Nitrile oxide/isoxazoline approach to higher monosaccharides: synthesis of 7-deoxy-nonose and -decose derivatives 1

Abstract

7-Deoxy-D-ribo-D-galacto - and 7-deoxy-D-xylo-D-galacto-decopy ranoside derivatives 11 and 12 have been prepared by a sequence involving diastereoselective cycloaddition of 2,3-O-isopropylidene-D-glyceronitrile oxide to D-galactose-derived alkene 3 to afford the isoxazoline 5 as the major adduct, followed by reductive hydrolytic cleavage of the isoxazoline and reduction of the resulting β-hydroxy ketone. The configuration of the new chiral centre (C-8) in compounds 11 and 12 is established by NMR analysis of their 6,8-O-isopropylidene derivatives 13 and 14. 7-Deoxy-L-threo-D-galacto- and 7-deoxy-D-erythro-D-galacto-non opyranosides 15 and 16 are prepared similarly from alkene 3 and ethoxycarbonylformonitrile oxide via isoxazolines 8 and 17, and β-hydroxy ketone 18. The 6,7-dideoxynon-6-enos-8-ulose 19 is also prepared from isoxazoline 5.