A New Conversion Method from (–)-Limonene to Nepetalactones

Abstract

This paper describes the conversions of (–)-limonene to four nepetalactones (1, 2, ent-3 and 4) in a stereocontrolled manner. The cw-3,4-disubstituted cyclopentanone (5) obtained from (–)-limonene via Rh(I)-catalyzed cyclization of the 4-pentenal, could be converted to the bicyclo-[3.3.0]octenone (6). After the stereoselective conversion of 6 into the diastereomeric isomers of the ketones (8 and 16), a sequence of reactions involving the silyl enol ethers (18 and 19), ozonolysis, and subsequent lactonization afforded the target molecules. © 1988, The Pharmaceutical Society of Japan. All rights reserved.