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

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 step-economy, 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.

Oxidation-Induced Protein Cross-Linking in Mammalian Cells.

A proximity-enabled protein cross-linking strategy with additional spatiotemporal control is highly desirable. Here, we report an oxidation-induced protein cross-linking strategy involving the incorporation of a vinyl thioether group into proteins in both and mammalian cells via genetic code expansion. We demonstrated that vinyl thioether can be selectively induced by exogenously added oxidant or by reactive oxygen species from the cellular environment, as well as by photocatalysts, and converted into a Michael acceptor, enabling fluorescence labeling and protein cross-linking.