H-3-LABELING AND C-14-LABELING OF THE AROMATASE INHIBITOR ZK-138723

Synthesis of the H-3- and C-14-labelled aromatase inhibitor ZK138723 i s described(+). The H-3-label was obtained by dehalogenation of a 4,5- diiodoimidazole derivative with tritium gas, yielding 30.8 mCi with a specific activity of 33.4 Ci/mmol. Bromine replacement in the thiophen e a-position by [C-14]cyanide afforded 25.9 mCi of the C-14-labelled m aterial with a specific activity of 55.6 mCi/mmol.