Triple C–H Activation/Annulation: In Situ Construction of Fluorescent Peptides

Abstract

Herein, we report a Rh(III)-catalyzed triple C−H activation−annulation of Phe-based peptides with alkynes for the preparation of fluorescent peptides. The robustness of this protocol is reflected by a broad substrate scope, high atom-and stepeconomy, and excellent chemo-and site-selectivity. An in situ generated polycyclic aromatic hydrocarbon carbocation as a fluorophore exhibits good fluorescence properties (maximum emission wavelength up to 628 nm) and low cell cytotoxicity. The synthetic utility of this method is further demonstrated by versatile product applications in bioconjugation with the protein BSA and specifically targeting lysosomes and mitochondria of live mammalian cells.