Synthesis of Chemoproteomic Photoaffinity Probes via Sequential Azidation/Staudinger Ligation from Alcohols and a Benzylic C–H bond

A versatile Staudinger ligation strategy is reported for the efficient synthesis of chemoproteomic photoaffinity labeling (PAL) probes from alcohols and benzylic C-H bonds via sequential azidation and Staudinger ligation. This method leverages ubiquitous alcohols and inert C-H bonds as reaction handles for late-stage probe modification, significantly expanding the chemical space accessible for PAL probe development. The method demonstrates a broad substrate scope across structurally diverse pharmaceuticals and natural products, enabling streamlined access to PAL probes that are otherwise challenging to obtain using conventional approaches. The resulting probes successfully label protein targets in gel-based imaging studies, underscoring their utility in chemoproteomic applications.