A new stereocontrolled route to (−)-kainic acid, the representative of the kainoid amino acids and exhibiting insecticidal, anthelmintic and neuroexcitatory properties, has been devised in an enantioconvergent way using either (+)- or (−)-ketodicyclopentadiene as the starting material by employing a concurrent retro-Diels-Alder reaction and intramolecular ene reaction as the keystep.