One-Pot Azidochlorination of Glycals

A simple one-pot azidochlorination for the preparation of nitrogen-containing Kwoenigs-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 alpha-selective manner to the 2-azido glycosyl chlorides. Starting from disaccharide galactals, building blocks for the synthesis of the T-antigen are obtained in a straightforward manner. The simplicity of the reaction conditions allows for an efficient and scalable alpha-selective synthesis of 2-azido substituted glycosyl chlorides.