Base-pairing properties of 8-aza-7-deazaadenine linked via the 8-position to the DNA backbone

Abstract

The base-pairing properties of oligonucleotides containing the unusual N-8-linked 8-aza-7-deazaadenine 2'-deoxyribonucleoside (2a) as well as its 7-bromo derivative 2b are described. The oligonucleotides were prepared by solid-phase synthesis employing phosphoramidite chemistry. Compound 2a forms a strong base pair with T-d for which a reverse Watson-Crick pair is suggested (Fig. 9). Compound 2a displays a lower N-glycosylic-bond stability than its Ng-nucleoside and shows strong stacking interactions when incorporated into oligonucleotides. The replacement of 2'-deoxyadenosine by 2a does not significantly influence the duplex stability. However, this behavior depends on the position of the incorporation.