Synthesis and Antibacterial Activity Against MRSA of Pleuromutilin Derivatives Possessing a Mercaptoethylamine Linker

Background: Methicillin resistant Staphylococcus aureus (MRSA) usually invalidate powerful antibiotics in the clinic. Pleuromutilin derivatives have been reported to possess antibacterial activity against MRSA. Objective: The antibacterial activities against MRSA of a series of thirteen synthetic pleuromutilin derivatives were investigated through in vitro models. Methods: A series of novel thioehter pleuromutilin derivatives incorporating various aromatic substituents into the C14 side chain have been reported. The in vitro antibacterial activities of these derivatives against MRSA and Escherichia coli were tested by the broth dilution method. Results: Twelve pleuromutilin derivatives were designed, synthesized and evaluated for in vitro antibacterial activities against four Staphylococcus aureus strains. From structure-activity relationship studies, compound 11c was identified as promising compounds with the most potent in vitro antibacterial activity among the series (MIC = 0.0625-0.125 μg/ml) against Staphylococcus aureus strains. The binding of compound 11c to the 50s ribosome was investigated by molecular modeling. Conclusion: It was found that there is a reasonable correlation between the binding free energy and the antibacterial activity.