Electrophilic Sulfonium-Promoted Peptide and Protein Amidation in Aqueous Media

A novel
amidation strategy using electrophilic sulfonium, which
is soluble and stable in aqueous conditions, was developed. The sulfoniums
could activate thioacid and carboxyl acid to efficiently react with
amines to afford amides. This method enables applications in amidation
in both aqueous media and solid-phase peptide synthesis, peptide/protein
modifications, and reactive lysines of a proteome at pH 10 with activity-based
protein profiling. A peptide ligand-directed labeling of the USP7–UBL2
domain was also performed using this method.