Total Synthesis of Limonin

Limonoids are highly oxygenated C13α‐triterpenes and common secondary metabolites. Several hundred congeners have been isolated to date. The first total synthesis of (±)‐limonin, the flagship congener of the limonoids, is now reported and features 1) a tandem radical cyclization generating the BCD r...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2015-07, Vol.54 (29), p.8538-8541
Main Authors: Yamashita, Shuji, Naruko, Akito, Nakazawa, Yuki, Zhao, Le, Hayashi, Yujiro, Hirama, Masahiro
Format: Article
Language:English
Subjects:
Congeners
Construction
Cycloaddition
Limonoids
Oxidation
Oxygenated
radical reactions
Radicals
Synthesis
total synthesis
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Summary:Limonoids are highly oxygenated C13α‐triterpenes and common secondary metabolites. Several hundred congeners have been isolated to date. The first total synthesis of (±)‐limonin, the flagship congener of the limonoids, is now reported and features 1) a tandem radical cyclization generating the BCD ring system with the C13α configuration that is essential to the limonoids and a Robinson annulation to construct the limonoid androstane framework, 2) a singlet‐oxygen cycloaddition and a Baeyer–Villiger oxidation to synthesize the highly oxidized D ring, and 3) a Suárez reaction to construct the unique AA′ ring system. Limonin, not limonene: The flagship congener of the limonoid natural‐product family, limonin, was synthesized for the first time. Geraniol was employed as the starting material, and key reactions for the efficient construction of the limonin framework included a tandem radical cyclization, a singlet‐oxygen cycloaddition, Baeyer–Villiger oxidation, and a Suárez reaction.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201503794