Synthesis and in-vitro antibacterial activity of/N-piperazinyl quinlone derivatives with 5-chloro-2-thienyl group

Fluoroquinolones are an important group of antimicrobial agents that are used widely in the treatment of various infectious diseases. The purpose of the present study was to synthesize new N-piperazinyl quinolone derivatives with 5-chloro-2-theinyl group having possible antimicrobial activity. Reaction of ciprofloxacin [1], norfloxacin [2] and enoxacin [3] with alpha-bromoketone 10 or alpha-bromooxime derivatives 11a-c in DMF, in the presence of NaHCO[3] at room temperature, afforded corresponding ketones 4a-c or oxime derivatives 5-7[a-c], respectively. The synthesized compounds were tested against a series of Gram-positive and Gram-negative bacteria. The results of MIC tests against both Gram-positive and Gram-negative bacteria revealed that ciprofloxacin derivatives [compounds 4a, 5a, 6a and 7a] were more active than norfloxacin and enoxacin analogues. Compound 5a, containing N-[2-[5-chlorothiophen-2-yl]-2-hydroxyiminoethyl] residue provided a high in vitro antibacterial activity against Gram-positive bacteria, with MIC of 0.06, 0.125, 0.5 and 0.125 micro g/mL against S. aureus, S. epidermidis, E. feacalis and B. subtilis, respectively. Its activity was found to be 4 to 8 times better than reference drug [ciprofloxacin] against all Gram-positive bacteria with the exception of E. feacalis