Asymmetric Eschenmoser−Claisen Rearrangement for Anti-β-Substituted γ,δ-Unsaturated Amino Acids

Optically active anti-β-substituted γ,δ-unsaturated amino acids are important synthetic building blocks in organic synthesis and for peptidomimetics. A novel asymmetric Eschenmoser−Claisen rearrangement with use of a C₂-symmetric chiral auxiliary was developed to generate this type of amino acid. Excellent diastereoselectivities and high enantioselectivities (87−93% ee) were obtained after the chiral auxiliary was removed via iodolactonization/zinc reduction.