Abstract
The synthesis of [Sar1, Val5, (4′‐azido‐3′,5′‐ditritio)Phe8] angiotensin II from a iodinated precursor peptide is described. The principal problems of this synthesis and their resolution are discussed: (i) The β‐induced autophotolysis of the highly tritiated (73 Ci/mmol) and photosensitive label, and (ii) the absorption problems encountered during the purification of microgramm quantities. Such photoaffinity labels are being used for specific labeling and isolation of peptide hormone receptors.