New strategies for the synthesis of unmodified and modified oligonucleotides

Abstract

In this paper, our recent studies on the synthesis of unmodified and modified oligonucleotides are comprehensively reviewed. We have developed a new synthetic strategy using TrS, a new 5'-protecting group, that enabled us to reduce one of the steps previously required for DNA synthesis. The "activated phosphite method" without base protection could provide a new tool for the synthesis of DNA oligomers involving base-labile functional groups such as N-acylated nucleobases capable of Watson-Crick base pairing. This new method was successfully applied to the synthesis of oligodeoxynucleotides incorporating cytosine N-oxide or adenine N-oxide that could not be synthesized by the current methods. Furthermore, several approaches we recently developed for the synthesis of several kinds of 2'-O-modified RNA oligomers will be reported.