Synthesis of a ³⁵S‐labeled dinucleoside phosphorothioate prodrug, an orally bioavailable anti‐HBV agent

The 35 S‐labeled, dinucleoside phosphorothioate 1, an orally available agent against hepatitis B virus, was prepared in eight steps with high specific activity and radiochemical purity. Radiolabeled 3 H ‐benzodithiole‐3‐one‐1,1‐dioxide was synthesized in four steps from 35 S 8 and was used as the sulfurizing reagent.