Synthesis and evaluation of probe 19. (a) Lowest energy binding poses in the active site of Ag85c of trehalose 1 (cyan), TMH 2b (green), 17 (yellow) and 19 (magenta). The active site serine is shown with an arrow. Image produced using PyMol26 and docking poses generated with AutoDock Vina27 from pdb 1DQZ (b) Synthesis of inhibitors 17 and 19. Reagents and conditions: i) hexyldichlorophosphate, pyridine, rt, 16h; ii) 1:1 EtOH/H2O, Pd-C, H2, rt, 18h; iii) BTFFH, DIPEA, DMF, rt, 18h; iv) 1:1 EtOH/H2O, Pd-C, H2, rt, 18h. (c) Reaction of probe 19 with Ag85c indicates essentially complete conversion to covalently modified Ser124 adduct by ES-MS.