Synthesis of l-ribofuranosyl C-nucleosides

C-Nucleosides, 4-amino-8-(β-l-ribofuranosyl)pyrazolo[1,5-a]-1,3,5-triazine (12) and 4-amino-7-(β-l-ribofuranosyl)-5H-pyrrolo[3,2-d]pyrimidine (l-9-deazaadenosine, 22), were synthesized from the key intermediate, 3-dimethylamino-2-(2,3-O-isopropylidene-5-O-trityl-l-ribofuranosyl)acrylonitrile (8), which was prepared from l-xylose in 11 steps.