A new and efficient route to the synthesis of pyrazole and pyrimidine C- nucleoside derivatives

Article abstract of DOI:10.1016/S0040-4039(98)00631-5

A new route to the synthesis of pyrazole and pyrimidine C-nucleosides, involving as the key step a metal catalysed reaction of β-D-ribofuranosyl ketoesters with alkyl cyanoformates, is described. 2,3,5-Tri-O-benzoyl-β-D- ribofuranosyl cyanide (1) reacts with α-bromoesters, in the presence of zinc dust, to give β-D-ribofuranosyl-enaminoesters 2 which are easily hydrolised to β-ketoesters 3. The reactions of compounds 3 with alkyl cyanoformates, in the presence of catalytic amounts of [Cu(acac)2], afford C-glycosyl enaminoketosters 4. These compounds react with benzylhydrazine and acetamidine to give pyrazole and pyrimidine C-nucleosides 5 and 6 respectively.