Structures of Furanosides:  A Study of the Conformational Space of Methyl α-d-Lyxofuranoside by Density Functional Methods

A search of the gas phase conformational space of methyl α-d-lyxofuranoside was carried out at the B3LYP/cc-pVDZ level. Relative energies of the local minima were computed using the larger aug-cc-pVDZ basis set and the recent mPW1LYP exchange-correlation functional. Local minima include structures with zero, one, two, three, or four internal hydrogen bonds and conformational energies of 12−2 kcal/mol relative to the “strain-free” methyl α-d-lyxopyranoside. The two most stable structures, with three and four internal hydrogen bonds, have conformational energies of approximately 2 kcal/mol. The relevance of these results to the conformational behavior of furanosides in the crystalline state and in solution is discussed. An efficient and accurate general procedure for searching the conformational space of furanosides is proposed.