Acetate groups as probes of the stereochemistry of carbohydrates: a vibrational circular dichroism study

Vibrational absorption and circular dichroism spectra of five different monosaccharide pentaacetates were measured. These spectra were found to be dominated by the contributions from the acetate groups. In the carbonyl region, α- and β-d-glucose pentaacetates do not show measurable vibrational circular dichroism (VCD), but α- and β-d-galactose pentaacetates and α-d-mannose pentaacetate show significant VCD, with mannose pentaacetate giving opposite signs to those of α- and β-d-galactose pentaacetates. These observed features are interpreted to reflect the orientation of carbonyl groups around the carbohydrate ring.