Twisted Amides as Selective Acylating Agents for Hydroxyl Groups under Neutral Conditions:  Models for Activated Peptides during Enzymatic Acyl Transfer Reaction

The highly twisted amide 2 served as a selective acylating agent for diols under neutral conditions. The reaction of primary−secondary diols with 2 led to the corresponding primary alkyl monopivalates. For diols containing alcoholic and phenolic hydroxyl groups, alcoholic hydroxyl groups were selectively acylated under neutral conditions, whereas, the opposite selectivity was observed under basic conditions, similar to the cases using acyl halides or acid anhydrides. Although 1 and 3 were unreactive to alcohols, 5−10 having substituent groups at C-4 were reactive to alcohols to give the corresponding acetates or benzoates.