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

Abstract

Oligonucleotides containing N-7-(2'-deoxy-beta-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-droxy-3,5-di-O-(4-toluoyl)-alpha-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 Cd base pairs are more stable in the case of parallel strand orientation than in the case of antiparallel chains.