Bioorthogonal fluorogenic chemistry using a light-activated tetrazine

Triggerable and fluorogenic bioorthogonal reactions are a powerful tool for a multitude of biological and materials science applications. The concepts of light-activated tetrazines and fluorogenic inverse electron-demand Diels-Alder (IEDDA) reactions have been reported independently, but herein, for the first time, these concepts are combined into a single triggerable and fluorogenic IEDDA probe. An <i>N</i>-Voc photocaged tetrazine was developed that, upon uncaging, reacted with a strained alkyne in an IEDDA to form a fluorogenic pyridazine product. In a model system, an X-ray crystal structure of a caged dihydrotetrazine confirmed the carbamate regioisomer isomer present. This work could be used in applications where spatiotemporal control of a reaction and an inherent fluorescent readout are both advantageous.