(η6-Arene) ruthenium(ii) complexes and metallo-papain hybrid as Lewis acid catalysts of Diels–Alder reaction in water

Abstract

Covalent embedding of a (eta(6)-arene) ruthenium(II) complex into the protein papain gives rise to a metalloenzyme displaying a catalytic efficiency for a Lewis acid-mediated catalysed Diels-Alder reaction enhanced by two orders of magnitude in water.

Metal‐Conjugated Affinity Labels: A New Concept to Create Enantioselective Artificial Metalloenzymes

“…Conversion with the ruthenium-based m-ALs 1 Ru and 2 Ru also resulted in selective 1:1 addition, yet the observed masses ( 1 Ru : Δ M =420 Da, 2 Ru : Δ M =401 Da) suggest dissociation of the arene–Ru bond. Because η 6 - arene–Ru complexes were shown to be stable under similar reaction conditions,19b, 24, 27 and because we observed hydrogenation activity with asymmetric induction for the corresponding OMEHs, we assume that the observed dissociation results from the instability of the arene–Ru moiety under laser irradiation during MALDI-TOF measurements. While such complexes were observed by MALDI-MS, their decomposition in solution and solid state is documented 28.…”

Bioinspired Catalyst Design and Artificial Metalloenzymes

“…Recently Salmain and co-workers attached an h 6 -arene ruthenium phenantroline complex to papain (Scheme 17 c). [97] The obtained artificial metalloenzyme showed a significant rate enhancement in the Diels-Alder reaction between cyclopentadiene and acrolein, but no ee was observed.…”

Synthesis, Characterization and Luminescence Properties of Dipyridin‐2‐ylamine Ligands and Their Bis(2,2′‐bipyridyl)ruthenium(II) Complexes and Labelling Studies of Papain from Carica papaya

“…[20] The particular folding of papain together with the presence of a reactive cysteine makes it an interesting protein to construct artificial metalloen-zymes. [10,21] Any chemical modification of Cys25 will abolish papain's hydrolytic activity, making it easy to monitor the kinetics of its reaction with alkylating agents. In a typical experiment, papain was incubated with the maleimides in large excess (i.e., under pseudo-first-order rate conditions), and the hydrolytic activity of the mixtures was periodically measured on the chromogenic substrate PFLNa.…”

“…[9] Subsequently, one of the resulting metallopapain derivatives was shown to catalyse a Diels-Alder reaction in aqueous medium at low catalyst loading. [10] In order to gain further insight into the interaction between papain and these complexes once they are bound to the active site, we synthesized other dpa complexes of Ru II , namely [Ru(bpy) 2 (1a-b)](PF 6 ) 2 (3a-b), with potentially useful photophysical properties {the [(η 6 -arene)Ru(1a-b)Cl]Cl complexes have no particular physicochemical properties that could be exploited for this purpose}. The molecular structures of three complexes were solved by X-ray crystallography.…”