title: Approach to the homoerythrina alkaloids using a tandem N-alkylation/azomethine ylide cycloaddition.
abstract: Synthetic efforts toward the homoerythrina alkaloids 1-3 are described. Two separate model systems guided the pivotal [3 + 2] azomethine ylide cycloaddition cascade to form the A-C rings of these alkaloids. The cycloaddition precursors 63 and 68, prepared in nine and ten steps, respectively, from alkyne 47, each contain an enolizable ketone, a tethered electrophile, and an electron-poor dipolarophile. Heating 63 and 68 with the stannyl amine 17 generated demethoxyschelhammeridine 65 and demethoxyschelhammericine 70, the products of intramolecular azomethine ylide cycloadditions. Subsequent attempts to install the C-3 methoxy group of 1-3 are also described.
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA. wpearson@berryassoc.com
authors.forename: William H
authors.initials: WH
authors.lastname: Pearson
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Kropf
authors.forename: Allison L
authors.initials: AL
authors.lastname: Choy
authors.forename: Ill Young
authors.initials: IY
authors.lastname: Lee
authors.forename: Jeff W
authors.initials: JW
authors.lastname: Kampf
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis / Q000737:chemistry*; D000478:Alkylation; D000588:Amines / Q000737:chemistry; D001391:Azo Compounds / Q000737:chemistry*; D003500:Cyclization; D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D000588:Amines; D001391:Azo Compounds; D006576:Heterocyclic Compounds, 4 or More Rings; D007659:Ketones; D013882:Thiosemicarbazones; C512188:azomethine