Conformation of nucleosides: Circular dichroism study of solvent effect on the syn-anti conformational equilibrium of pyrimidine nucleosides

Abstract

Circular dichroism spectra of uridine derivatives were measured in various solvents. Miles' diagram (Miles, D.W., Robins, M.J., Robins, R.K., Winkley, M.W. and Eyring, H. (1969) J. Am. Chem. Soc. 91, 831–838) was qualitatively confirmed and the important role of the 5′-OH group in the stabilization of the syn conformer was established. An analysis of crystallographic data indicates that the furanose ring constrained by an additional dioxolane ring assumes the envelope conformation. For this type of sugar puckering the syn and anti conformations are energetically equal. The conformation of 3′,5′- and 2′,3′-cyclophosphates is discussed in terms of the results obtained for model compounds.