Design, Syntheses, and Anti-TB Activity of 1,3-Benzothiazinone Azide and Click Chemistry Products Inspired by BTZ043

Electron deficient nitroaromatic compounds such as BTZ043 and its closest congener, PBTZ169, and related agents are a promising new class of anti-TB compounds. Herein we report the design and syntheses of 1,3-benzothiazinone azide (BTZ-N3) and related click chemistry products based on the molecular mode of activation of BTZ043. Our computational docking studies indicate that BTZ-N3 binds in the essentially same pocket as that of BTZ043. Detailed biochemical studies with cell envelope enzyme fractions of Mycobacterium smegmatis combined with our model biochemical reactivity studies with nucleophiles indicated that, in contrast to BTZ043, the azide analogue may have a different mode of activation for anti-TB activity. Subsequent enzymatic studies with recombinant DprE1 from Mtb followed by MIC determination in NTB1 strain of Mtb (harboring Cys387Ser mutation in DprE1 and is BTZ043 resistant) unequivocally indicated that BTZ-N3 is an effective reversible and noncovalent inhibitor of DprE1.