F. Seela et P. Leonard, N-7-DNA - SYNTHESIS AND BASE-PAIRING OF OLIGONUCLEOTIDES CONTAINING N-7-(2-DEOXY-BETA-D-ERYTHRO-PENTOFURANOSYL)GUANINE (N(7)G(D)), Helvetica Chimica Acta, 79(2), 1996, pp. 477-487
The synthesis of oligonucleotides containing N-7-(2-deoxy-beta-D-eryth
ro-pentofuranosyl)guanine (N(7)G(d); 1) is described. Compound 1 was p
repared by nucleobase-anion glycosylation of 2-amino-6-methoxypurine (
5) with -3,5-di-O-(toluoyl)-alpha-D-erythro-pentofuranosyl chloride (6
) followed by detoluoylation and displacement of the MeO group (8-->10
-->1). Upon base protection with the (dimethylamino)methylidene residu
e (-->11) the 4,4-dimethoxytrityl group was introduced at OH--C(5')(--
>12). The phosphonate 3 and the phosphoramidite 4 were prepared and us
ed in solid-phase oligonucleotide synthesis. The self-complementary do
decamer d(N(7)G-C)(6) shows sigmoidal melting. The T-m of the duplex i
s 40 degrees. This demonstrates that guanine residues linked via N(7)
of purine to the phosphodiester backbone are able to undergo base pair
ing with cytosine.