Synthesis of 1,2,3-triazole nucleosides via the acid-catalyzed fusion procedure

The acid-catalyzed fusion of methyl 1,2,3-triazole-4-carboxylate, 4-cyano-1,2,3-triazole, and 4-nitro-1,2,3-triazole with an acylated ribofuranose provided the corresponding 2-β-D-ribo-furanosyl-4-substituted-1,2,3-triazoles along with the isomeric 1-β-D-ribofuranosyl-4-substituted-1,2,3-triazoles. The structures of these nucleosides were assigned on the basis of their nmr spectra. The synthesis of 2-β-D-ribofuranosyl-1,2,3-triazole-4-carboxamide from both the corresponding methyl ester and cyano nucleosides is described. The cyano nucleosides were utilized to prepare 2-β-D-ribofuranosyl-1,2,3-triazole-4-thiocarboxa?ide and 1-β-D-ribofuranosyl-1,2,3-triazole-4-thiocarboxamide. Reduction of the 4-nitro-1,2,3-triazole nucleosides provided 4-amino-2-β-D-ribofuranosyl-1,2,3-triazole and the isomeric 4-amino-1-β-D-ribofuranosyl-1,2,3-triazole. The acid-catalyzed fusion procedure with 1,2,3-triazole afforded 1-β-D-ribofuranosyl-1,2,3-triazole and 2-β-D-ribofuranosyl-1,2,3-triazole.