Deacetylation of per-acetatylated glycopyranosides: An overall pattern for acidic catalyzis

Acetyl protecting groups are commonly used in carbohydrate chemistry. Partially acetylated arylglycosides are not only useful building blocks in syntheses, but they are also substantial for plant metabolism. Nonselective base catalysis is often used for removing the acetyl groups. Even though acid-catalyzed deacetylation might be more selective, it is seldom used in carbohydrate chemistry, because it has not been thoroughly investigated. In this work, we study the acid-catalyzed deacetylation of per-acetylated phenyl glycosides experimentally and computationally by using density functional theory (DFT) calculations. Based on quantum modeling, we design a general scheme for the stepwise acid-catalyzed deacetylation of arylglycosides per-acetates. The approach can also be applied on gluco- and galactopyranosides. We have studied the deacetylation reaction in solvents of different polarity and found that the activation barriers of the stepwise deacetylation mechanism increase with increasing polarity of the solvent.