Abstract
A novel chiral source, 5-( R)-[(1 R,2 S,5 R)-(−)-menthyloxy]-3-bromo-2(5H)-furanone ( 5a), was obtained in 46% yield with d.e.≥98% from the epimeric mixture of 5-( l-menthyloxy)-3-bromo-2(5H)-furanone ( 5a+ 5b) obtained via the bromination of an epimeric mixture of 5-( l-menthyloxy)-2(5H)-furanone ( 3a+ 3b) followed by the elimination of hydrogen bromide. The asymmetric reaction of 5a with a nucleophilic alcohol afforded enantiomerically pure spiro-cyclopropane derivatives containing four stereogenic centers, 9a– 9e, in 50–68% yield with d.e.≥98%. The enantiomerically pure compounds 9a– 9e were identified on the basis of their analytical data and spectroscopic data, such as [α] D 20, UV, IR, 1H NMR, 13C NMR, MS and elementary analysis. The absolute configuration of the chiral spiro-cyclopropane compound 9a was established by X-ray crystallography.
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