Small molecules with oxathiazol-2-one moiety were recently reported as potent inhibitors of Mycobacterium bovis var. bacilli Calmette–Guérin (BCG), among which HT1171 was the most potent and selective proteasome inhibitor. Herein we synthesized a series of novel compounds by bioisosteric replacement of the oxathiazol-2-one ring with 3H-1, 2, 4-dithiazol- 3-one, and also fifteen 1, 3, 4-oxathiazol-2-one molecules in order for potency comparison ...