NMR-SPECTROSCOPY OF HYDROXY PROTONS OF 3,4-DISUBSTITUTED METHYL ALPHA-D-GALACTOPYRANOSIDES IN AQUEOUS-SOLUTION

The H-1 NMR chemical shifts, coupling constants, temperature coefficie nts, exchange rates, inter-residue NOEs, and the deuterium isotope eff ects on C-13 chemical shifts have been measured, in aqueous solution, for the hydroxy protons of two 3,4-disubstituted galactopyranosides, u cp-(1-->3)-[alpha-L-Fucp(1-->4)]-alpha-D-Galp-OMe and cp-(1-->3)-[beta -D-Glcp-(1-->4)]-alpha-D-Galp-OMe, and their constituent monomeric met hyl glycosides. All the hydroxy proton resonances could be assigned an d for both trisaccharides the data indicated hydrogen bonding interact ions between the hydroxy groups at the C-2 position of the two non-red ucing sugars. Using the hydroxy protons, the number of inter-residue N OEs for the two trisaccharides was increased from 4 to 6 and from 4 to 7, respectively, relative to those obtained in D2O solutions. These r esults show that the NMR data obtained from hydroxy protons can provid e important information in terms of hydrogen bonding interactions and inter-residue NOEs, which could be further used in structural and conf ormational analysis to improve the characterisation of oligosaccharide s in aqueous solution.