Synthesis of ppTppp via phosphotriester intermediates

The bifunctional and crystalline phosphorylating agent morpholino-0,0-bis[1-benzotriazolyl]phosphate has been used for the preparation of a 3',5'-bis-phosphotriester intermediate of thymidine. The latter has been converted into ppTppp by the following consecutive steps; removal of the benzotriazolyl group followed by the addition of phosphoric acid and removal of the 2-(4-nitrophenyl)-ethyl group followed by the addition of pyrophosphoric acid.