Synthesis and antibacterial evaluation of certain quinolone derivatives

A number of 7-substituted quinolone derivatives were synthesized and evaluated for antibacterial and cytotoxic activities. Preliminary results indicated that most compounds tested in this study demonstrated better activity against methicillin-resistant Staphylococcus aureus than norfloxacin. Among them, 1-(4-amino-2-fluorophenyl)-6-fluoro-1,4-dihydro-7-[4-[2-(4-methoxyphenyl)-2-hydroxyiminoethyl]-1-piperazinyl]-4-oxo-3-quinolinecarboxylic acid (11d) and its ketone precursor 10d exhibited significant activities against Klebsiella pneumoniae, methicillin-resistant S. aureus, erythromycin- and ampicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecalis. Due to strong cytotoxicities of 11d (a mean log GI(50) of -5.40), compound 10d, with good antibacterial activities and low cytotoxicities (a mean log GI(50) of -4.67), is a more potential drug candidate.