title: Concise total syntheses of the bioactive mesotricyclic diterpenoids jatrophatrione and citlalitrione.
abstract: The highly functionalized [5.9.5] tricyclic framework resident in jatrophatrione (1) and citlalitrione (2) has been synthesized. The route begins with the tandem anionic oxy-Cope rearrangement/methylation/transannular ene cyclization of 21 and subsequent introduction of a conjugated enone double bond. Hydroxyl-directed 1,4-reduction of this functionality in 25 with LiAlH(4)/CuI/hexamethylphosphoramide/tetrahydrofuran sets the stage for the implementation of a Grob fragmentation and expedited generation of 27. Stereocontrolled intramolecular hydrosilylation allows for the subsequent introduction of a cyclic carbonate as in 53. This intermediate undergoes remarkably efficient, fully regiocontrolled Treibs reaction to generate 54, with this maneuver serving as a pivotal step for making 1 available five steps later. Treatment of 1 with m-chloroperbenzoic acid leads to 2, with attack occurring preferentially on a alpha-face of the double bond more remote to the carbonyl.
authors.affiliation: Evans Chemical Laboratories, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Jiong
authors.initials: J
authors.lastname: Yang
authors.forename: Yun Oliver
authors.initials: YO
authors.lastname: Long
authors.forename: Leo A
authors.initials: LA
authors.lastname: Paquette
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000138:chemical synthesis*; D004224:Diterpenes / Q000138:chemical synthesis*; D031286:Jatropha / Q000737:chemistry
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004224:Diterpenes; C058327:citlalitrione; C012392:jatrophatrione