title: Divergent total syntheses of (-)-aspidospermine and (+)-spegazzinine.
abstract: Divergent total syntheses of (+)-spegazzinine (1) and (-)-aspidospermine (2) and their extensions to the synthesis of C19-epi-aspidospermine and C3-epi-spegazzinine are detailed, confirming the relative stereochemistry and establishing the absolute configuration of (+)-spegazzinine. A powerful intramolecular [4 + 2]/[3 + 2] cycloaddition cascade of a 1,3,4-oxadiazole provided the pentacyclic skeleton and all the requisite stereochemistry of the natural products in a single reaction that forms three rings, four C-C bonds, and five stereocenters.
authors.affiliation: Department of Chemistry and Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Lajiness
authors.forename: Wanlong
authors.initials: W
authors.lastname: Jiang
authors.forename: Dale L
authors.initials: DL
authors.lastname: Boger
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010069:Oxadiazoles / Q000737:chemistry; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D026121:Indole Alkaloids; D010069:Oxadiazoles; D011804:Quinolines; C016757:spegazzinine; C091896:aspidospermine