Regioselective iodination of tyrosine in a liquid membrane system, in the presence of crown ether type macrocyclic ligands. III. Comparative study onthe performance of some macrocyclic ligands and interferences of other amino acids

Continuing the study on tyrosine iodination in a liquid membrane system (aq ueous phase source containing KI + I-2 reversible arrow KI3, aqueous receiv ing phase Containing tyrosine, dichloroethanic membrane containing a macroc yclic ligand) we concluded that macrocycles benzo-18-crown-6 (B18C6), 4'-ni tro-benzo-18-crown-6 (4'-O(2)NB18C6), dicyclohexyl-18-crown-6 (DCH18C6), de cyl-18-crown-6 (D18C6) and valinomycin may be used as carriers for the iodi nating species. Tyrosine conversion to the monoiododerivative was approxima tely 30-60%, depending on the macrocyclic ligand. The interference of other essential amino acids (phenylalanine, tryptophan, histidine, valine, cyste ine, methionine) in such a process was noticed only for tryptophan and cyst eine (which are oxidized).