DNA triplex structures are stabilized by the incorporation of 3′-endo blocked pyrimidine nucleosides in the hoogsteen strand

A short route to pyrimidine locked nucleosides has been developed for their incorporation in triplex forming oligonucleotides (TFO). Compared to oligonucleotides build with standard nucleosides, the modified TFOs containing 3′-endo blocked residues formed, with their corresponding DNA duplexes, more stable triple helix systems, an effect which might be ascribed to the 3′-endo pucker of the modified nucleoside residues.