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Enantioselective Syntheses and Fragrance Properties of the Four Stereoisomers of Magnolione® (Magnolia Ketone)

✍ Scribed by Andrea Quendolin Stang; Günter Helmchen

Publisher
John Wiley and Sons
Year
2005
Tongue
German
Weight
124 KB
Volume
88
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Enantioselective total syntheses of the four stereoisomers of the fragrance Magnolione® (1) are described. Key step is a Pd‐catalyzed asymmetric allylic alkylation displaying enantiomer excess of ≥ 99% (Scheme 2). The resultant methyl α‐acetyl‐2‐pentylcyclopent‐2‐ene‐1‐acetate) was subjected to demethoxycarbonylation, carbonyl protection by acetalization, and epoxidation (Schemes 2 and 3). Subsequent Lewis acid catalyzed epoxide/ ketone rearrangement followed by deprotection gave cis/trans mixtures of Magnolione® in 28% overall yield (Scheme 3). The cis/trans isomers were separated by prep. HPLC, and fragrance properties as well as odor threshold values were determined (Table 2).

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