Synthesis of ribonucleoside 3′,5′‐cyclic phosphorothioates using a modified hydroxybenzotriazole phosphotriester approach

Abstract
Phosphorothioylation of 3′,5′‐dihydroxyl ribonucleosides with O‐(2‐chlorophenyl) O, O‐bis[6‐(trifluoromethyl)‐1‐benzotriazolyl] phosphorothioate, followed by addition of N‐methyl‐imidazole and removal of protecting groups, gives ribonucleosides 3′,5′‐cyclic phosphorothioates. The latter compounds could also be prepared by phosphorothioylation of 2′,3′,5′‐trihydroxyl ribonucleosides.