N7-DNA: Synthesis and base pairing of oligonucleotides containing N7-(2-deoxy-β-D-erythro-pentofuranosyl)guanine (N7G(d))

Article abstract of DOI:10.1002/hlca.19960790215

The synthesis of oligonucleotides containing N⁷-(2-deoxy-β-D-erythro-pentofuranosyl)guanine (N⁷G(d); 1) is described. Compound 1 was prepared by nucleobase-anion glycosylation of 2-amino-6-methoxypurine (5) with 2-deoxy-3,5-di-O-(4-toluoyl)-α-D-erythro-pentofuranosyl chloride (6) followed by detoluoylation and displacement of the MeO group (8 → 10 → 1). Upon base protection with the (dimethylamino)methylidene residue (→ 11) the 4,4-dimethoxytrityl group was introduced at OH-C(5') (→ 12). The phosphonate 3 and the phosphoramidite 4 were prepared and used in solid-phase oligonucleotide synthesis. The self-complementary dodecamer d(N⁷G-C)₆ shows sigmoidal melting. The T(m) of the duplex is 40°. This demonstrates that guanine residues linked via N(7) of purine to the phosphodiester backbone are able to undergo base pairing with cytosine.