Palladium(II) pincer complexes of α-amino acids: towards the synthesis of catalytically active artificial peptides

NCN palladium(II) complexes have been covalently attached to the N- and C-termini of l-valine and to the N-terminus of the dipeptide l-Phe-l-Val-OMe. Remarkably, the hydrolysis of the NCN-Pd(II) l-Val-OMe compound afforded the corresponding palladated, free amino acid without affecting the metal site. This deprotected amino acid could be coupled to any protein, enzyme or peptidic chain by simple peptide chemistry. These bioorganometallic systems were active as catalysts in the aldol reaction between methyl isocyanate and benzaldehyde.