Enantioselective Synthesis and Absolute Stereochemistry of Both the Enantiomers of trans-Magnolione, a Fragrance Structurally Related to trans-Methyl Jasmonate.

Abstract Both enantiomers of the trans stereoisomer of magnolione 4 have been prepared by asymmetric Michael addition of ethyl acetoacetate to 2-pentylcyclopentenone, followed by hydrolysis/decarboxylation. The Michael reaction occurs under solid/liquid phase transfer catalysis in the presence of N -methylanthracenylquininium (or quinidinium) chloride. Enantiomeric excesses up to 76% are obtained. The trans structure of the compounds has been fully established by a careful NMR analysis, while the absolute configuration has been assigned as (2 S ,3 S ) for (+)- 4 by the analysis of the CD spectrum.