An efficient conversion of N-acetyl-D-glucosamine to N-acetyl-D-galactosamine and derivatives.

2-Acetamido-2-deoxy-D-galactose (d-GalNAc) is an important monosaccharide widely distributed in nature. However, unlike its 4-epimer, the 2-acetamido-2-deoxy-D-glucose (D-GlcNAc), D-GalNAc is very expensive to obtain from commercial sources. Herein we report an efficient transformation that allows for the conversion of D-GlcNAc to a D-GalNAc derivative 7 in three steps and in 58.4-75% overall yields. The process was carried out on a greater than 20-g scale without the need of chromatography. The versatility of compound 7 was demonstrated by the synthesis of several useful monosaccharides and thiodisaccharides containing a D-GalNAc residue.