Glycosyl donors in “unusual” conformations – influence on reactivity and selectivity

The huge majority of glycosylation and other reactions at the anomeric centre of carbohydrates have been performed with the saccharide in its most stable, commonly chair, conformation. Nevertheless, the outcome of these reactions has been found to depend on the conformation of the saccharide residue. This article reviews glycosylation and the glycoside hydrolysis reaction with saccharide derivatives that have been forced, for instance by special protection groups, tethering, etc., into an unusual conformation.