98. Studies on the Base-Pairing Properties of N7-(2-Deoxy-β-D-erythro-pentofuranosyl)guanine (N7Gd)

Article abstract of DOI:10.1002/hlca.19970800424

The base-pairing properties of N⁷-(2-deoxy-β-D-erythro-pentofuranosyl)guanine (N⁷G_d; 1) are investigated. The nucleoside 1 was obtained by nucleobase-anion glycosylation. The glycosylation reaction of various 6-alkoxypurin-2-amines 3a-i with 2-deoxy-3,5-di-O-(4-toluoyl)-α-D-erythro-pentofuranosyl chloride (8) was studied. The N⁹/N⁷-glycosylation ratio was found to be 1:1 when 6-isopropoxypurin-2-amine (3d) was used, whereas 6-(2-melhoxyethoxy)purin-2-amine (3i) gave mainly the N⁹-nucleoside (2:1). Oligonucleotides containing compound 1 were prepared by solid-phase synthesis and hybridized with complementary strands having the four conventional nucleosides located opposite to N⁷G_d. According to T_m values and enthalpy data of duplex formation, a base pair between N⁷G_d and dG is suggested. From the possible N⁷G_d · dG base pair motives, Hoogsteen pairing can be excluded as 7-deaza-2′-deoxyguanosine forms the same stable base pair with N⁷G_d as dG.