Synthesis and antibacterial activity of some novel N-substituted piperazinyl-quinolones.

A series of N-substituted-piperazinyl-quinolones were synthesized and evaluated for in vitro antibacterial activity. Compounds with a 2-(2,4-dichlorophenyl)-2-oxoethyl group attached to the piperazine ring (5a-c) had similar antibacterial activity to the reference drugs, ciprofloxacin, norfloxacin and enoxacin against both Gram-positive and Gram-negative bacteria. The oximes 6a-c and 6g-i were almost less active than corresponding ketones against the tested microorganisms, however the 2,4-difluorophenyl analogues (6g-i) were more active than 2,4-dichlorophenyl derivatives (6a-c). If the hydrogen of oxime is replaced with a benzyl group (6d-f & 6j-l), in-vitro antibacterial activity was decreased against both Gram-positive and Gram-negative bacteria. Generally ciprofloxacin derivatives were more active than norfloxacin and enoxacin derivatives.