Selective benzoylation of methyl 2-benzamido-2-deoxy-α-D-glucopyranoside: a convenient preparation of derivatives of 2-amino-2-deoxy-D-galactose

Abstract

Selective dimolar benzoylation of methyl 2-benzamido-2-deoxy-α-D-glucopyranoside yielded the 3,6-di-O-benzoate, which was converted into the 4-O-methanesulphonate in 52% overall yield. This sulphonate underwent a replacement reaction with inversion of configuration at carbon 4 when treated with sodium benzoate in NN-di-methylformamide, to give methyl 2-benzamido-2-deoxy-α-D-galactopyranoside tri-O-benzoate, the structure of which was demonstrated by ¹H n.m.r. spectroscopy and by its conversion into the known methyl 2-acetamido-2-deoxy-α-D-galactopyranoside. The isomeric methyl 2-benzamido-4,6-di-O-benzoyl-2-deoxy-3-O-methylsulphonyl-α-D-glucopyranoside was prepared by a definitive route for comparison.