N-Acetyl-d-galactosamine (2-acetamido-2-deoxy-d-galactose, d-GalNAc) is a constituent of glycoproteins, glycolipids, and polysaccharides that play important roles in physiological events. Natural sources for this compound are rather limited, the main source being chondroitin sulfates, which is an expensive commodity. For this reason, development of powerful synthetic strategies for the preparation of d-GalNAc has been focused mainly at conversion of N-acetyl-d-glucosamine, d-GlcNAc (1), to d-GalNAc. The classical approaches are based on the multi-step protection reactions of d-GlcNAc to provide a precursor whose 4-hydroxy free group can be epimerized.
