N 7-DNA: Base-pairing properties of N 7-(2'-deoxy-β-d-erythro- pentofuranosyl)-substituted adenine, hypoxanthine, and guanine in duplexes with parallel chain orientation

Abstract

Oligonucleotides containing N 7-(2'-deoxy-β-D-erythro- pentofuranosyl)adenine (1), -hypoxanthine (2), and -guanine (3) were synthesized on solid-phase using phosphonate and phosphoramidite chemistry. As part of the synthesis of compound 2, the nucleobase-anion glycosylation of various 6-alkoxypurines with 2-deoxy-3,5-di-O-(4-toluoyl)-α-D-erythro- pentofuranosyl chloride (5) was investigated. The duplex stability of oligonucleotides containing N 7-glycosylated purines opposite to regular pyrimidines was determined, and thermodynamic data were calculated from melting profiles. Oligodeoxyribonucleotide duplexes containing N 7- glycosylated adenine. T(d) or N 7-glycosylated guanine C(d) base pairs are more stable in the case of parallel strand orientation than in the case of antiparallel chains.