AN ENERGETIC CORRELATION OF AB INITIO AND NMR STUDIES OF THE 3′-GAUCHE EFFECT IN 3′-SUBSTITUTED THYMIDINES

Abstract

A straightforward correlation of our experimental NMR findings on 3′-substituted thymidine derivatives with that of the ab initio calculations shows that (i) the ΔG of N ← S equilibrium in nucleoside can be predicted from the ab initio calculated ΔE _S-N obtained from 6-311++G^** level of theory; (ii) the substituent-dependent steric and stereoelectronic effects on the bias of the two-state N ← S equilibrium in nucleosides can also be predicted from the ab initio calculations with sufficiently large basis functions, and (iii) the necessity of mimicking the solvation behaviour of the experimental NMR measurement condition in the ab initio calculations of biomolecules is also emphasized.

ACKNOWLEDGEMENTS

We thank the Swedish Board for Technical Development (TFR), the Swedish Natural Science Research Council (NFR), and the Swedish Board for Technical Development (NUTEK) for generous financial support. Thanks are due to the Wallenbergstiftelsen, ForskningsraÊ dsnämnden and the University of Uppsala for funds to purchase of 500-MHz and 600-MHz Bruker DRX NMR spectrometers.