Abstract
3‐O‐Benzyl‐6‐deoxy‐1,2‐O‐isopropylidene‐α‐d‐xylo‐hept‐5‐ulofuranurononitrile (1) was reacted with N,N‐dimethylformamide dimethylacetal in tetrahydrofuran to furnish the (E)‐3‐O‐benzyl‐6‐deoxy‐6‐dimethylaminomethylene‐1,2‐O‐isopropylidene‐α‐d‐xylo‐hept‐5‐ulofuranurononitrile (2) as a major product. Furthermore, treatment of compound 1 with carbon disulphide and methyl iodide under basic conditions afforded 3‐O‐benzyl‐6‐deoxy‐1,2‐O‐isopropylidene‐6‐[bis(methylsulfanyl)methylene]‐α‐d‐xylo‐hept‐5‐ulofuranurononitrile (6). Reaction of 2 and 6 with hydrazines yielded the “reversed” pyrazole‐C‐nucleoside analogs 4, 5a, 5b, 7, 8, and 9, respectively.