Synthesis and evaluation of oligonucleotides incorporating novel artificial nucleobases for the selective formation of non-natural type triplexes.

Regulation of specific gene expression by the sequence specific triplex formation has been expected as a new biological tool or a new therapeutic method in the so-called antigene strategy. As native nucleobases form triplexes only within homopurine-homopyrimidine duplexes, expansion of the target sequences to general ones has been desired. We have previously reported the selective formation of base triplets by the non-native nucleobases (1, 2) with a CG or a TA base pair, respectively, in the organic solvent. In this paper, we wish to report the synthesis of the new non-native bases (3, 4, 9-11) and their incorporation into the triplex-forming oligonucleotides (TFOs), as well as their ability of triplex formation.