title: Catalytic asymmetric protonation of lithium enolates using amino acid derivatives as chiral proton sources.
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.
authors.affiliation: Graduate School of Science and Technology, Chiba University, Inage, Chiba 263-8522, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Mitsuhashi
authors.forename: Rie
authors.initials: R
authors.lastname: Ito
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Arai
authors.forename: Akira
authors.initials: A
authors.lastname: Yanagisawa
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001218:Aspartame / Q000737:chemistry*; D002384:Catalysis; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D011522:Protons; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D011522:Protons; D008094:Lithium; D001218:Aspartame