MEASUREMENT OF INTERGLYCOSIDIC (3)J(CH) COUPLING-CONSTANTS OF SELECTIVELY C-13 LABELED OLIGOSACCHARIDES BY 2D J-RESOLVED H-1-NMR SPECTROSCOPY

Tri-, tetra-, and penta-saccharide fragments of the O-specific polysac charide of Shigella dysenteriae type 1 have been prepared in which a D -galactose residue of each oligosaccharide methyl glycoside derivative contains a C-13 label at C-1. The interglycosidic coupling constants ((3)J(CH)) of these C-13 nuclei with the H-3 nuclei of the adjacent 2- acetamido-2-deoxy-D-glucose residues have been measured by two-dimensi onal, J-resolved H-1 NMR spectroscopy. The magnitudes of these couplin g constants indicate that the trisaccharide is conformationally differ ent to the higher oligosaccharide homologs, in agreement with previous studies of C-13 chemical shifts and (1)J(CH) values. (C) 1998 Elsevie r Science Ltd. All rights reserved.