Synthesis and Antibacterial Evaluation of Novel Fluoroquinolone Derivatives

A series of six novel 1-ethyl-6-fluoro-7-(4-(1-alkyl- 1,4-dihydropyridine-3-carbonyl)-piperazin-1-yl)-4-oxo-1,4- dihydro-quinoline-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. Nicotinoyl chloride was prepared by adopting reported procedures and was reacted appropriately with previously synthesized esters to yield the amides. Amides were converted into the corresponding quaternary compounds by reacting with suitable alkyl halides. The quaternary compounds were reduced in the inert atmosphere to yield the title compounds. 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 five different strains of bacteria. Compounds exhibited moderate to significant minimum inhibitory concentration.