SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF METHYL 2-O-(ALPHA-D-MANNOPYRANOSYL)-ALPHA-D-MANNOPYRANOSIDE

NMR experiments such as steady state NOE experiments and spin lattice H-1 relaxation time measurements were performed on the synthetic disaccharide 10 that constitutes part of the polysaccharide backbone in fungal mannans. The spectroscopic data were compared with a theoretical model that is based upon the HSEA force field and statistical mechanics, taking into account the flexibility around the glycosidic linkage. Potential energy calculations were performed with a modified version of the GESA program in order to derive the global minimum conformation of disaccharide 10 and to calculate ensemble average NOE and T1 values by averaging all energetically accessible conformational microstates, using a normalized Boltzmann distribution function. The fit between experimental and theoretical results improved significantly when we applied a dynamic model instead of a single state model based solely on the global minimum conformation of 10. Efficient synthesis of 10 was achieved by a recently published protocol for the in situ activation of thioglycosides.