Synthesis and antibacterial evaluation of novel 4-alkyl substituted phenyl beta-aldehyde ketone derivatives

A series of novel 4-alkylphenyl beta-aldehyde ketones and their derivatives were designed and synthesized on the basis of the chemical structures of Houttuynin and beta-lactam antibiotics. Antibacterial activities of these compounds were investigated. The results demonstrated that most of the compounds tested had moderate antibacterial activities against gram-positive pathogen Staphylococcus aureus (ATTC-25923) than Houttuynin, and gram-positive bacteria were more susceptible to the compounds than gram-negative bacteria. Compound 23 was found to be the most potent compound with MIC of 1.0 microg/mL against S. aureus. Particularly, compounds 16, 22 and 23 showed more active antibacterial activities against the clinically important pathogenic bacteria, methicillin-resistant S. aureus (MRSA) than Houttuynin and levofloxacin. The preliminary structure-activity relationship (SAR) analysis suggested that (1) the introduction of appropriate alkyl substituents into position 4 of phenyl ring enhanced antibacterial activities of these compounds, and isopropyl substituent might be more favorable; (2) the presence of ketone carbonyl moiety might play a vital role in determining significant antibacterial activities of these compounds.