摘要:
Bis-amine bis-thiol tetraligands such as ethylene dicysteine (EC) and its diethylester (ECD) bind Tc-99m efficiently at room temperature and neutral to alkaline pH to form stable complexes. The use of bis-amine bis-thiol ligands as bifunctional chelating agents (BCAs) for labelling of bioactive compounds (peptides, diphosphonates, etc.) looks promising. To study the effect of extending the carboxylic side-group in Tc-99m-L,L-EC and Tc-99m-L,L-ECD, we have synthesised ethylene bis-L-beta-homocysteine (L,L-EC) and its diethylester derivative L,L-EhCD, incorporating a methylene group between each of the carboxyl groups and the N2S2 tetraligand core. The more distant carboxyl groups could offer reduced steric hindrance in the use of L,L-EhC and L,L-EhCD as BCAs.