Mitsuhashi K, Ito R, Arai T, Yanagisawa A. Catalytic Asymmetric Protonation of Lithium Enolates Using Amino Acid Derivatives as Chiral Proton Sources.
Org Lett 2006;
8:1721-4. [PMID:
16597150 DOI:
10.1021/ol0603007]
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Abstract
[reaction: see text] Asymmetric protonation of lithium enolates was examined using commercially available amino acid derivatives as chiral proton sources. Among the amino acid derivatives tested, Nbeta-l-aspartyl-l-phenylalanine methyl ester was found to cause significant asymmetric induction in the protonation of lithium enolates. The enantiomeric excess (up to 88% ee) of the products obtained in the presence of a catalytic amount of the chiral proton source was higher than those obtained in the stoichiometric reaction.
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