Studies of Nucleosides and Nucleotides. XLIX. Synthesis of 8-Fluoroadenosine

In order to obtain 8-fluoroadenosine, 8-aminoadenosine was subjected to Schiemann reaction. However, presumably due to lability of the nucleosidic linkage of 8-fluoroadenosine, only 8-fluoroadenine and 8-oxyadenine were obtained as the product. When 2', 3', 5'-tri-O-acetyl-8-aminoadenosine, which was synthesized from 2', 3', 5'-tri-O-acetyl-8-bromoadenosine by way of 8-azido compound, was diazotized with sodium nitrite in 40% HBF4 at -20°, 2', 3', 5'-tri-O-acetyl-8-fluoroadenosine was obtained in yield around 10%. Optical properties and migratory behaviors in paper chromatography resembled those of 8-bromoadenosine derivative. 8-Fluoroinosine and 8-oxyadenine were also obtained as the byproduct. Deacetylation of triacetyl-8-fluoroadenosine gave 8-fluoroadenosine, which had circular dichroism (CD) profile similar to that of 8-bromoadenosine and a syn conformation was suggested to this compound. 8-Aminoguanosine gave 8-aminoxanthine and 8-fluoroxanthine by the Schiemann reaction.