摘要:
The diketopiperazine suggested to be the intermediate during the spontaneous isomerization of beta-ODAP and alpha-ODAP was synthesized. Its behaviour was studied at selected pH values and provided evidence that its natural occurrence is unlikely. 2-Hydroxy-imidazolidine-2,4-dicarboxylic acid (for the rearrangement beta-ODAP <---->alpha-ODAP) or 2-hydroxy-pyrimidine-2,4-dicarboxylic acid (for the rearrangement gamma-ODAB <---->alpha-ODAB) are suggested to be the unstable intermediates.