Chemoselective synthesis of 3,6,7-trisubstituted 2-(2,3:5,6-di-O-isopropylidene-β-D-mannofuranosyloxy]- and 2-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glucopyranosyloxy)quinoxaline derivatives

Abstract

A series of quinoxaline O-nucleosides, 3,6,7-trisubstituted 2-(2,3:5,6-di-O-isopropylidene-β-D-mannofuranosyl-1-yl)quinoxalines and 2-(2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-β-D-glucopyranosyl)quinoxalines, was prepared by the reaction of 3,6,7-trisubstituted quinoxalin-2(1H)-ones with the corresponding protected α-chlorosugars in the presence of NaH. The reaction proceeded chemoselectively to give products of O-substitution with β-configuration at anomeric carbon, as proved by NMR data. The deprotection of the 1-(2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-β-D-glucopyranosyl)quinoxalines was achieved by stirring in ammonia–methanol mixture to afford free O-quinoxaline nucleoside analogs.