Synthesis and antibacterial evaluation of certain quinolone derivatives

A number of 7-substituted quinolone derivatives were synthesized and evalua ted for antibacterial and cytotoxic activities. Preliminary results indicat ed that most compounds tested in this study demonstrated better activity ag ainst methicillin-resistant Staphylococcus aureus than norfloxacin. Among t hem, 1-(4-amino-2-fluorophenyl)-6-fluoro-1,4-dihydro-7-{4-[2-(4-methoxyphen yl)-2-hydroxyiminoethyl]-1-piperazinyl}-4-oxo-3-quinolinecarboxylic acid (1 1d) and its ketone precursor 10d exhibited significant activities against K lebsiella pneumoniae, methicillin-resistant S. aureus, erythromycin- and am picillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enter ococcus faecalis. Due to strong cytotoxicities of lid (a mean log GI(50) of -5.40), compound 10d, with good antibacterial activities and low cytotoxic ities (a mean log GI(50) of -4.67), is a more potential drug candidate.