Synthesis and triplex-forming properties of oligonucleotides containing thio-substituted C-nucleoside 4-thiopseudoisocytidine

We synthesized the 3′-phosphoramidite building block of 4-thiopseudoisocytidine (s4ΨiC) and incorporated it into triplex-forming oligonucleotides (TFOs). The results of thermal denaturation of triplexes incorporating s4ΨiC showed that s4ΨiC could be used as a nucleoside component of TFOs to increase the thermal stability of triplexes at pH 7.