Feasibility of isotopic exchange in the system [125I] iodide: undecahydro-iodo-closo-dodecaborate(2-) anion

Derivatives of the closo-dodecaborate dianion are routinely used or proposed for use in boron neutron capture therapy of cancer. The use of radioactive label on closo-dodecaborate might facilitate pharmacokinetic studies. The use of nucleophilic reactions might be of advantage if derivatives of closo-dodecaborate were oxidation sensitive. The aim of this study was to estimate the feasibility of isotopic exchange in radioiodide - iodo-undecahydro-closo-dodecaborate system. We demonstrated that copper-catalyzed isotope exchange in this system in molten acetamide provides a labeling yield of 78.4±1.1% after 30 minutes at 170 °C. The influence of the ratio between amounts of substrate and catalyst, temperature and time on the labeling yield was studied.