title: Total Synthesis of Limonin.
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) 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.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan). syamashita@fas.harvard.edu.
authors.forename: Shuji
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).
authors.forename: Akito
authors.initials: A
authors.lastname: Naruko
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakazawa
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).
authors.forename: Le
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Hayashi
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).|Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aramaki-aza aoba, Aoba-ku, Sendai 980-8578 (Japan).
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hirama
keywords: cycloaddition; limonoids; oxidation; radical reactions; total synthesis