SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF )-6-FLUORO-1,4-DIHYDRO-4-OXOQUINOLINE-3-CARBOXYLIC ACIDS AND THEIR 6,8-DIFLUORO ANALOGS

Alkylation of 6,7-difluoro-4-hydroxyquinoline-3-carboxylic acid ethyl ester with substituted-benzyl chlorides gave 7-difluoro-1,4-dihydro-4- oxoquinoline-3-carboxylic acid ethyl esters. Their treatment with pipe razine or N-methylpiperazine in pyridine yielded ydro-4-oxo-7-(1-piper azinyl)quinoline-3-carboxylic acid ethyl esters which were hydrolyzed with aqueous sodium hydroxide and then acidified with hydrochloric aci d afforded the desired ydro-4-oxo-7-(1-piperazinyl)quinoline-3-carboxy lic acids. The 6,8-difluoro analogs were prepared similarly using 6,7, 8-trifluoro-4-hydroxyquinoline-3-carboxylic acid ethyl eater as a star ting material. Some of these quinolones demonstrated fairly good antib acterial activities. Among them, ydro-7-(1-piperazinyl)-4-oxoquinoline -3-carboxylic acid (7d) and ydro-7-(1-piperazinyl)-4-oxoquinoline-3-ca rboxylic acid (8c) are two of the best.