Organometallic peptide NHC complexes of Cp∗Rh(III) and arene Ru(II) moieties from l-thiazolylalanine

The 3-ethyl thiazolium peptide salts Boc-Thia-Leu-OMe and Boc-Thia-Leu-Phe-OMe based on the unnatural amino acid thiazolylalanine (Thia) have been prepared. After deprotonation, they reacted rapidly via the silver carbene transfer reaction with [RhCp∗Cl2]2 and [Ru(p-cymene)Cl2]2 to yield the corresponding thiazole-based carbene complexes 7–10 in acceptable yield. All new compounds were characterized by multinuclear NMR spectroscopy, mass spectrometry, and elemental analysis. These complexes constitute the first examples of thiazolylalanine-2-ylidene metal bioconjugates.