SYNTHESIS OF OLIGONUCLEOTIDES CONTAINING 7-(2-DEOXY-BETA-D-ERYTHRO-PENTOFURANOSYL)GUANINE AND 8-AMINO-2'-DEOXYGUANOSINE

The synthesis of oligonucleotides containing 7-(2-deoxy-beta-D-erythro -pentofuranosyl)guanine and 8-amino-2'-deoxyguanosine was accomplished . The viable intermediate l-7-(2-deoxy-beta-D-erythro-pentofuranosyl)g uanine (6) was prepared via a four step deoxygenation procedure from 7 -beta-D-ribofuranosylguanine (1). The 5'-hydroxyl group of 6 was prote cted as 4,4'-dimethoxytrityl ether and then converted to the target ph osphoramidite (8) via conventional phosphitylation procedure. The amin o groups of 8-amino-2'-deoxyguanosine (9) were protected in the form o f N-(dimethylamino)methylene functions to give the protected nucleosid e 10, which was subsequently converted to the target phosphoramidite 1 2 via dimethoxytritylation followed by phosphitylation. The phosphormi dites 8 and 12 were incorporated into a 26-mer and a 31-mer G-rich oli gonucleotide using solid-support, phosphoramidite methodology. Analysi s of antiparallel triplex formation by the oligonucleotides containing 7-(2-deoxy-beta-D-erythro-pentofuranosyl)guanine in place of 2'-deoxy guanosine showed no enhancement in triple helix formation.