11 publications

11 publications

An Artificial Imine Reductase Based on the Ribonuclease S Scaffold

Ward, T.R.

ChemCatChem 2014, 6, 736-740, 10.1002/cctc.201300995

Dative anchoring of a piano‐stool complex within ribonuclease S resulted in an artificial imine reductase. The catalytic performance was modulated upon variation of the coordinating amino acid residues in the S‐peptide. Binding of Cp*Ir (Cp*=C5Me5) to the native active site resulted in good conversions and moderate enantiomeric excess values for the synthesis of salsolidine.


Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Ribonuclease S
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: 4
ee: 18
PDB: ---
Notes: ---

Artificial Copper Enzymes for Asymmetric Diels–AlderReactions

Kamer, P.C.J.; Laan, W.

ChemCatChem 2013, 5, 1184-1191, 10.1002/cctc.201200671

The development of artificial copper enzymes from sterol carrier protein type 2 like domain (SCP‐2L) for the use in asymmetric catalysis was explored. For this purpose, proteins were modified with various nitrogen donor ligands. Maleimide‐containing ligands were found most suitable for selective cysteine bio‐conjugation. Fluorescence spectroscopy was used to confirm copper binding to an introduced phenanthroline ligand, which was introduced in two unique cysteine containing SCP‐2L mutants. Copper adducts of several modified SCP‐2L templates were applied in asymmetric Diels–Alder reactions. A clear influence of both the protein environment and the introduced ligand was found in the asymmetric Diels–Alder reaction between azachalcone and cyclopentadiene. A promising enantioselectivity of 25 % ee was obtained by using SCP‐2L V83C modified with phenanthroline–maleimide ligand. Good endo selectivity was observed for SCP‐2L modified with the dipicolylamine‐based nitrogen donor ligand. These artificial metalloenzymes provide a suitable starting point for the implementation of various available techniques to optimise the performance of this system.


Metal: Cu
Anchoring strategy: Covalent
Optimization: Chemical & genetic
Max TON: 9.6
ee: 25
PDB: 1IKT
Notes: ---

Artificial Metalloenzymes

Review

Roelfes, G.

ChemCatChem 2010, 2, 916-927, 10.1002/cctc.201000011

Artificial metalloenzymes have emerged as a promising approach to merge the attractive properties of homogeneous catalysis and biocatalysis. The activity and selectivity, including enantioselectivity, of natural metalloenzymes are due to the second coordination sphere interactions provided by the protein. Artificial metalloenzymes aim at harnessing second coordination sphere interactions to create transition metal complexes that display enzyme‐like activities and selectivities. In this Review, the various approaches that can be followed for the design and optimization of an artificial metalloenzyme are discussed. An overview of the synthetic transformations that have been achieved using artificial metalloenzymes is provided, with a particular focus on recent developments. Finally, the role that the second coordination sphere plays in artificial metalloenzymes and their potential for synthetic applications are evaluated.


Notes: ---

Diruthenium Diacetate-Catalyzed Aerobic Oxidation of Hydroxylamines and Improved Chemoselectivity by Immobilization to Lysozyme

Cardona, F.; Goti, A.; Messori, L.

ChemCatChem 2017, 9, 4225-4230, 10.1002/cctc.201701083

A new green method for the preparation of nitrones through the aerobic oxidation of the corresponding N,N‐disubstituted hydroxylamines has been developed upon exploring the catalytic activity of a diruthenium catalyst, that is, [Ru2(OAc)4Cl]), in aqueous or alcoholic solution under mild reaction conditions (0.1 to 1 mol % catalyst, air, 50 °C) and reasonable reaction times. Notably, the catalytic activity of the dimetallic centre is retained after its binding to the small protein lysozyme. Interestingly, this new artificial metalloenzyme conferred complete chemoselectivity to the oxidation of cyclic hydroxylamines, in contrast to the diruthenium catalyst.


