The designedphotolabelingprobes: 5-diazonium-1-β-D-ribofuranosyl-1H-imidazole-4-carboxamide (1) and 5-azido-1-β-D-ribofuranosyl-1H-imidazole-4-carboxamide (2) were synthesized via a short and convenient synthetic route,namely by diazotizing AICAR and subsequently performing substitution with NaN 3 . Although 1 was not stable even at low temperatures, 2 showed a rapid and clean photochemical reaction
Diazotization of 5-amino-N'-methoxy-1-methylimidazole-4-carboxamidine (4a) with NaNO2 in 1N aqueous HCl was found to give the 1-methoxy-2-azaadenine derivative 8a·HI, which produced 5-azido-1-methylimidazole-4-carbonitrile (5a) on treatment with aqueous Na2CO3. The ribosyl analogue 5b, obtained from the riboside 4b by similar diazotization, was utilized for the synthesis of 5-azido-1-β-D-ribofuranosylimidazole-4-carboxamide (9b), a novel AICA riboside analogue. On heating in HCONMe2 at 70°C for 10min, 8a·HI yielded the 1-N-oxide 7a. Several reactions to transform the functional groups in 5a were also investigated.
order to study the mechanisms responsible for their antiviraleffects using a photolabeling approach, we have developed photolabelingprobes of ribavirin and EICAR, in which an azido group was introduced into the pseudobases of triazole and imidazole, respectively. The ribavirin photoprobes were obtained by directly coupling the azidotriazole to the protected ribose sugar, while the EICAR probe was prepared