VACUUM-ULTRAVIOLET CIRCULAR-DICHROISM STUDIES OF SIMPLE SACCHARIDES

The circular dichroism (CD) of simple sugars was extended to 140 nm us ing film samples. The 150-190-nm region can be decomposed into four co mponents. The signs of these four components are strictly correlated w ith anomeric configuration. Dominant contributions to CD arise from el ectronic transitions localized on the oxygen atoms of the ether chromo phores. The CD below 150 nm represents the onset of the lowest energy sigma-sigma transition, the sign of which is also correlated with ano meric configuration. By extrapolation, its center is estimated to be a t approximately 120-130 nm. The CD spectra of representative disacchar ides contain a conformation-dependent contribution,indicating the usef ulness of CD as a conformational probe. The results reported here prov ide a basis for developing improved interpretive models.