A new, but old, nucleoside analog: The first synthesis of 1-deaza-2′-deoxyguanosine and its properties as a nucleoside and as oligodeoxynucleotides

Abstract

The first synthesis of 5-amino-3-(2′-deoxy-β-D-ribofuranosyl imidazo[4,5-b]pyridin-7-one (1-deaza-2′-deoxyguanosine) is described. The compound was converted from the known AICA-deoxyriboside. The tautomeric structure of the base moiety was determined by theoretical calculation to be a hydroxyl form. Although the analog was found to be labile to acidic conditions, 1-deaza-2′-deoxyguanosine was successfully converted into a phosphoramidite derivative, which was incorporated into oligodeoxynucleotides by the standard phosphoramidite method. Thermal stabilities of oligodeoxynucleotides containing 1-deaza-2′-deoxyguanosine were investigated by thermal denaturing experiments. Also, a triphosphate analog of 1-deaza-2′-deoxyguanosine was synthesized for polymerase extension reactions. Single nucleotide insertion reactions using a template containing 1-deaza-2′-deoxyguanosine, as well as 1-deaza-2′-deoxyguanosine triphosphate, were performed using the Klenow fragment (exonuclease minus) polymerase and other polymerases. No hydrogen bonded base pairs, even a 1-deaza-2′-deoxyguanosine:cytidine base pair, were indicated by thermal denaturing studies. However, though less selective and less effective than the natural guanosine counterpart, the polymerase extension reactions suggested the formation of a base pair of 1-deaza-2′-deoxyguanosine with cytidine during the insertion reactions.