Metal: Ru
Ligand type: Amino acid; OAc
Host protein: Lysozyme
Anchoring strategy: Dative
Optimization: Chemical
Max TON: 1000
ee: ---
PDB: ---
Notes: ---

Evaluation of Chemical Diversity of Biotinylated Chiral 1,3-Diamines as a Catalytic Moiety in Artificial Imine Reductase

Rimoldi, I.

ChemCatChem 2016, 8, 1665-1670, 10.1002/cctc.201600116

The possibility of obtaining an efficient artificial imine reductase was investigated by introducing a chiral cofactor into artificial metalloenzymes based on biotin–streptavidin technology. In particular, a chiral biotinylated 1,3‐diamine ligand in coordination with iridium(III) complex was developed. Optimized chemogenetic studies afforded positive results in the stereoselective reduction of a cyclic imine, the salsolidine precursor, as a standard substrate with access to both enantiomers. Various factors such as pH, temperature, number of binding sites, and steric hindrance of the catalytic moiety have been proved to affect both efficiency and enantioselectivity, underlining the great flexibility of this system in comparison with the achiral system. Computational studies were also performed to explain how the metal configuration, in the proposed system, might affect the observed stereochemical outcome.


Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: >99
ee: 83
PDB: 3PK2
Notes: ---

Expanding the Chemical Diversity in Artificial Imine Reductases Based on the Biotin–Streptavidin Technology

Ward, T.R.

ChemCatChem 2014, 6, 1010-1014, 10.1002/cctc.201300825

We report on the optimization of an artificial imine reductase based on the biotin‐streptavidin technology. With the aim of rapidly generating chemical diversity, a novel strategy for the formation and evaluation of biotinylated complexes is disclosed. Tethering the biotin‐anchor to the Cp* moiety leaves three free coordination sites on a d6 metal for the introduction of chemical diversity by coordination of a variety of ligands. To test the concept, 34 bidentate ligands were screened and a selection of the 6 best was tested in the presence of 21 streptavidin (Sav) isoforms for the asymmetric imine reduction by the resulting three legged piano stool complexes. Enantiopure α‐amino amides were identified as promising bidentate ligands: up to 63 % ee and 190 turnovers were obtained in the formation of 1‐phenyl‐1,2,3,4‐tetrahydroisoquinoline with [IrCp*biotin(L‐ThrNH2)Cl]⊂SavWT as a catalyst.


Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 188
ee: 43
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Amino carboxylic acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 4
ee: 21
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Cp*; Diamine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 0
ee: ---
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 0
ee: ---
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Cp*; Pyrazine amide
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 26
ee: 16
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Bipyridine; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 0
ee: ---
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 12
ee: 13
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Cp*; Oxazoline
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 102
ee: 14
PDB: ---
Notes: ---

Metal: Ir
Ligand type: Amino acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 94
ee: 67
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Amino amide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 10
ee: 7
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Amino carboxylic acid; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 8
ee: 1
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Cp*; Diamine
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 6
ee: 1
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 6
ee: 1
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Cp*; Pyrazine amide
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 6
ee: 1
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Bipyridine; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 4
ee: 6
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 6
ee: 1
PDB: ---
Notes: ---

Metal: Rh
Ligand type: Cp*; Oxazoline
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Chemical & genetic
Max TON: 8
ee: 0
PDB: ---
Notes: ---

Fluorescence-Based Assay for the Optimization of the Activity of Artificial Transfer Hydrogenase within a Biocompatible Compartment

Ward, T.R.

ChemCatChem 2013, 5, 720-723, 10.1002/cctc.201200834

The time capsules: The transfer hydrogenation of an enone‐bound fluorogenic compound by an artificial metalloenzyme leads to the release of fluorescent compound umbelliferone. Upon encapsulation of the hybrid catalyst inside a biocompatible compartment, the activity of the transfer hydrogenase is maintained for several months, even at micromolar concentrations.


Metal: Ir
Ligand type: Amino-sulfonamide; Cp*
Host protein: Streptavidin (Sav)
Anchoring strategy: Supramolecular
Optimization: Genetic
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Iron-porphyrin Catalyzed Carbene Transfer Reactions – an Evolution fro Biomimetic Catalysis towards Chemistry-inspired Non-natural Reactivities of Enzymes

Koenigs, R.M.; Weissenborn, M.J.

