Synthesis of a branched chain aza-C-disaccharide via the cycloaddition of a chiral nitrone to an alkene, both sugar derivatives

A multistep synthesis of a protected aza-C-disaccharide derivative with a pyrrolidine ring as the azasugar component is described. The key step is a stereoselective cycloaddition reaction of a chiral nitrone derived from D-ribose and a sugar alkene derived from D-galactose. An intramolecular N-alkylation followed by a reductive cleavage of the isoxazolidine N–O bond, in one pot, gave the final product.