Preparation of tagged glucose as a key intermediate in the synthesis of branched oligosaccharides

Tagged and activated d-glucose was introduced as a building block for branched oligosaccharides. This building block was the oligosaccharide branching point at which selectively the C-2 followed by the C-3 position can be glycosylated. After the activation of the C-1 position by oxidation of a thiophenyl group, the newly formed tagged oligosaccharide can be used as a glycoside donor. Synthetic procedures for the preparation of phthalimide-based tag molecules as well as tagged monosaccharides are presented.