Reagents and conditions: for 37: Ac2O (1.5 equiv), pyridine, 60 °C, 95%; for 38: benzoic acid (2.0 equiv), 2,4,6-trichlorobenzoyl chloride (2.5 equiv), Et3N (3.0 equiv), 4-DMAP (catalytic), toluene, 90%; for 39: cinnamic acid (2.0 equiv), 2,4,6,-trichlorobenzoyl chloride (2.5 equiv), Et3N (3.0 equiv), 4-DMAP (catalytic), toluene,88%.