Synthesis of 4-nitrophenyl esters of thymidine 3′-phosphate and 3′-phosphorothioate using a new phosphorylating agent

2′-Deoxynucleoside-3′-O-(4-nitrophenyl) phosphoranilidates (e.g., 2), prepared by the action of O-(4-nitrophenyl)N-phenylphosporamidochloridate (1) on alcohols, are converted into the corresponding 4-nitrophenyl phosphate esters (e.g., 3) or P-chiral 4-nitrophenyl phosphorothioate esters (e.g., 4) by treatment with NaH–CX2(X = O or S).