Determination of the syn‐anti Equilibrium of Some Purine 3′:5′‐Nucleotides by Nuclear‐Magnetic‐Relaxation Perturbation in the Presence of a Lanthanide‐Ion Probe

Abstract

The aqueous solution conformation of four purine 3′:5′‐nucleotides varying in their substituents at C‐6 and C‐8 has been studied using gadolinium(III) to perturb the proton relaxation times. The ribose conformations are inferred. All the nucleotides are best described as being in a dynamic equilibrium between syn and anti conformations and the position of this equilibrium is not dramatically affected by changing the substituent at C‐6. These nucleotides in their neutral base form slightly favour an anti conformation. In the presence of a bulky methylthio group at C‐8 the equilibrium is shifted towards a dominance from the syn conformation due to steric repulsion factors. Copyright © 1977, Wiley Blackwell. All rights reserved