Development of novel C-nucleoside analogues for formation of antiparallel-type triplex DNA with duplex DNA that includes TA and dUA base pairs

Expansion of the triplex DNA forming sequence is required in the genomic targeting fields. Basically, the triplex DNA is formed by the interaction between the triplex-forming oligonucleotides and homo-purine region with the target duplex DNA. The presence of the base pair conversion sites is hampered by the stable triplex formations. To overcome this limitation, it is necessary to develop an artificial nucleic acid to recognize the base conversion sites, the CG and the TA base pairs. We now describe the synthesis of the C-nucleoside analogues and an evaluation of the ability of the triplex formations. Consequently, the combined use of the novel C-nucleoside analogues, AY- AY-d(Y-NH2), AY-d(Y-Cl) and IAP-d(Y-Cl), is capable of recognizing the duplex DNA including the TA or the dUA base pair.