Diazole C-Nucleosides

Like azole C-nucleosides (Section VI), 1,2-diazole C-nucleosides and their analogs were also extensively studied from both the academic and the applied and medicinal chemistry points of view after the discovery of the naturally occurring C-nucleoside antibiotic pyrazofurin (7). 

The Naturally Occurring Pyrazole C-Nucleoside Antibiotic Pyrazofurin and Its Congeners 

Studies on the biosynthesis of pyrazofurin using labeled nutrients in the fermentation media of Streptomyces candidus indicated that o-ribose and L-glutamate are its principal biosynthetic precursors [80JCS(CC)917]. 

Pyrazofurin (7) and its a-anomer pyrazofurin B (8) were obtained upon diazotization of the 3-oxo-2-(a-D-ribofuranosyl)glutarate derivative 252 followed by cyclization and ammonolysis prolonging the time of ammonolysis 

In search of more biologically active but less toxic congeners of pyrazofurin, compounds 267-271 (76USP3960836 77USP4053689 86JMC268), as well as 0-,N-,0,N-acetyl, propyl, palmitoyl, and adamantoyl derivatives 

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