The effect of stereochemistry upon carbohydrate hydration. A molecular dynamics simulation of β-d-galactopyranose and (α,β)-d-talopyranose

This paper reports a molecular dynamics simulation study of β-d-galactopyranose and (α,β)-d-talopyranose in aqueous solution. Special emphasis was placed on the intramolecular next-nearest neighbour oxygen distances in the carbohydrate molecule and the hydrogen bonding of the hydroxy functionalities of the carbohydrates with water. The average number of hydrogen bonds of the hydroxy groups of the carbohydrates depends on the stereochemistry of the molecule. In contrast to the HO-2 and HO-4 of d- galactopyranose, those of d-talopyranose are shielded. This is a consequence of an intramolecular hydrogen bond between the HO-2 and HO-4 in d-talopyranose, which also explains why the apparent hydrophobicity of d-talose is found to be greater than that of d-galactose.