C-Nucleosides and related compounds. VII. Synthesis of carbocyclic analogues of C-nucleosides

Condensation of lactone 1 and aminoguanadine provides the amino-triazole carbocyclic analogue of C-nucleoside 2a. Lead tetraacetate oxidation of the semicarbazone derivative 4 leads to the amino-oxadiazole derivative 5. Isoxazolines 11 and 12 are obtained by 1,3-dipolar addition of mesitonitrile oxide with the α,β-unsaturated ester 13. Addition of diazomethane onto ester 13 gives the pyrazoline 16 which can be oxidized with bromine to the corresponding carboethoxy-pyrazole 17. The latter is converted to the carboxamido-pyrazole 18 by treatment with ammonia.