Fluorogenic Diversification of Unprotected Bromotryptophan by Aqueous Mizoroki–Heck Cross‐Coupling

Fluorescent styryl‐tryptophans have been synthesized by a Mizoroki–Heck cross‐coupling from unprotected bromotryptophan in aqueous medium showing promising spectrophotometric properties for possible application in fluorescence labelling of biomolecules. Moreover, this strategy permits a modular combination of biocatalytic halogenation by using immobilized FAD‐dependent tryptophan halogenases and Pd‐mediated chemocatalysis in a multistep one‐pot process. Light up! Fluorogenic Mizoroki–Heck cross‐coupling between bromotryptophan and styrene derivatives in aqueous medium provides fluorescently labelled tryptophan derivatives (see scheme).