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2-Amino-2-deoxysugars are naturally occurring molecules which play a key role in a number of biological and physiological events, such as molecular and immuno-recognition, as well as cell adhesion and differentiation. However, the chemical synthesis of these amino sugars, and particularly of oligosaccharides incorporating them, is still very challenging. A simple one-pot azidochlorination for the preparation of nitrogen-containing Koenigs-Knorr glycosyl donors proceeds upon reaction of protected glycals with sodium azide, ferric chloride, and hydrogen peroxide. Different mono- and disaccharide galactals and glucals are converted in a highly α-selective manner to the 2-azido glycosyl chlorides. Starting from disaccharide galactals, building blocks for the synthesis of the T-antigen, a tumor-associated carbohydrate antigen, are obtained in a straightforward manner. The simplicity of the reaction conditions allows for an efficient and scalable α-selective synthesis of 2-azido substituted glycosyl chlorides.
C. Plattner, M. Höfener, N. Sewald, Org. Lett. 2011, 13, 545–547.