Generation and cycloaddition reactions of pyranose-1-carbonitrile oxides

Stannate(II) reduction of the beta -D-glucopyranosylnitromethane derivative 4 affords aldoxime 5, which provides access to the nitrile oxide 7, either on treatment with aq. hypochlorite, or via conversion to the hydroximoyl c hloride 11 followed by base-mediated dehydrohalogenation. D-Galactose-, D-m annose- and D-xylose-derived nitrile oxides are generated similarly. The ni trile oxides either dimerise to 3,4-dipyranosyl-1,2,5-oxadiazole N-oxides o r are trapped as cycloadducts in the presence of dipolarophiles. (C) 2001 E lsevier Science Ltd. All rights reserved.