Hydrolysis and other Cleavages of Glycosidic Linkages in Polysaccharides

This chapter discusses the cleavage of glycosidic linkages useful for the analysis of oligo- and polysaccharides. The cleavage of glycosidic linkages of larger oligo- and polysaccharides is necessary to determine the monosaccharides that compose the larger carbohydrate. Hydrolysis—that is, the cleavage of a bond by the addition of the elements of a water molecule, is the most common method for the cleavage of glycosidic linkages. Hydrolysis is carried out in aqueous solutions with an acid catalyst, although some special-purpose hydrolyses, such as the liberation of carbohydrate chains from glycoconjugates, require alkaline catalysts. Common acid catalysts are hydrochloric, sulfuric, and trifluoroacetic acids. Glycosidic linkages may also be cleaved in other solvents such as methanol. In this case, water is rigorously excluded so that the elements of a molecule of methanol are added across the glycosidic linkage to afford the methyl glycosides. Methanolysis is usually catalyzed by the addition of dry hydrogen chloride to methanol. Other solvents, such as acetic anhydride-acetic acid (acetolysis) and formic acid (formolysis), are occasionally used for special purposes.