Bioconjugation of Peptides by Palladium-Catalyzed C−C Cross-Coupling in Water

The abiotic, regioselective conjugation of peptides and proteins with non-proteinogenic structural elements requires mild and fast coupling reactions which are compatible with an aqueous reaction medium and orthogonal in their reactivity with all other functional groups in the protein. Sonogashira coupling with a palladium–guanidinophosphane catalyst that is prepared in situ (see reaction on the right) complies with these demands.