SYNTHESIS OF INDAZOLE C-NUCLEOSIDES AND ANALOGS

1‐Deoxy‐1‐diazo‐3,6‐anhydro‐4,5,7‐tri‐O‐benzoyl‐D‐allo‐heptulosc (III) has been prepared from 2,5‐anhydro‐3,4,6‐tri‐O‐benzoyl‐D‐allonic acid. 1,3‐Dipolar cycloaddition of III to benzyne afforded the indazole C‐nucleoside analog V. Cycloaddition of methyl 6‐deoxy‐6‐diazo‐2,3‐O‐isopropylidene‐β‐D‐ribohexofuranosid‐5‐ulose (IV) to the benzyne generated from 5‐methyl‐anthranilic acid gave a mixture of the β‐isomeric C‐glycosylindazoles VI and VII along with traces of the corresponding α‐anomers VIa and VIIa. Finally, a multistep transformation of the acyclic carbohydrate moiety of 2,3,4,5‐tetra‐O‐acetyl‐1‐(indazol‐3‐yl)‐keto‐D‐ribopentulose (I, R = H, n = 3, D‐ribo) led to the C‐nucleoside indazole, 3‐(2,3‐O‐isopropylidene‐β‐D‐ribofuranosyl)‐indazol (X), as the major product. Copyright © 1979 Journal of Heterocyclic Chemistry