The C-8-(2 `-deoxy-beta-D-ribofuranoside) of 7-deazaguanine: Synthesis and base pairing of oligonucleotides with unusually linked nucleobases

Abstract

The 7-deazaguanine (2-aminopyrrolo [2,3-d]pyrimidin-4-one) C-8-(2'-deoxy-beta -D-ribofuranoside) (6b), which possesses an unusual glycosylation site, was synthesized and incorporated in oligonucleotides. The oligonucleotides were prepared by solid-phase synthesis using phosphoramidite chemistry and were hybridized to form duplex DNA. Compound 6b is able to form base pairs with 2'-deoxy-5-methylisocytidine (m(5)isoC(d)) in oligonucleotide duplexes with antiparallel chain orientation and with dC in parallel duplex DNA. Thus, the CB-nucleoside 6b shows a similar base recognition as 2'-deoxyisoguanosine but not as 2'-deoxyguanosine. This indicates that the nucleic acid recognition not only depends on the donor-acceptor pattern of the nucleobase but is influenced by the glycosylation site. Base pairs of compound 6b formed with canonical and modified nucleosides are proposed.