title: Total synthesis of (-)-kopsinine andent-(+)-kopsinine.
abstract: The total synthesis of (-)-kopsinine and its unnatural enantiomer is detailed, enlisting a late-stage SmI2-mediated transannular free radical conjugate addition reaction for construction of the core bicyclo[2.2.2]octane ring system with strategic C21-C2 bond formation. Key to the approach is assemblage of the underlying skeleton by an intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole that provided the precursor C21 functionalized pentacyclic ring system1in a single step in which the C3 methyl ester found in the natural product served as a key 1,3,4-oxadiazole substituent, activating it for participation in the initiating Diels-Alder reaction and stabilizing the intermediate 1,3-dipole.
authors.affiliation: Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037.
authors.forename: Kiyoun
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037.
authors.forename: Dale L
authors.initials: DL
authors.lastname: Boger