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.

Graphical abstractThe first peptide–metal complexes based on thiazolylalanine, a close analogue of classical N-heterocyclic carbenes (NHCs) are reported and fully characterized.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► The first organometallic bioconjugates of thiazole-based peptides are reported. ► Thiazolylalanine, a close analogue of classical N-heterocyclic carbenes, is used as a ligand for Cp∗Rh and Arene-Ru fragments, which coordinate to the carbene carbon atom. ► All new compounds are comprehensively characterized spectroscopically and their mass spectra (ESI-MS or MALDI-TOF) provide characteristic isotope patterns.