(~)-15-(4-Azidobenzyl) carazolol (2), a potent@-adrenergic photoaffinity ligand developed in our laboratories, has been radioiodinated to theoretical specific activity (2175 Cifmmol) and shown to label covalently@-adrenergic receptor peptides in avian and amphibian erythrocyte membrane preparations. The radioiodinated analogues of the desired compound (2) were optimally prepared by two synthetic steps from (A)-15-(4-aminobenzyl ...