Synthesis of imidazo[4,5-b]pyrazine nucleosides

Abstract

5,6-Dimethyl-1-(β-D-ribofuranosyl)imidazo[4,5-b]pyrazine (12) has been synthesised by three different routes: (a) glycosylation of thetrimethylsilyl derivative (5) of 5,6-dimethylimidazo[4,5-b]pyrazine, (b) the fusion procedure, and (c) ring closure of an imidazole nucleoside. The assignment of the site of ribosylation and of the anomeric configuration of compound (12) and the imidazo[4,5-b]pyrazine nucleosides -(10) and (11) is discussed.