Abstract
The conformations of two phosphodiester-linked dinucleotides and their analogues containing a 3′-S-phosphorothiolate linkage were investigated using 1H NMR spectroscopy. The phosphorus decoupled 1H NMR spectrum of each compound was simulated and values for the vicinal proton–proton coupling constants of the sugar ring hydrogens abstracted at several different temperatures, for use in full conformational analyses. The UV absorbance temperature profiles of the dimers were also analysed. It was found that in both the deoxyribo and ribo analogues the sugar ring conformations are affected by the phosphorothiolate modification, with a large increase in the percentage of north-type puckering. This change is mainly due to the decrease in the influence of the gauche effect between the 3′-substituent and the O4′-ring oxygen experienced when substituting an oxygen atom for the less electronegative sulphur atom. Copyright © 1999 John Wiley & Sons, Ltd.
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