Abstract β-ethoxycarbonyl β, λ-insaturated λ-lactones 2 are easily prepared by dehydration of β-acyl β-ethoxycarbonyl α-alkyl propionic acids. Otherwise the condensation of these acids with allylzinc reagents produces β-ethoxycarbonyl λ-lactones 3 with a β-ethylenic carbon chain branched on the λ-carbon of the lactone.
