title: Enantioselective total synthesis of guanacastepene N using an uncommon 7-endo Heck cyclization as a pivotal step.
abstract: A convergent, enantioselective total synthesis of (+)-guanacastepene N was developed that features a 7-endo Heck cyclization as the key step. In the course of this synthesis, short syntheses of the enantiomerically pure cyclopentenone and cyclohexene building blocks 5 and 6, which constitute A and C ring fragments of guanacastepene N, were developed. These fragments were linked by a challenging conjugate addition reaction that also generated the C11 quaternary carbon stereocenter. Regioselective 7-endo Heck cyclization gave rise to a tricyclic intermediate, which was elaborated to complete the first total synthesis of guanacastepene N and the second enantioselective total synthesis of a guanacastepene natural product.
authors.affiliation: Department of Chemistry, 1102 Natural Sciences II, University of California, Irvine, 92697-2025, USA.
authors.forename: Shin
authors.initials: S
authors.lastname: Iimura
authors.forename: Larry E
authors.initials: LE
authors.lastname: Overman
authors.forename: Ralph
authors.initials: R
authors.lastname: Paulini
authors.forename: Armen
authors.initials: A
authors.lastname: Zakarian
mesh_terms: D003500:Cyclization; D004224:Diterpenes / Q000138:chemical synthesis / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D004224:Diterpenes; C409194:guanacastepene