Regioselective Dechloroacetylations Mediated by Ammonium Acetate: Practical Syntheses of 2,3,4,6-Tetra-O-chloroacetyl-glycopyranoses and Cinnamoyl Glucose Esters

2,3,4,6-Tetra-O-chloroacetyl-glycopyranoses are key precursors for the formation of glycosyl donors which are important building blocks in carbohydrate chemistry. Inexpensive ammonium acetate (NH4OAc) was found to be an effective reagent for anomeric dechloroacetylations in carbohydrates, giving 2,3,4,6-tetra-O-chloroacetyl-glycopyranoses in excellent yields. This strategy is convenient for operation and purification, and thus suitable for the large-scale synthesis. Based on this methodology, two cinnamoyl glucose esters were successfully prepared.