title: Asymmetric Formal Synthesis of Azadirachtin.
abstract: An asymmetric formal synthesis of azadirachtin, a potent insect antifeedant, was accomplished in 30 steps to Ley's synthetic intermediate (longest linear sequence). The synthesis features: 1) rapid access to the optically active right-hand segment starting from the known 5-hydroxymethyl-2-cyclopentenone scaffold; 2) construction of the B and E rings by a key intramolecular tandem radical cyclization; 3) formation of the hemiacetal moiety in the C ring through the α-oxidation of the six-membered lactone followed by methanolysis.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 (Japan).
authors.forename: Naoki
authors.initials: N
authors.lastname: Mori
authors.affiliation: Current address: Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-0193 (Japan).
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kitahara
authors.affiliation: Present address: Photosensitive Materials Research Center, Toyo Gosei Co., Ltd, 4-2-1 Wakahagi, Inzai-shi, Chiba 270-1609 (Japan).
authors.forename: Kenji
authors.initials: K
authors.lastname: Mori
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657 (Japan). ashuten@mail.ecc.u-tokyo.ac.jp.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D036701:Limonins / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation
chemical_list: D036701:Limonins; C010329:azadirachtin
keywords: acetals; cyclizations; natural products; radicals; stereoselectivity