Novel route to oligo(deoxyribonucleoside phosphorothioates). Stereocontrolled synthesis of P-chiral oligo(deoxyribonucleoside phosphorothioates).

The synthesis and separation of diastereoisomerically pure 5'-O-DMT-nucleoside 3'-O-(2-thio-1,3,2-oxathiaphospholane) allows their use as synthons in DBU-catalyzed reaction with the 5'-hydroxyl function of solid-support-bound nucleoside moiety. Since this reaction is stereospecific (greater than 99%), this novel method allows preparation of oligo(nucleoside phosphorothioates) with predetermined chirality at each P-chiral internucleotide phosphorothioate centre.