Photoreversible prodrugs and protags: switching the release of maleimides by using light under physiological conditions.

A water-soluble furyl-substituted diarylethene derivative has been prepared that can undergo reversible Diels-Alder reactions with maleimides to yield photoswitchable Diels-Alder adducts. Employing bioorthogonal visible light, the release of therapeutically effective concentrations of maleimide-based reactive inhibitors or labels from these "prodrugs" or "protags" could be photoreversibly triggered in buffered, aqueous solution at body temperature. It is shown how the release properties can be fine-tuned and a thorough investigation of the release dynamics is presented. Our system should allow for spatiotemporal control over the inhibition and labeling of specific protein targets and is ready to be surveyed in living organisms.