Modular Enzyme- and Light-Based Activation of Cyclopropene-Tetrazine Ligation.

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.