CU(I) ASSISTED RADIOIODINATION OF HIPPURAN WITH NO CARRIER ADDED I-131

A study on the labeling of hippuran with no-carrier I-131, assisted by Cu(I) and excess of ascorbic acid is described. The rote of ascorbic acid is to prevent the oxidation of Cu(I) to Cu(II) which activates the hydrolysis of o-iodohippuric acid to o-iodobenzoic acid. The use of Cu(I) allows an almost quantitative (97-99%) labeling yield to be obtained within 10-15 minutes at 100-degrees-C. The reaction is assumed to take place via the formation of an organocopper complex favoring the exchange reaction between radioiodine and inactive iodine in the hippuran molecule. The activation energy of the reaction was calculated to be E = 12.2 kcal/mol.