Enantiodivergent syntheses of cycloheptenone intermediates for guaiane sesquiterpenes

The syntheses of enantiomeric 6-isopropenyl-3-methyl-2-cycloheptenones 16 and 22 have been effected starting from ( R)-(−)-carvone. In the synthesis of 16, ( R)-(−)-carvone was reduced and the resulting dihydrocarvone transformed regioselectively into silyl enol ethers. Cyclopropanation with dibromo...

Full description

Saved in:
Bibliographic Details
Published in:Tetrahedron: asymmetry 2000-10, Vol.11 (20), p.4093-4103
Main Authors: Leiva de Faria, Mary, de A. Magalhães, Ruy, Silva, Fernando C, de O. Matias, Luiz G, Ceschi, Marco A, Brocksom, Ursula, John Brocksom, Timothy
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The syntheses of enantiomeric 6-isopropenyl-3-methyl-2-cycloheptenones 16 and 22 have been effected starting from ( R)-(−)-carvone. In the synthesis of 16, ( R)-(−)-carvone was reduced and the resulting dihydrocarvone transformed regioselectively into silyl enol ethers. Cyclopropanation with dibromocarbene and in situ rearrangement gave an α-bromo-cycloheptenone which was reduced to the ( R)-(+)-cycloheptenone 16. In the synthesis of 22, ( R)-(−)-carvone was cyclopropanated with a sulfur ylide, followed by reduction with LiAlH 4 and acid-catalyzed cyclopropylcarbinyl rearrangement to afford a cycloheptenol. Oxidation and double bond conjugation led to the ( S)-(−)-cycloheptenone 22 in a partially racemized form. Four cycloheptenones have been obtained and are suitable intermediates for the enantiodivergent syntheses of guaiane sesquiterpenes.
ISSN:0957-4166
1362-511X
DOI:10.1016/S0957-4166(00)00387-6