Design, synthesis and antibacterial evaluation of novel pleuromutilin derivatives possessing piperazine linker

A series of pleuromutilin derivatives bearing piperazine ring have been reported. The in vitro antibacterial activities of the synthetic derivatives against MRSA (ATCC 43300), Staphylococcus aureus (ATCC 29213), Enterococcus faecalis (ATCC 29212), Enterococcus faecium (ATCC35667) and Escherichia coli (ATCC25922) were evaluated by the broth dilution method. Most of the synthesized derivatives displayed potent activities. Compounds 11c, 12a and 12c were found to be the most active antibacterial derivatives against MRSA (minimum inhibitory concentration = 0.015 μg/mL). The binding of compounds 11c, 12a and 12c to the 50s ribosome were investigated by molecular modeling. Compound 11c possessed lower binding free energy compared with compounds 12a and 12c. Compound 11c was further evaluated in MRSA systemic infection model and displayed superior in vivo efficacy to that of tiamulin.