- Enantioselective synthesis of tryptophan derivatives by a tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction.
Enantioselective synthesis of tryptophan derivatives by a tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction.
Journal of the American Chemical Society (2012-03-07)
Madeleine E Kieffer, Lindsay M Repka, Sarah E Reisman
PMID22390403
摘要
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.
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