Structure-activity relationship of the caprazamycin core with selected antimicrobial activity against Mtb H37Rv. Conditions: a) 80% AcOH/H2O; b) Boc2O, triethylamine, 1,4-dioxane(aq); c) R-NH2, bis(2-oxo-3-oxazolidinyl)phosphinic chloride (BOP-Cl), triethylamine, THF, or R-NH2, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM), 2-propanol(aq); d) R-OH, BOP-Cl, pyridine; e) trifluoroacetic acid, MeOH.