Simple Synthesis of Ruthenium π Complexes of Aromatic Amino Acids and Small Peptides

The interaction of Ru(η⁶‐C₁₀H₈)(Cp)]⁺ (Cp=C₅H₅) with aromatic amino acids (L ‐phenylalanine, L ‐tyrosine, L ‐tryptophane, D ‐phenylglycine, and L ‐threo‐3‐phenylserine) under visible‐light irradiation gives the corresponding Ru(η⁶‐amino acid)(Cp)]⁺ complexes in near‐quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non‐aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex Ru(η⁶‐C₁₀H₈)(Cp)]⁺ was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.