The solution conformation of the disaccharide of avermectin B_la was examined by combining NMR data with theoretical conformational energy calculations.
Carbon and proton resonances were assigned unambiguously using high-field, high-resolution 2D NMR correlation spectroscopy. ³J_HH coupling constants were determined at 600 MHz.
The minimum-energy conformation was attained through an extended hard-sphere exo-anomeric effect (HSEA) approach. The HSEA conformation was refined by considering the experimental nuclear Overhauser enhancement contacts. The resulting three-dimensional structure was confirmed by comparing its glycosidic dihedral angles to those calculated from experimental ³J_COCH coupling constants.
Differences has been found in the glycosidic dihedral angles between the solution conformation and the X-ray structure.