Synthesis and duplex stability of oligonucleotides containing 7-vinyl-7-deazaguanine as a strong electron-donating nucleobase

We synthesized 7-vinyl-7-deazaguanine (vzG), an N7-modified guanine base, which has a smaller oxidation potential than G and 7-deazaG. The incorporation of vzG into oligonucleotides was achieved by phosphoramidite chemistry on a DNA synthesizer. The Tm of the duplex containing vzG was higher than that of the corresponding duplex containing G or 7-deazaG. The stabilization of the duplex containing vzG is due to the favorable enthalpy change by increased π-stacking between the vinyl group and the 5′-flanking base.