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Asymmetric Pictet–Spengler Reactions Employing N,N-Phthaloyl Amino Acids as Chiral Auxiliary Groups

Authors

  • Prof. Dr. Herbert Waldmann,

    Corresponding author
    1. Institut für Organische Chemie der Universität, Richard-Willstätter-Allee 2, D-76128 Karlsruhe (Germany), Telefax: Int. code + (721) 608-4825
    • Institut für Organische Chemie der Universität, Richard-Willstätter-Allee 2, D-76128 Karlsruhe (Germany), Telefax: Int. code + (721) 608-4825
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  • Dipl.-Chem. Gunther Schmidt,

    1. Institut für Organische Chemie der Universität, Richard-Willstätter-Allee 2, D-76128 Karlsruhe (Germany), Telefax: Int. code + (721) 608-4825
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  • Dr. Henning Henke,

    1. Institut für Anorganische Chemie der Universität Karlsruhe
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  • Dr. Michael Burkard

    1. Institut für Anorganische Chemie der Universität Karlsruhe
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  • This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Degussa AG for the donation of amino acids.

  • Dedicated to Professor Ivar Ugi on the occasion of his 65th birthday

Abstract

original image

Both aromatic and aliphatic Schiff bases 1 can be cyclized asymmetrically in the presence of titanium alkoxides if N,N-phthaloyl-protected amino acids are employed as chiral auxiliaries. The desired heterocycles 3, which are suitable for alkaloid syntheses, are formed with diastereomer ratios of up to 99%. R [DOUBLE BOND] nPr, iPr; R1 [DOUBLE BOND] Me, Et, iPr, Ph, Ar; R2 [DOUBLE BOND] Me, iPr, tBu.

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