3-DEAZAGUANINE N-7-(2'-DEOXY-BETA-D-RIBOFURANOSIDES) AND N-9-(2'-DEOXY-BETA-D-RIBOFURANOSIDES) - BUILDING-BLOCKS FOR SOLID-PHASE SYNTHESIS AND INCORPORATION INTO OLIGODEOXYRIBONUCLEOTIDES

Abstract

Oligonucleotides containing 3-deaza-2'-deoxyguanosine (1) or its N7-regioisomer 2 were prepared by solid-phase synthesis using P(III) chemistry. Protection of 1 or 2 with N,N-dimethylformamide diethyl acetal followed by 4,4'-dimethoxytritylation afforded imidazo[4,5-c]pyridines 10b and 11b, respectively. The latter were converted into the 3'-phosphonates 10c or 11c, respectively; the cyanoethyl N,N-diisopropylphosphoramidite 10d was also prepared. The oligonucleotide building blocks were employed in automated solid-phase synthesis. The self-complementary oligomers 13, 15, and 17 were prepared and characterized by enzymatic hydrolysis with snake-venom phosphodiesterase followed by alkaline phosphatase. There CD spectra exhibited the general structure of a B-DNA.