Metal chelates of dl-penicillamine

Abstract

Other investigators have reported that the administration of penicillamine (β,β-dimethylcysteine) to patients with Wilson's disease results in a marked urinary excretion of Cu. Also, the toxic effects of Hg and Pb are reduced by treatments with penicillamine. These observations suggest that penicillamine has an exceptional ability to bind with metals. Hence, in the present investigation, the formation constants of penicillamine chelates were determined by the potentiometric titration method of Bjerrum. Affinity of bivalent metals for penicillamine results in the following decreasing order: Hg > Ni > Cu > Zn > Cd > Pb. The over-all formation constants (log K 1 K 2) for the 2:1 chelates for Hg, Ni, and Cu are 23.5, 22.3, and 21.7, respectively, placing penicillamine among the most potent chelating agents for the heavier metals. The structure of the chelates was deduced as a combination of the metal between the NH 2 and SH groups as is the case with cysteine.