Trifluoroacetolysis, a new method for structural studies of glycolipids.

Abstract

Trifluoroacetolysis is a reaction which is carried out in mixtures of trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) in various proportions and at different temperatures. 2-Acetamido-2-deoxy functions in sugar units are converted into 2-deoxy-2-trifluoroacetamido groups, by trifluoroacetolysis, employing TFA/TFAA in proportions varying from 1:1 to 1:50 at 100°C for 48 h (1). Under these conditions of trifluoroacetolysis most reducing sugars (2) and glycosides (3) are stable due to the stabilizing effects excerted by the O-trifluoroacetyl groups rapidly formed by the action of TFA/TFAA on the hydroxyl groups in the sugar residues. Peptide bonds are cleaved by transamidation and thus proteins and the protein part of glycoproteins will be degraded, by trifluoroacetolysis, whereas the carbohydrate portion of glycoproteins remains virtually intact, apart from some degradation of 2-acetamido-2-deoxy sugars situated at the reducing end (2,4,5). N-Glycosidically linked carbohydrate chains are cleaved off from glycoproteins by transamidation (4,5) and O-glycosidically linked carbohydrate chains are cleaved off from serine or threonine residues by an acid catalyzed elimination reaction (5,6).