We describe a modular activation strategy for cyclopropene–tetrazine ligation. This activation strategy uses chemically diverse enzyme‐ or photolabile protecting groups as cyclopropene reactivity cages. The linkages between the caging groups and cyclopropene are through carbamates, thus permitting the application of diverse cages to allow bioorthogonal reactivity by administering enzymes or light.

Activatable cyclopropenes are unreactive toward their inverse electron demand Diels–Alder reaction partner (e.g., s-tetrazines) until they are activated. The activation strategy is highly modular due to the cyclopropene’s ability to be caged by various light- and enzyme-activatable groups. This work describes the next generation of activatable cyclopropenes with a new core scaffold that maintains the activation modularity of the first generation but improves upon the ligation kinetics with s-tetrazines by ≤270-fold.

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