Synthesis of Quinazoline C-Nucleosides: A New Class of 6:6 Bicyclic Purine-Like Analogues.1

The quinazoline C-nucleoside congeners of adenosine (1) and inosine (2) have been obtained by radical-induced addition of 4-bromobutyronitrile to C-ribosyl acrylonitrile 10. A base-catalyzed Ziegler-Thorpe cyclization of the dinitrile thus obtained (11) followed by aromatization with DDQ afforded key intermediate 6-ribosylated anthranilonitrile 14 and its α-isomer. Annulation of a pyrimidine ring onto 14 or onto the corresponding o-amino-amide followed by deblocking with MeOH/HCl finally gave 1 or 2 respectively.