title: Total synthesis of neodolastane diterpenes trichoaurantianolides C and D.
abstract: The first total synthesis of trichoaurantianolides C and D is described. An enantiocontrolled pathway leads to rapid construction of the tricyclic carbon skeleton and establishes the trans-dimethyl geometry of the quaternary bridgehead carbons via a reductive cyclization. Application of the π-allyl Stille cross-coupling leads to a nonracemic allylic alcohol as a prerequisite for the introduction of asymmetry in the cycloheptane system. Two strategies have been examined for elaboration of the unsaturated tetrahydrofuranyl ring from a common tricyclic intermediate. These efforts reveal a number of unanticipated issues of reactivity and significant stereochemical requirements for a novel acyloin rearrangement as well as the elimination and cyclodehydration of chiral α-hydroxy ketones. Key reactions leading to completion of the synthesis include the stereoselective addition of isopropenyllithium TMEDA complex and a facile chemoselective oxidation with selenium dioxide.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: David R
authors.initials: DR
authors.lastname: Williams
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Gladen
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Pinchman
mesh_terms: D002384:Catalysis; D003500:Cyclization; D004224:Diterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D007659:Ketones / Q000737:chemistry; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D004224:Diterpenes; D007659:Ketones; C000605251:trichoaurantianolide C; C000605252:trichoaurantianolide D