Synthesis and properties of new photoactivable derivatives of tetrodotoxin.

The Pfitzner-Moffatt oxidation procedure has been used to prepare two new photoactivable derivatives of tetrodotoxin that have been synthesized with high specific radioactivities (17.5 Ci/mmol and 30 Ci/mmol). They specifically bind to axonal membranes with affinities of 5.2-14.2 nM. They dissociate from their membrane complex with half-lives of 10.8 and 20 min. In the dark, these compounds give a reversible block of the sodium channels. After ultraviolet irradiation, they induce an irreversible blockade of the nerve channels.