Facile synthesis of bis(hydroxamamide)-based tetradentate ligands for 99mTc-radiopharmaceutical

A facile, two-step synthesis of the bis(hydroxamamide)-based tetradentate ligands for 99mTc-radiopharmaceuticals is described. Firstly, the hydroxamamide was converted to hydroximic acid chloride by reaction with sodium nitrite in hydrochloric acid at 0 °C. Secondly, treating the halide with the ethylenediamine or 1,3-propylenediamine in absolute ethanol formed the desired products, N,N′-ethylene bis(1-(4-nitroimidazole-1-yl)-propan-hydroxyiminoamide) (I) and N,N′-propylene bis(1-(4-nitroimidazole-1-yl)-propanhydroxyiminoamide) (II). The corresponding 99mTc complexes showed high yields and were found by paper electrophoresis to be electrically neutral under physiological conditions. The partition coefficients indicated a distinct difference between the two complexes.