Synthesis of 4-Thiopseudoisocytidine and 4-Thiopseudouridine as Components of Triplex-forming Oligonucleotides

In this paper, we report convenient methods for the synthesis of 4-thiopseudoisocytidine (s 4 ψiC) and 4-thiopseudouridine (s 4 Ψ), 1 HNMR spectral analysis of these modified nucleosides showed that both s 4 Ψ and s 4 ψiC prefer C3'-endo ribose puckering. These conformational properties are favorable for the stabilization of triplex formation.