Synthesis of new 3,7,9-trisubstituted pyrazolo[4,3-e][1,2,4]triazolo[4,3-c] pyrimidines acyclo C-nucleosides via oxidative cyclisation

Condensation of 4-hydrazino-1,3-diphenylpyrazolo[3,4-d]-pyrimidine with the aldohexoses, namely, D-glucose, D-galactose, D-rnannose and the aldopentoses, D-arabinose, D-xylose and D-ribose, by heating in an aqueous ethanol in the presence of a catalytic amount of HCI, gave the respective aldehydo-sugar hydrazones. Oxidative cyclisation of such hydrazones by stirring with iron(III) chloride in ethanol at room temperature afforded the expected acyclo C-nucleosides 3-substituted-7,9-diphenylpyrazolo[4,3-e][1,2,4]triazolo[4,3-c]-pyrimidines. The structures of the cyclised sugar hydrazones were confirmed by their elemental analyses and spectral data.