A Late-Stage Aryl C-H Olefination Strategy and Its Application Towards Global Proteome Profiling of ∆8-Tetrahydrocannabinol.

Drugs and bioactive natural products exert their pharmacological effects by engaging numerous cellular targets in our body. Identification of these protein targets is essential for understanding the mechanism-of-action of these compounds, thus contributing to improved drug design in drug discovery programs. Termed "in situ drug profiling", a common strategy for studying these bioactive compounds centralized on the covalent capture of protein targets along with a reporter tag to facilitate downstream proteomic analyses. Though highly successful, such a strategy required innate electrophilic traps to facilitate covalent capture, and its dependence on classical alkylation/acylation strategies to install reporter tags has restricted its applications on non-covalent compounds. Late-stage C-H functionalization (LSF) may resolve this by substituting biologically inert C-H bonds with desired electrophilic groups. Herein, we demonstrated this concept by arming a diverse range of electron-rich aromatic drugs and natural products with α,β-unsaturated esters, via late-stage C-H olefination with a arylthio-based carboxylic acid ligand developed by Ibanez and co-workers. We also showed that covalent probes generated from this LSF approach could be applied for "in situ drug profiling" of ∆8-THC, as exemplified by the successful target engagement of α-4db, a ∆8-THC-based probe, to its native target hCB2R. In combination with probe 7, a photoaffinity-based derivative of ∆8-THC, we identified several novel putative targets that could account for some of the effects in THC consumption. We anticipate our C-H LSF strategy to be widely adopted for future studies of non-covalent drugs.