High-field nuclear magnetic resonance and molecular dynamics investigations of alditol conformations in aqueous and non-aqueous solvents

Abstract

³ J coupling constants for five ²H-exchanged alditols in D₂O and [²H₅]pyridine have been determined at 25 °C after refinement of the fully resolved ¹H NMR spectra obtained at 620 MHz. Concurrently, molecular dynamics simulations have been performed of two of the molecules (mannitol and glucitol) in SPC/E water and in an argon-like solvent, by means of which the torsional angles and their flexibilities have been determined and compared to those derived from an analysis of the ³J values with the aid of the Karplus equation. The results are interpreted in terms of different populations of rotamers which are sensitive to stereochemical detail and to the solvent medium. Although there is a reasonable level of agreement between the NMR-based and simulation results, some discrepancies remain and are discussed.