Recognition of T·A interruption by 2′,4′-BNAs bearing heteroaromatic nucleobases through parallel motif triplex formation

2′-O,4′-C-methylene bridged nucleic acid (2′,4′-BNA) monomers bearing novel unnatural nucleobases, 4-(3-benzamidophenyl)-2-pyridone and 2-(N-methylbenzamido)thiazole, were synthesized and successfully incorporated into oligonucleotides. UV melting experiments showed that the corresponding oligonucleotide derivatives formed stable triplexes with dsDNA targets even in the presence of a T·A interruption.