Palladium-Catalyzed C(sp³)–H Arylation and Alkynylation of Peptides Directed by Aspartic Acid (Asp)

Modification of the aliphatic residues without an apparent functional handle has attracted broad attention, and the scientists anticipate that the C­(sp³)–H functionalizations could be an enabling tool for peptide modifications. Among them, C­(sp³)–H functionalizations directed by endogenous peptides need to be further developed. Herein, we employed natural Asp as an endogenous directing group (DG) in the late-stage C­(sp³)–H arylation and alkynylation of peptide sequences containing l- and d-alanines (Ala) to access the desired peptide sequences containing unnatural amino acids, such as tyrosine (Tyr) analogues, phenylalanine (Phe) analogues, and alkynylated Ala analogues. Moreover, this reaction was performed very well under a mild condition (50 °C), providing 60 modified peptides in moderate to excellent yields (41–86%). Therefore, using this protocol, strongly fluorescent boron dipyrromethene (BODIPY)-labeled peptides can be successfully constructed.