CONFORMATIONAL MOBILITY OF OLIGOSACCHARIDES - EXPERIMENTAL-EVIDENCE FOR THE EXISTENCE OF AN ANTI CONFORMER OF THE GA1-BETA-1-3GLC-BETA-1-OME DISACCHARIDE

A hydrogen bond between the Glc OH(4) and Gal OH(2) groups of the title disaccharide, manifested by the doubling of their H-1 NMR signals in a partially deuteriated sample in Me(2)SO solution, proves the existence of an ''anti'' conformer, i.e., one with the anomeric and transglycosidic aglyconic C-H bonds turned away from each other by similar to 180 degrees. This conformer is at equilibrium with the predominating normal ''syn'' conformation(s), as shown by the analysis of several interresidue NOEs, and confirmed by molecular mechanics and molecular dynamics calculations.