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Angew Chem Int Ed Engl
; 54(29): 8538-41, 2015 Jul 13.
Article
in English
| MEDLINE
| ID: mdl-26036432
ABSTRACT
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)â 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)â a singlet-oxygen cycloaddition and a Baeyer-Villiger oxidation to synthesize the highly oxidized Dâ ring, and 3)â a Suárez reaction to construct the unique AA' ring system.