Synthesis of anti-β-substituted γ,δ-unsaturated amino acids via Eschenmoser-Claisen rearrangement

(Chemical Equation Presented) Anti-β-substituted γ,δ- unsaturated amino acids have been synthesized via a novel design of the Eschenmoser-Claisen rearrangement. The rearrangement gives good isolated yields and excellent diastereoselectivity due to (Z)-N,O-ketene acetal formation and the pseudochairlike conformations of the reaction intermediates. Upon reductive hydrolysis, important novel amino acids and amino alcohols were synthesized for the first time via this methodology.