Synthesis and in vitro Enzyme Hydrolysis of Trioxadiaza- and Tetraoxadiaza-Crown Ether-Based Complexing Agents with Disposable Ester Pendant Arms

New disposable ester derivatives of the complexing agents N,N'-bis(carboxymethyl)piperaizine, -homopiperazine, -1,7-diaza-15-crown-5 and -1.10-diaza-18-crown-6 were synthesized with a variety of synthetic methods and fully characterized. Hydrolytic properties of the pendant arms were studied under different pH conditions as well as in the presence and absence of porcine liver esterase enzyme and approximate hydrolysis half lives were determined by 1 H NMR technique. In vitro studies on pig liver cell homogenates and living thin chicken liver slices proved that the selected double ester 4b can penetrate liver tissues spontaneously, liberate the free complexing agent N,N'-bis(carboxymethyl)-18-ane-N 2 O 4 (ODDA) inside the cells and are potentially capable of removing lead and other toxic metal ions from the liver.