A novel synthesis of C-nucleosides having pyrrolo[1,2-f]pteridine, 6- and 8-deazapyrrolo[1,2-f]-pteridine ring systems from 6-hydroxy-6-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-2H-pyran-3(6H)-one

A versatile intermediate pyranulose glycoside (1) for C-nucleoside synthesi s was treated with 4,5-diaminopyrimidine in AcOH to give 1-(2,3,5-tri-O-ben zoyl-beta-D-ribofuranosyl)pyrrolo[1,2-f]pteridine (2) in 58% yield. However , treatment of 1 with 4,5,6-triaminopyrimidine in TFA afforded the 4-aminop teridine (4) without formation of the pyrrolo[1,2-f]pteridine. Similar reac tion of 2,3- and 3,4-diaminopyridines with 1 in AcOH led to formation of 8- and 6-deazapyrrolo[1,2-f]pteridines (5 and 6), respectively. Removal of th e sugar protecting groups in 2, 5, and 6 with sodium carbonate gave the dep rotected C-nucleosides (7, 8 and 9).