Studies on new routes for the synthesis of 4- and 5-aminoimidazole nucleoside derivatives

The synthesis of urethane protected 4- and 5-aminoimidazole nucleoside derivatives 4 and 9 by two different routes is described. These routes are transformation of the carboxylate substituted imidazole nucleoside 1 via a Curtius rearrangement to give 4 and direct ribosylation of the imidazole base 6 to give a mixture of positional isomers 7 and 8 , which by deacetylation afford 4 and 9 , respectively. The convenience of each route depended on the positional isomer to be synthesized.