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Asymmetric control in the Pictet-Spengler reaction by means of N-protected amino acids as chiral auxiliary groups

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons98735

Waldmann,  Herbert
Abt. IV: Chemische Biologie, Max Planck Institute of Molecular Physiology, Max Planck Society;

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Schmidt, G., Waldmann, H., Henke, H., & Burkard, M. (1996). Asymmetric control in the Pictet-Spengler reaction by means of N-protected amino acids as chiral auxiliary groups. CHEMISTRY-A EUROPEAN JOURNAL, 2(12), 1566-1571. doi:10.1002/chem.19960021215.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0014-71F1-D
Abstract
Aromatic and aliphatic Schiff bases of tryptamine react with Fmoc- or ph-thaloyl-protected amino acid chlorides to form N-acyliminium intermediates, which, in the presence of titanium alkoxides at room temperature, undergo Pictet-Spengler reactions to give tetrahydro-beta-carbolines with diastereomeric ratios of up to 99:1. The chiral auxiliary can be removed from the Pictet-Spengler adducts by means of a simple reduction. To rationalize the observed stereoselectivity a transition-state model is proposed in which the titanium atom coordinates both the carbonyl group of the N-acyliminium ion and the amino acid protecting group.