Multifunctional Clickable Reagents for Rapid Bioorthogonal Astatination and Radio‐Crosslinking

In the past decade, several developments have expanded the chemical toolbox for astatination and the preparation of (211)At‐labeled radiopharmaceuticals. However, there is still a need for advanced methods for the synthesis of astatinated (bio)molecules to address challenges such as limited in vivo stability. Herein, we report the development of multifunctional (211)At‐labeled reagents that can be prepared by applying a modular and versatile click approach for rapid assembly. The introduction of tetrazines as bioorthogonal tags enables rapid radiolabeling and radio‐crosslinking, which is demonstrated by steric shielding of (211)At to significantly increase label stability in human blood plasma.