Potential diagnostic and therapeutic agents for malignant melanoma: Synthesis of heavy radiohalogenated derivatives of methylene blue by electrophilic and nucleophilic methods

Heavy radiohalogenated derivatives of methylene blue of potential value as possible diagnostic and endoradiotherapeutic agents for malignant melanoma, have been synthesized by both electrophilic and nucleophilic reaction routes. Thermal halogen isotope exchange in molten crown ether catalyst facilitated the rapid preparation of high specific activity radioiodinated and ²¹¹At]-astatinated derivatives; radiochemical yields were in the order of 60–79%. Radiohalogenation mediated by chloramine-T or via diazonium intermediary proved more laborious, far less efficient and inappropriately is only suited to the preparation of low specific activity product.