Monofunctionalization of Calix[4]arene Tetracarboxylic Acid at the Upper Rim with Isothiocyanate Group: First Bifunctional Chelating Agent for Alpha-Emitter Ac-225.

A procedure is reported for synthesizing a novel, water-soluble bifunctional chelating agent derived from calix[4]arene. This chelate features tetracarboxylic acid groups at the lower rim as an actinium-225 ionophore, and an isothiocyanate functional group at the upper rim for labeling of the N-terminus of monoclonal antibodies through thiourea linkage.