Abstract: | Synthesis and stereochemical characterization of enantiomerically pure nucleoside-3′-phosphorothioate esters and salts are reported. Vicinal carbon–phosphorus couplings reflect different predominance of the ? conformation in the isomeric (Rp and Sp) esters, while for the salts the ?t conformation prevails in both stereoisomers. The influence of solvent and temperature on the conformational preferences is also described. |