Evaluation of steric effects on the exocyclic conformations of 6-C-methyl-substituted 2-acetamido-2-deoxy-beta-D-glucopyranosides.

Introduction of a stereodefined methyl group at the C-6 position of N-acetylglucosamine mono- and disaccharides creates a strong and predictable orientational bias on the geminal C-6 hydroxyl in solution, as determined by (1)H-(1)H and (13)C-(1)H NMR coupling constants. The conformational directing effect is more pronounced in the disaccharides because of the greater steric demand imposed by the neighboring glycosidic unit.