A Methyl 4-Oxo-4-phenylbut-2-enoate with Activity against MRSA that Inhibits MenB in the Bacterial Menaquinone Biosynthesis Pathway.

4-Oxo-4-phenyl-but-2-enoates inhibit MenB, the 1,4-dihydroxyl-2-naphthoyl-CoA synthase in the bacterial menaquinone (MK) biosynthesis pathway, through the formation of an adduct with coenzyme A (CoA). Here, we show that the corresponding methyl butenoates have MIC values as low as 0.35-0.75 µg/mL against drug sensitive and resistant strains of . Mode of action studies on the most potent compound, methyl 4-(4-chlorophenyl)-4-oxobut-2-enoate (), reveal that is converted into the corresponding CoA adduct in cells, and that this adduct binds to the MenB (MenB) with a value of 2 µM. The antibacterial spectrum of is limited to bacteria that utilize MK for respiration, and the activity of can be complemented with exogenous MK or menadione. Finally, treatment of methicillin-resistant (MRSA) with results in the small colony variant phenotype and thus phenocopies knockout of the gene. Taken together the data indicate that the antibacterial activity of results from a specific effect on MK biosynthesis. We also evaluated the efficacy of using two mouse models of MRSA infection. Notably, compound increased survival in a systemic infection model and resulted in a dose-dependent decrease in bacterial load in a thigh infection model, validating MenB as a target for the development of new anti-MRSA candidates.