DNA tripler 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 tripler forming oligonucleotides (TFO). Compared to oligonucleotides built 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. (C) 2000 Elsevier Science Ltd. All rights reserved.