Purines, pyrimidines, and imidazoles. Part 51. New syntheses of some 5-alkyl- and 5-dialkyl-aminoimidazoles. 3-Alkylimidazolium nucleosides and 3-alkylpurines

Ethyl 3-methyl-5-amino-1-(2,3-O-isopropylidene-α- and -β-D-ribofuranosyl)imidazolium-4-carboxylate iodides, the corresponding benzyl-β-D-ribofuranosyl ester, and benzyl 3-methyl-5-amino-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)imidazolium-4-carboxylate iodide have been prepared by methylation of the corresponding nucleosides with methyl iodide. Their reactions with acids and bases have been examined. Ethyl 4(5)-methylamino- and dimethylamino-imidazole-5(4)-carboxylates have been prepared in a sequence of reactions from ethyl cyanoacetate and the former compound was converted into 3-methylhypoxanthine by heating with formamidine acetate and into 3-methylguanine by a sequence of reactions. The methylamino-derivative undergoes a Dimroth rearrangement when heated with aqueous ammonia, to produce 1-methyl-5-aminoimidazole-4-carboxamide.