Efficient RNA-targeting by the introduction of aromatic stacking in the duplex major groove via 5-(1-phenyl-1,2,3-triazol-4-yl)-2'-deoxyuridines.

Three pyrimidine nucleosides with differently substituted phenyltriazoles attached to the 5-position were prepared by Cu(I)-assisted azide-alkyne cycloadditions (CuAAC) and incorporated into oligonucleotides. Efficient π-π-stacking between two or more phenyltriazoles in the major groove was found to increase the thermal stability of a DNA:RNA duplex significantly. The best stacking, and most stable duplex, was obtained by a sulfonamide substituted derivative.