Carboxylate Surrogates Enhance the Antimycobacterial Activity of UDP-Galactopyranose Mutase Probes

Uridine diphosphate galactopyranose mutase (UGM also known as Glf) is a biosynthetic enzyme required for construction of the galactan, an essential mycobacterial cell envelope polysaccharide. Our group previously identified two distinct classes of UGM inhibitors; each possesses a carboxylate moiety that is crucial for potency yet likely detrimental for cell permeability. To enhance the antimycobacterial potency, we sought to replace the carboxylate with a functional group mimican <i>N</i>-acylsulfonamide group. We therefore synthesized a series of <i>N</i>-acylsulfonamide analogs and tested their ability to inhibit UGM. For each inhibitor scaffold tested, the <i>N</i>-acylsulfonamide group functions as an effective carboxylate surrogate. Although the carboxylates and their surrogates show similar activity against UGM in a test tube, several <i>N</i>-acylsulfonamide derivatives more effectively block the growth of <i>Mycobacterium smegmatis</i>. These data suggest that the replacement of a carboxylate with an <i>N</i>-acylsulfonamide group could serve as a general strategy to augment antimycobacterial activity.