A Computational Study of Methyl α-D-Arabinofuranoside: Effect of Ring Conformation on Structural Parameters and Energy Profile

Abstract

Ab initio molecular orbital calculations at the HF/6-31G* level of theory and density functional theory calculations at the B3LYP/6-31G* level have been carried out on methyl α-d-arabinofuranoside (1). All 10 possible envelope forms were constructed and minimized, providing a partial energy surface which identified 3E as the lowest energy north conformer and, depending on the level of theory used, either 2E or E1 as the southern hemisphere minimum. The southern conformation was the global minimum regardless of the level of theory. The energy profile identifies pseudorotation through the eastern pathway as the most favorable. Pseudorotation through the west is higher in energy and similar to inversion through the planar species. The dependence of structural parameters (i.e., bond distances, bond angles, dihedral angles, and interatomic distances) on the ring conformation have been determined. Energy profiles based on additional electron correlation and extended basis sets with the HF/6-31G* geometries are presented and provide qualitatively similar results to the B3LYP/6-31G* profile.