Biodegradable chelating agents. Effect of optical isomerism on the physicochemical characteristics

Abstract

A series of environmentally safe bioactive chelators based on racemic aspartic and glutamic acids have been obtained. In addition, an optically active L-isomer of N-(carboxymethyl) aspartic acid (L-CMA) was synthesized, and its acid-base characteristics were determined by pH-titration analysis. The detected high activity of the nitrogen atom of L-CMA (pK₄ = 10.42) is apparently due to the betainic structure of this compound in solution and formation of a cycle with an intramolecular hydrogen bond between the nitrogen atom of the protonated amino group and the oxygen atom of the water molecule included in this cycle. This hypothesis is confirmed by IR spectral analysis of the L-isomers of the parent acids.