Ring Opening of Pyrrolidonecarboxylic Acid via a Metal Chelate

Abstract

L-Pyrrolidonecarboxylic acid (PCA) is a cyclic compound derived on intramolecular dehydration of L-glutamic acid. The conventional method used for the conversion of PCA to glutamic acid has been hydrolysis with strong acids or alkalis at high temperatures. On the reaction of metallic ions such as zinc with PCA, a chelate compound of glutamic acid, and not a metallic salt of PCA, was found to precipitate. This chelate compound dissolved in a dilute mineral acid and glutamic acid crystallized out at the isoelectric point. The yield achieved with this novel direct ring opening of PCA at neutral pH reached 93.1%.