Catalytic effect of copper(II) chloride on the radioiodination of L-P-Iodo phenylalanine

The various iodo phenylalanine isomers have been used for pancreatic imaging studies. In this work a convenient method was developed for incorporating radioactive iodine onto L-P-iodo phenylalanine (p-IPA) using copper(II) chloride to promote radioiodination. Radioiodination conditions were optimized in terms of reaction time, temperature, copper(II) chloride and P-IPA concentration. Catalytic effect of other metal salts such as Mg Cl2.6 H2 O, Ni(NO3).6 H2 O, also pivalic acid and acetamide as a molten solvent were tested. Radioiodination of P-IPA with Na131 I in organic media such as dimethyl sulfoxide(DMSO), dimethyl formamide (DMF) and dioxane were achieved and a comparison was made as to the labelling rates. The rate order was found to be as follows: Dioxane>DMSO>DMF. The results showed that copper(II) chloride was effective for facilitating the exchange reaction with maximum yield (87%)after 60 min at 150 degree C. Activation energy of 13.3 k cal/mol was also determined. 11 figs., 2 tabs