THERMAL-ISOMERIZATION OF N-OXALYL DERIVATIVES OF DIAMINO ACIDS

The neurotoxic constituent of the legume Lathyrus sativus, beta-N-oxalyl-alpha,beta-diaminopropionic acid, was thermally isomerized to an equilibrium mixture (60/40) containing the non-toxic alpha-N-oxalyl-alpha,beta-diaminopropionic acid. The same equilibrium mixture was established by starting with the alpha-isomer but required longer time. alpha- and gamma-N-Oxalyl-alpha,gamma-diaminobutyric acids also underwent thermally induced isomerization with alpha-gamma, or gamma-alpha migration of the oxalyl group. Delta-N-Oxalylomithine and epsilon-N-oxalyllysine did not isomerize under these conditions. The observation that the higher homologues do not undergo isomerization suggests the intramolecular nature of the reaction.