title: Asymmetric synthesis of (-)-eburnamonine and (+)-epi-eburnamonine from (4S)-4-ethyl-4-[2-(hydroxycarbonyl)ethyl]-2-butyrolactone.
abstract: The key chiral nonracemic 4,4-disubstituted 2-butyrolactone carboxylic acid, (S)-4, is readily accessible via an efficient and stereospecific dirhodium(II) tetraacetate catalyzed tertiary C-H insertion reaction of the diazomalonate (S)-5. The coupling of the acid (S)-4 with tryptamine produces the amide (S)-3, which is then transformed into the aldehyde 23 and hydroxy-lactam 24. Acid-mediated Pictet-Spengler cyclization of 23 and 24 produces the tetracyclic indole lactams (1S,12bS)-25a and (1S,12bR)-25b. Compounds 25a and 25b are converted, via the lactam alcohols 30a and 30b, to (-)-eburnamonine (1a) and (+)-epi-eburnamonine (1b).
authors.affiliation: Department of Chemistry and Biochemistry, University of Regina, Regina, Saskatchewan, S4S 0A2, Canada. Andrew.Wee@uregina.ca
authors.forename: A G
authors.initials: AG
authors.lastname: Wee
authors.forename: Q
authors.initials: Q
authors.lastname: Yu
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism; D014748:Vinca Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C445790:4-4-ethyl-4-(2-(hydroxycarbonyl)ethyl)-2-butyrolactone; D007202:Indicators and Reagents; D014748:Vinca Alkaloids; C016422:eburnamonine; D015107:4-Butyrolactone