Structural optimization of novel 1,3,4-oxadiazole-based antibacterial compounds for improved stability.

Abstract

A 1,3,4-oxadiazole-based compound named 1771 and its derivatives have been reported to exhibit antibacterial activity against Gram-positive bacteria, with activity extending to Gram-negative pathogens upon disruption of the outer membrane permeability barrier and/or efflux pump systems. However, the precise mode of action of these compounds remains unknown, and their utility is limited by low metabolic stability. Here, we describe the design and evaluation of analogues aimed at improving metabolic stability while defining the structural features required for antibacterial activity. Structure activity relationship analysis identified the secondary amide and the phenyl group as essential for antibacterial activity. Introduction of a para-pentafluorosulfanyl (SF5) substituent yielded compound 9b, which showed improved antibacterial potency and microsomal stability when compared to 1771. Although 9b remained suboptimal in microsomal stability, it provided the best overall balance of antibacterial activity and metabolic profile. Overall these results define key structural requirements for activity and provide a foundation for further optimization of this oxadiazole-based antibacterial scaffold, while providing key insights that may aid in identifying the compound's molecular target.