ChemCatChem 2020, 10.1002/cctc.201901565

Bioinspired, synthetic porphyrin complexes are important catalysts in organic synthesis and play a pivotal role in efficient carbene transfer reactions. The advances in this research area stimulated recent, “chemo‐inspired” developments in biocatalysis. Today, both synthetic iron complexes and enzymes play an important role to conduct carbene transfer reactions. The advances and potential developments in both research areas are discussed in this concept article.


Metal: Fe
Ligand type: Porphyrin
Host protein: ---
Anchoring strategy: ---
Optimization: Chemical & genetic
Reaction: Carbene insertion
Max TON: ---
ee: ---
PDB: ---
Notes: ---

Optimization of and Mechanistic Considerations for the Enantioselective Dihydroxylation of Styrene Catalyzed by Osmate-Laccase-Poly(2-Methyloxazoline) in Organic Solvents

Tiller, J.C.

ChemCatChem 2016, 8, 593-599, 10.1002/cctc.201501083

The Sharpless dihydroxylation of styrene with the artificial metalloenzyme osmate‐laccase‐poly(2‐methyloxazoline) was investigated to find reaction conditions that allow this unique catalyst to reveal its full potential. After changing the co‐oxidizing agent to tert‐butyl hydroperoxide and optimizing the osmate/enzyme ratio, the turnover frequency and the turnover number could be increased by an order of magnitude, showing that the catalyst can compete with classical organometallic catalysts. Varying the metal in the active center showed that osmate is by far the most active catalytic center, but the reaction can also be realized with permanganate and iron(II) salts.


Metal: Os
Ligand type: Undefined
Host protein: Laccase
Anchoring strategy: Undefined
Optimization: Chemical
Reaction: Dihydroxylation
Max TON: 842
ee: > 99
PDB: ---
Notes: ---

Regioselective Hydroformylation of Styrene Using Rhodium-Substituted Carbonic Anhydrase

Kazlauskas, R.J.

ChemCatChem 2010, 2, 953-957, 10.1002/cctc.201000159

CA confidential: Replacing the active‐site zinc in carbonic anhydrase (CA) by rhodium forms a new enzymatic catalyst for cofactor‐free hydroformylation of styrene with syn gas. Unlike free rhodium, this rhodium–protein hybrid, [Rh]–CA, is regioselective (8.4:1) for linear over branched aldehyde product, which is a 40‐fold change in regioselectivity compared to free rhodium.


Metal: Rh
Ligand type: Acac; Carbonyl
Anchoring strategy: Metal substitution
Optimization: Genetic
Reaction: Hydroformylation
Max TON: 298
ee: ---
PDB: 4CAC
Notes: PDB ID 4CAC = Structure of Zn containing hCAII

Rhodium-Complex-Linked Hybrid Biocatalyst: Stereo-Controlled Phenylacetylene Polymerization within an Engineered Protein Cavity

ChemCatChem 2014, n/a-n/a, 10.1002/cctc.201301055

The incorporation of a Rh complex with a maleimide moiety into the cavity of the nitrobindin β‐barrel scaffold by a covalent linkage at the 96‐position (Cys) provides a hybrid biocatalyst that promotes the polymerization of phenylacetylene. The appropriate structural optimization of the cavity by mutagenesis enhances the stereoselectivity of the polymer with a trans content of 82 % at 25 °C and pH 8.0. The X‐ray crystal structure of one of the hybrid biocatalysts at a resolution of 2.0 Å reveals that the Rh complex is located in the β‐barrel cavity without any perturbation to the total protein structure. Crystal structure analysis and molecular modeling support the fact that the stereoselectivity is enhanced by the effective control of monomer access to the Rh complex within the limited space of the protein cavity.


Metal: Rh
Ligand type: COD; Cp*
Host protein: Nitrobindin (Nb)
Anchoring strategy: Cystein-maleimide
Optimization: Genetic
Max TON: ---
ee: ---
PDB: 3WJC
Notes: ---