Phosphorylation Within DNA Duplexes. Synthesis of Modified Oligodeoxyribonucleotide

Abstract

An effective method was suggested for the activation of phos-phomonoester groups in nicks of a double-strand DNA (1,2). This approach allows to incorporate various sugar phosphate backbone modifications at a particular site when DNA duplexes are being assembled. A modifying group is first introduced at the 5′- or 3′-termini of oligonucleotides, then a duplex is formed and oligomers are coupled on the complementary template using water-soluble l-ethyl-3-(3-dimethyl-aminopropyl)carbodiimide or cyanogen bromide as the condensing agents. Various DNA duplexes containing not only natural phosphodiester but also phosphoramidate and pyrophospha-te internucleotide bonds, as well as phosphodiester bonds between nucleotide residues with modified sugar analogs (ribo-, arabino- and xylo-derivatives) were assembled by this method.