A series of new linear photoactivatable and iodinatable antagonists of the neuropeptidic hormone vasopressin was designed and synthesized by a combination of PyBOP-mediated Boc/solid-phase peptide synthesis and solution synthesis approaches. These were based on modifications of a previously reported potent and selective antagonist of the vasopressor response (VI, receptor) to [argininelvasopressin, phenylacetyl-~-Tyr (Me)-Phe-Gln-Asn- ...