E. Butkus, A. Žilinskas, S. Stončius
Apr 19, 2002
Citations
0
Influential Citations
17
Citations
Journal
Tetrahedron-asymmetry
Abstract
Abstract The synthesis of chiral tricyclo[4.3.0.0 3,8 ]nonane-4,5-dione was accomplished starting from enantiomerically pure (+)-(1 S ,5 S )-bicyclo[3.3.1]nonane-2,6-dione 1 . Ring contraction of the latter with thallium(III) nitrate proceeded with high stereoselectivity giving exclusively methyl (+)-(1 S ,4 S )-(+)- exo , exo -bicyclo[2.2.1]heptan-2,5-dicarboxylate 2 . Inversion of the configuration of this diester to the required di- endo derivative was realized via the following reaction sequence. Bromination of the corresponding acid dichloroanhydride and subsequent reduction with zinc in acetic acid gave a diastereoisomeric mixture of esters, from which the endo , endo -ester 5 was isolated by column chromatography. Acyloin condensation of the latter with trimethylchlorosilane in toluene led to intramolecular ring closure, and subsequent oxidation of the enol silyl ether 7 in situ gave tricyclo[4.3.0.0 3,8 ]nonane-4,5-dione 8 . The chiroptical properties of this cage molecule were studied by electronic and vibrational circular dichroism spectroscopy. The (1 R ,3 R ,6 R ,8 R ) absolute configuration of the title structure was also unambiguously proved.