Résumé
Giese's radical glycosidation of (-)-(1S,4R,5R,6R)-5-exo-(benzeneselenyl)-6-endo-chloro-3-methylidene-7-o xabicyclo[2.2.1]-heptan-2-one with tetra-O-acetylbromo-alpha-D-galactopyranose gave a C-galactoside that was converted into (+)-(1S,2R,3S,4R)-6-chloro-3,3-endo-[(2',3',4',6'-tetra-O-acetyl-alpha-D -galactopyranosyl)methyl]-7-oxa-bicyclo[2.2.1]hept-5-en-2-endo-yl acetate ((+)-6). Treatment of (+)-6 with HBr, then with LiN3 and subsequent reduction afforded (3S,4R,5R,6S)-3-amino-1-chloro-4-[(alpha-D-galactopyranosyl)methyl]-cycl ohex-1-en-5,6-diol ((+)-10). Acidic hydrolysis of (+)-6 provided the (3R,4R,5R,6S)-1-chloro-4-[(alpha-D-galactopyranosyl)methyl]-cyclohex-hex -1-en-3,5,6-triol derivative (+)-11 or the (4R,5R,6S)-4-[(alpha-D-galactopyranosyl)methyl]-5,6-dihydroxycyclohex-2- en-1-one derivative (-)-12 selectively.