Synthesis and in-vitro antibacterial activity of some novel N-nicotinoyl-1-ethyl-6-fluoro-1,4-dihydro-7-piperazin-1-yl-4-oxoquinoline-3-carboxylates.

A series of N-nicotinoyl-1-ethyl-6-fluoro-1,4-dihydro-7-piperazin-1-yl-4-oxoquinoline-3-carboxylates has been synthesized and evaluated for antibacterial activity. Norfloxacin was reacted with thionyl chloride, to yield norfloxacin acid chloride which was used immediately in next step by reacting with respective alcohols to furnish the corresponding esters i.e. 1-ethyl-6-fluoro-1,4-dihydro-7-piperazin-1-yl-4-oxoquinoline-3-carboxylates (III). Nicotinoyl chloride (IV) was prepared by adopting reported procedures and was reacted appropriately with previously synthesized esters (III) to yield the title compounds (V). The structures of synthesized compounds were established on the basis of analytical and spectral studies. All the synthesized compounds were evaluated for antibacterial activity against four different strains of bacteria. Compounds exhibited moderate to significant minimum inhibitory concentration (MIC) values ranging from 0.19 to 0.37 against E. coli, 0.17 to 0.37 against S. dysentry. The MIC values against Gram positive bacteria were slightly more that Gram negative ones and ranged from 1.9 to 3.5 against S. aureus and 2.0 to 3.1 against B. subtilis.