title: Brønsted acid mediated cyclization of enaminones. Rapid and efficient access to the tetracyclic framework of the Strychnos alkaloids.
abstract: The development of an efficient diastereoselective method that permits rapid construction of the tetracyclic core 17 of the Strychnos-Aspidosperma alkaloids is described. Enaminone 16, synthesized in high yield, has been cyclized under the influence of a Brønsted acid to provide the core tetracyclic framework 17 of the Strychnos alkaloids in optically active form or alternatively to the β-ketoester tetrahydro-β-carboline (THBC) unit 18, by varying the equivalents of acid and the molar concentration. Attempts to utilize 18 to form the C₇-C₁₆ bond of the akuammiline related alkaloids represented by strictamine (22), using metal-carbenoid chemistry, are also described.
authors.affiliation: Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA.
authors.forename: Rahul V
authors.initials: RV
authors.lastname: Edwankar
authors.forename: Chitra R
authors.initials: CR
authors.lastname: Edwankar
authors.forename: Ojas A
authors.initials: OA
authors.lastname: Namjoshi
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Deschamps
authors.forename: James M
authors.initials: JM
authors.lastname: Cook
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis / Q000737:chemistry; D003500:Cyclization; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D031451:Strychnos / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D026121:Indole Alkaloids; C022062:strictamine