Iterative synthesis of nucleoside oligophosphates with phosphoramidites.

P-Amidites can be used in iterative couplings to selectively give mixed P(III) -P(V) anhydrides. These intermediates can be oxidized followed by a rapid removal of the two terminal fluorenylmethyl groups. An iterative synthesis (coupling, oxidation, deprotection) of nucleoside oligophosphates can be carried out in solution and on a solid support. The coupling rates and yields are high, the procedures convenient (non-dry reagents and solvents, ambient conditions, unprotected nucleotides), and the purification is very simple. The method works with all canonical nucleosides and holds promise for significant simplification of the usually cumbersome process of P-anhydride bond construction.