Preparation of an Octadeoxyribonucleoside Heptaphosphorothioate by the Phosphotriester Approach in Solution†

Abstract

The synthesis of the octadeoxyribonucleoside heptaphosphorothioate, d[Tp(s)Tp(s)Gp(s)Gp(s)Gp(s)Gp(s)Tp(s)T] by the phosphotriester approach in solution is described. The phosphorothioate internucleotide linkages are protected by the S-(2-cyanoethyl) group and 1-(mesitylene-2-sulfonyl)-3-nitro-1,2,4-1H-triazole (MSNT) is used as the coupling agent. A block synthesis strategy (2 + 2 → 4 and 4 + 4 → 8) is followed. This article is dedicated to the memory of Professor Tsujiaki Hata