2,4-Dinitrophenol: a novel activating reagent in nucleotide synthesis via the phosphoramidite route. Design of new effective phosphitylating reagents

2,4-Dinitrophenol (DNP) is a remarkably efficient activator in the reaction of P(III) amides with nucleosides to give P(III) esters in excellent yield. Typical examples of this novel procedure are presented herein. Mechanistic features of the activation were elucidated by model studies of the reaction of bis(2-cyanoethyl)diisopropylphosphoroamidite with benzyl alcohol. The importance of the initial protonation stage and formation of an intermediate P(III)-2,4-dinitrophenyl ester were clearly demonstrated by 31P NMR spectroscopy and independent synthesis. New phosphitylating reagents containing the 2,4-dinitrophenoxy group do not require any activation.