Late‐Stage Synthesis of Photoaffinity Labeling Probes via Photochemical Minisci Chemistry

Photoaffinity labeling is an integral technique in drug development for identifying the biological targets of drug-like molecules. An essential step in this process is the design and synthesis of photocrosslinking probe molecules that contain the key biologically active warhead of the parent molecule, a photo-activatable functional group, and a biorthogonal handle. These components collectively allow for the covalent linkage of the drug to its target and subsequent isolation of the drug-protein conjugate. Current strategies to synthesize probes from their parent molecules rely on previously installed functional groups or a redesigned synthesis. Here, we report the late-stage synthesis of photoaffinity labeling probes using photochemical Minisci chemistry, where we can convert a variety of medicinally relevant aromatic N-heterocycles to their corresponding photo-crosslinking probes in a single step. Furthermore, employing our method, we synthesized photoaffinity labeling probe analogs of pioglitazone, a known peroxisome proliferator-activated receptor gamma (PPARγ) agonist. We performed photo-crosslinking and pull-down experiments to validate the target of pioglitazone, showcasing the utility of this method.