2021 Volume 79 Issue 4 Pages 311-321
Hoveyda-Grubbs-type complexes with a ruthenium center coordinated by an N-heterocyclic carbene (NHC) and a 2-alkoxybenzylidene ligands have gained increased applicative importance as catalysts for olefin metathesis because the complexes have suitable reactivities and stabilities in a wide range of reaction media. Furthermore, this type of catalysts has also been applied for biochemical research projects including the construction of artificial biocatalysts and the regulation of in-cell bioreactions because the ruthenium-olefin interaction, a driving force of olefin metathesis mediated by Hoveyda-Grubbs-type complexes, provides the specificity among functional groups in biomolecules. In this context, we have investigated the structural modification of Hoveyda-Grubbs-type complexes aiming at the application of the complexes to biomolecules. In parallel, we have also studied the mechanism of olefin metathesis in aqueous media. In this article, we firstly describe the construction of an artificial metalloenzyme with olefin metathesis activity using α-chymotrypsin. The artificial metalloenzyme displayed the substrate specificity with the protein surface charge state. Next, we demonstrate the importance of chloride anion in solutions to attain efficient olefin metathesis reactions in aqueous media and the reactivity control of Hoveyda-Grubbs-type complexes through second-coordination sphere effect. Finally, we introduce the ruthenium complex transfer reaction between Hoveyda-Grubbs-type complexes and biomolecules (peptides and proteins) through the ruthenium-olefin specific interaction. The reaction potentially serves a new type of chemical modification strategy toward biomolecules.
