Chemoselective Pd(0)-catalyzed peptide coupling in water.

[reaction: see text] Highly charged peptides ranging in length from 17 to 33 residues have been efficiently tricoupled to a trialkyne nucleus by using a Sonogashira Pd(0) coupling strategy under both acidic (pH 5.0) and basic (pH 7.5) conditions. These results demonstrate the utility of Pd(0) to construct protein-sized structures (12,000 mol wt) in aqueous milieu.