The (alpha-1,6) glycosidic bond of isomaltose: a tricky system for theoretical conformational studies.

Stable conformations of beta-isomaltose (alpha-D-glucopyranosyl-(1-->6)-beta-D-glucose) in gas-phase and aqueous solution are investigated in this study using quantum mechanical calculations. Conformational maps are calculated at HF/6-31G(d,p) level and lower energy structures are sampled in the most stable regions. Entropic and thermal corrections are considered and the Boltzmann population is obtained for conformers that are representative of the 18 most stable regions found on the potential energy surface.