Various N-benzyloxycarbonyl-α-dehydroamino acid methyl esters were newly synthesized by the condensation of α-oxocarboxylic acids with benzyl carbomate followed by methyl esterfication. Others were obtained by the Wittig-Horner reaction of aldehydes with diethoxyphosphinylglycine and by the base-catalyzed β-elimination of β-acetoxy or β-halo-α-amino acids.