Synthesis of 2-pyranosyl benzothiazoles, benzimidazoles and benzoxazoles via nucleophilic addition reactions of pyranosyl nitrile oxides

Reaction of per-O-acetylated-β-d-pyranosyl nitrile oxides, generated by dehydrochlorination of the corresponding hydroximoyl chlorides, with 2-aminothiophenol afforded 2-(β-d-pyranosyl)benzothiazoles. 1,2-Diaminobenzene and 2-aminophenol reacted similarly to yield 2-(β-d-pyranosyl)benzimidazoles and 2-(β-d-pyranosyl)benzoxazoles, respectively. The structures of 2-β-d-glucopyranosylbenzimidazole (17), 2-(2,3,4-tri-O-acetyl-β-d-xylopyranosyl)benzimidazole (19) and the xylopyranosyl thiohydroximate 13 were established by X-ray crystallography.