Labeling and Natural Post-Translational Modification of Peptides and Proteins via Chemoselective Pd-Catalyzed Prenylation of Cysteine

[Image: see text] The prenylation of peptides and proteins is an important post-translational modification observed in vivo. We report that the Pd-catalyzed Tsuji–Trost allylation with a Pd/BIPHEPHOS catalyst system allows the allylation of Cys-containing peptides and proteins with complete chemoselectivity and high n/i regioselectivity. In contrast to recently established methods, which use non-native connections, the Pd-catalyzed prenylation produces the natural n-prenylthioether bond. In addition, a variety of biophysical probes such as affinity handles and fluorescent tags can be introduced into Cys-containing peptides and proteins. Furthermore, peptides containing two cysteine residues can be stapled or cyclized using homobifunctional allylic carbonate reagents.