Stereocontrolled Synthesis of Dithymidine Phosphorothioates by Use of a Functionalized 5′- Protecting Group Bearing an Imidazole Residue

Diastereoselective formation of internucleotidic phosphorothioate triester bonds was achieved by use of 3-(imidazol-1-ylmethyl)-4′,4″-dimethoxytrityl (IDTr) as a 5′-hydroxyl protecting group in the phosphotriester approach. After removal of all the protecting groups, stereochemistry of the major product was determined as the Spconfiguration by enzymatic digestion. This paper is dedicated to the memory of the late Professor Tsujiaki Hata.