Pseudorotation of the ribofuranose ring. A theoretical study and a comparison with nuclear magnetic resonance results

Abstract

The results of energy calculations by means of the consistent force field method performed for methyl β-D-ribofuranoside are presented. Two regions of stable pentose conformations are predicted, other than those observed for the ribose moiety in most nucleosides. Local energy minima are associated with different conformations of the hydroxy and hydroxymethylene groups. Models of the molecule in solution are proposed, for which proton coupling constants are calculated; a satisfactory agreement with experimental ¹H n.m.r. coupling constants is achieved. The influence of the exocyclic substituents and of the orientation of the hydroxy groups on the conformation of the furanose ring and on its interconversion by pseudorotation is discussed.