Sulphates of monosaccharides and derivatives: Part IX. The conformations of glycoside sulphates in solution determined by N.M.R. spectroscopy

Abstract

The chemical shifts and coupling constants for the protons in a number of α- d-glucopyranoside and α- and β- d-galactopyranoside sulphates have been measured in aqueous solution. The values recorded are in agreement with a C1( d) conformation for both series of glycoside sulphates. The deshielding effect of the sulphate group on geminal and vicinal protons has been determined. A geminal proton is deshielded by about 0.6 p.p.m., but some variation with orientation is apparent. The effect of a sulphate group on a vicinal proton is dependent on the relative orientations of the two groups, and is largest when both groups are equatorial in the pyranoside ring. The solvent shift produced by adding pyridine to the aqueous solution of the glycoside sulphates is a useful indication of the position occupied by the sulphate group, since protons geminal to sulphate groups move rapidly downfield relative to the other sugar protons, but not as rapidly as the HOD line.