Selective synthesis of phosphate monoesters by dehydrative condensation of phosphoric acid and alcohols promoted by nucleophilic bases.

Phosphate monoesters are synthesized from a mixture of phosphoric acid (1 or 2 equiv) and alcohols (1 equiv) in the presence of tributylamine. The reaction is promoted by nucleophilic bases such as N-alkylimidazole and 4-(N,N-dialkylamino)pyridine. 2',3'-O-Isopropylidene ribonucleosides are selectively converted to their 5'-monophosphates without the protection of amino groups in nucleobases.