title: Eight-Step Enantioselective Total Synthesis of (-)-Cycloclavine.
abstract: The first enantioselective total synthesis of (-)-cycloclavine was accomplished in 8 steps and 7.1 % overall yield. Key features include the first catalytic asymmetric cyclopropanation of allene, mediated by the dirhodium catalyst Rh2(S-TBPTTL)4, and the enone 1,2-addition of a new TEMPO carbamate methyl carbanion. An intramolecular strain-promoted Diels-Alder methylenecyclopropane (IMDAMC) reaction provided a pivotal tricyclic enone intermediate with more than 99 % ee after crystallization. The synthesis of (-)-1 was completed by a late-stage intramolecular Diels-Alder furan (IMDAF) cycloaddition to install the indole.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: McCabe
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
authors.forename: Peter
authors.identifier: 0000-0001-7693-5863
authors.initials: P
authors.lastname: Wipf
mesh_terms: D018360:Crystallography, X-Ray; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D026121:Indole Alkaloids; C560517:cycloclavine
keywords: allene; clavine alkaloids; cycloaddition; cyclopropanation; enantioselectivity