Synthesis and triplex-forming properties of 2',4'-BNA derivatives bearing pyridines as an unnatural nucleobase.

Triplex-forming oligonucleotide (TFO) could serve as a potential tool to regulate gene expression. However, stability of the triplex is relatively low, and the sequence of the target dsDNA is severely regulated. In an attempt to overcome these problems, we have designed and synthesized 2',4'-BNA monomers bearing a 6-aminopyridin-3-yl (aPy(B)) and pyridin-2-yl group (Py(B)) as a nucleobase. These monomers were successfully incorporated into natural TFOs, and the triplex-forming property of the modified TFOs was evaluated by UV melting experiments.