title: Enantioselective synthesis of tryptophan derivatives by a tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction.
abstract: The tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction between 2-substituted indoles and methyl 2-acetamidoacrylate is reported. The reaction is catalyzed by (R)-3,3'-dibromo-BINOL in the presence of stoichiometric SnCl(4), and is the first example of a tandem conjugate addition/asymmetric protonation reaction using a BINOL·SnCl(4) complex as the catalyst. A range of indoles furnished synthetic tryptophan derivatives in good yields and high levels of enantioselectivity, even on a preparative scale. The convergent nature of this transformation should lend itself to the preparation of unnatural tryptophan derivatives for use in a broad array of synthetic and biological applications.
authors.affiliation: The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
authors.forename: Madeleine E
authors.initials: ME
authors.lastname: Kieffer
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Repka
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Reisman
mesh_terms: D000179:Acrylates / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D015394:Molecular Structure; D011522:Protons; D013237:Stereoisomerism; D014364:Tryptophan / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000179:Acrylates; D007211:Indoles; D011522:Protons; C011392:N-acetyldehydroalanine methyl ester; D014364:Tryptophan