Total, asymmetric synthesis of ethyl D-ido-4-heptulosuronate derivatives starting from diethyl 4-oxopimelate
Bromination of diethyl 4-oxopimelate, followed by double elimination of HBr and ketalization provided diethyl (E,E)-4,4-(ethylidenedioxy)hepta-2,5-dienedioate 4. Sharpless asymmetric dihydroxylation of 4 produced diethyl (2S,3S)-4,4-(ethylidenedioxy)-2,3-dihydroxyhept-5-eneiodate (+)-5, with 78% e.e. The corresponding tetrol could not be obtained in one step. Silylation of (+)-5 and a second asymmetric dihydroxylation, followed by silylation led to 20% of meso-diester 9 and 60% of diethyl (2S,3S,5S,6S)-2,3,5,6-tetrakis[(t-butyl) 4,4-(ethylidenedioxy)heptanedioate (-)-10. Reductive desymmetrization of (-)-10 with DIBAL-H furnished, after selective oxidation, ethyl (2S,3S,5S,6S)-2,3,5,6-tetrakis-[(t-butyl oxoheptanoate (+)-13 which was then converted into ethyl 1,2,3,6-0-tetraacetyl-4,4-ethylidenedioxy-alpha- and beta-D-ido-heptapyranuronate (-)-15 alpha,beta and into the corresponding 3-(alpha-D-pyranosyl)propene (-)-16. (C) 1999 Elsevier Science Ltd. All rights reserved.
Keywords: stereoselective synthesis ; chemoenzymatic synthesis ; neisseria-meningitidis ; escherichia-coli ; destomic acid ; hydroxy group ; c-glycosides ; core region ; lipopolysaccharide ; dihydroxylation
Record created on 2005-11-09, modified on 2016-08-08