by use of their optically resolved synthetic intermediates. One of the isomers, (-)-ofloxacin, was 8 to 128 times more potent in inhibiting the multiplication of gram-positive and gram-negative bacteria than the other, (+)-ofloxacin, and approximately two times more active than the racemate, (+/-)-ofloxacin.

A series of novel chiral 7-(7-amino-5-azaspiro[2.4]heptan-4-yl)-8-chloro-1-(2-fluo rocyclopropyl)- quinolones were synthesized as a continuation of a research project of 1-(2-fluorocyclopropyl)-quinolones by considering stereochemical and physicochemical properties of the molecule. Absolute configurations of the 1-(cis-2-fluorocyclopropyl) moiety and the 7-(7-amino-5-azaspiro-[2.4]heptan-5-yl) moiety were determined by X-ray crystallographic analysis. Stereochemical structure-activity relationship studies indicated that 1-[(1R,2S)-2-fluorocyclopropyl] and 7-[(7S)-amino-5-azaspiro[2.4]heptan-5-yl] derivatives are more potent against Gram-positive and Gram-negative bacteria than the other stereoisomers and 7-[(7S)-7-amino-5-azaspiro[2.4]-heptan-5-yl]-8-chloro-1-[(1R ,2S)-2- fluorocyclopropyl]quinolone (33) is the most potent of all stereoisomers. Pharmacokinetic profiles and physicochemical properties of the selected compounds were also examined, and it was found that 33 (DU-6859a) possesses moderate lipophilicity and good pharmacokinetic profiles.

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A series of 1-(2-fluorocyclopropyl)-3-pyridonecarboxylic acids has been prepared. These derivatives are characterized by having a fluorine atom at the 2-position on the cyclopropane ring as the N1 substituent and consist of both cis and trans stereoisomers. Structure-activity relationship studies indicate that the cis derivatives are more potent against Gram-positive bacteria than the corresponding trans counterparts, but the difference in potency against most Gram-negative bacteria is much smaller. The inhibitory effect of compounds 4, 5, 26, 27, 38, and 39 on supercoiling activity of DNA gyrase obtained from E. coli KL-16 correlated with their MICs against the same strain and also depend on their (26, 27, 38, 39) stereochemistry. Introduction of a fluorine atom on the cyclopropyl group resulted in the reduction of lipophilicity compared with the corresponding nonfluorinated quinolones.

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