Bridgehead Alkene-Enabled Strain-Driven Bioorthogonal Reaction.

Herein, we report a novel bioorthogonal reaction that hinges on a bridgehead alkene (BHA)-enabled inverse-electron-demand Diels-Alder (IEDDA) cycloaddition. Readily accessible from natural product β-caryophyllene, the strained BHA displays high reactivity toward the IEDDA reaction while maintaining excellent biocompatibility. The developed IEDDA reaction has been applied to in vitro protein labeling and pretargeted live cell imaging.