title: Syntheses of strychnine, norfluorocurarine, dehydrodesacetylretuline, and valparicine enabled by intramolecular cycloadditions of Zincke aldehydes.
abstract: A full account of the development of the base-mediated intramolecular Diels-Alder cycloadditions of tryptamine-derived Zincke aldehydes is described. This important complexity-generating transformation provides the tetracyclic core of many indole monoterpene alkaloids in only three steps from commercially available starting materials and played a key role in short syntheses of norfluorocurarine (five steps), dehydrodesacetylretuline (six steps), valparicine (seven steps), and strychnine (six steps). Reasonable mechanistic possibilities for this reaction, a surprisingly facile dimerization of the products, and an unexpected cycloreversion to regenerate Zincke aldehydes under specific conditions are also discussed.
authors.affiliation: Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
authors.forename: David B C
authors.initials: DB
authors.lastname: Martin
authors.forename: Lucas Q
authors.initials: LQ
authors.lastname: Nguyen
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Vanderwal
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D003500:Cyclization; D019281:Dimerization; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013331:Strychnine / Q000138:chemical synthesis* / Q000737:chemistry; D014403:Tubocurarine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D000447:Aldehydes; D026121:Indole Alkaloids; C541002:norfluorocurarine; C523218:valparicine; D013331:Strychnine; D014403:Tubocurarine