Saponification of the ethoxyl group in the side chain at 4-position of the pyrrolidine compound (XIV-i) with 48% hydrobromic acid to the alcohol (XVI), followed by esterification and N-ethoxycarbonylation afforded (XVIII). Treatment of (XVIII) with phosphorus tribromide to (XIX) and vacuum distillation gave the isopropenyl compound (XX) and its saponification with potassium hydroxide afforded DL-α-kainic acid (XXI). Optical resolution of this compound with l-ephedrine gave two optical isomers one of which was entirely identical with the natural L-α-kainic acid. The other was its antipode, D-α-kainic acid.
