Protecting Groups in Carbohydrate Chemistry

The most important protecting groups in carbohydrate chemistry are reviewed. The paper is aimed at those beginning to specialize in synthetic carbohydrate chemistry and at teachers with other specialties who wish to go beyond the content of general organic chemistry textbooks. Acetals and ketals are of fundamental importance in carbohydrate chemistry and their chemistry is presented first. In contrast to the base stability of the acetals, are the base labile esters. The complimentary use of these two protecting methods is illustrated. Methyl and benzyl ethers have a long history both in synthetic carbohydrate chemistry and in the structural studies of polysaccharides. In synthetic work benzyl ethers are the most useful. Silyl ethers are also well established in carbohydrate chemistry and the use of these protecting methods is illustrated. Phase transfer reactions and the use of cyclic stannylene derivatives to enhance the regioselectivity in the introduction of protecting groups, especially ethers, is discussed as well as some results optained with stannous chloride catalyzed reactions of diaryldiphenylmethanes with vicinal diols which gave unexpected results. The paper ends with illustrative examples of the use of protecting groups in modern synthetic carbohydrate chemistry, namely the synthesis of nitrogen containing compounds belonging to an important class of polyhydroxylated cyclic amines. Compounds of this class are potent inhibitors of glycosidase enzymes.