The Conformation of β-Pseudouridine about the Glycosidic Bond as Studied by 1 H Homonuclear Overhauser Measurements and Molecular Orbital Calculations

Abstract

The conformation of β-pseudouridine about the glycosidic bond has been studied by both the internal nuclear Overhauser effect and CNDO molecular orbital calculations. Both syn and anti conformations are found to exist in rapid equilibrium, with roughly equal populations of each. The proportion of syn to anti conformations does not change significantly with pD over the range 7.1 to 11.6. The CNDO calculations suggest that the syn conformation is stabilized by formation of a hydrogen bond, C 4 =O … O—H 5′ , but the n.m.r. data indicate that if such a bond exists its probability is the same at pD 7.1 and 11.6. Major contributions to n.O.e. may occur through conformations other than those which are most stable.