Novel unique activating reagents in synthesis of biophosphates via phosphoroamidite route

Trimethylhalogenosilanes Me3SiX (X=Cl,Br) are remarkably efficient activato rs in the reaction of P(III) amidites with nucleosides and other alcohols o f biological interest to give P(III) esters in excellent yield. This activa tion is illustrated by synthesis of P(III) compounds containing a phosphoru s-fluorine bond. Under specially chosen conditions the interaction between trimethylhalogenosilanes, 2'-deoxy-nucleosidylphosphoroamidites and nucleos ides allows synthesis of 5'-phosphonate-linked deoxydinucleotides. 2,4-Dini trophenol is an effective activator in "amidite" coupling.