High-pressure glycosylations of unreactive alcohols and the formation of N-glycosyl collidinium salts

The yields of disaccharide glycosylation products in tetramethylammonium bromide or silver triflate-collidine activated reactions between hindered alcohols and glycosyl halides were not greatly affected when a pressure of 15 kbar was applied. The formation of orthoester products was greatly increased under pressure. When orthoester formation was not possible both disaccharides and the related N-glycosyl collidinium salts were found.