Rapid glycosylations under extremely mild acidic conditions. Use of ammonium salts to activate glycosyl phosphites via P-protonation

Trifluoromethanesulfonic acid salts of tertiary amines were employed as extremely mild acidic activators for rapid glycosylations. Glycosyl phosphite triesters bearing an acid-labile 4,4′-dimethoxytrityl (DMTr) group for transient protection worked as glycosyl donors effectively in the presence of the activators to afford the corresponding disaccharides in good yields without loss of the DMTr group.