Albumin-Conjugated Corrole Metal Complexes: Extremely Simple Yet Very Efficient Biomimetic Oxidation Systems
J. Am. Chem. Soc. 2005, 127, 2883-2887, 10.1021/ja045372c
An extremely simple biomimetic oxidation system, consisting of mixing metal complexes of amphiphilic corroles with serum albumins, utilizes hydrogen peroxide for asymmetric sulfoxidation in up to 74% ee. The albumin-conjugated manganese corroles also display catalase-like activity, and mechanistic evidence points toward oxidant-coordinated manganese(III) as the prime reaction intermediate.
Ligand type: CorroleHost protein: Bovine serum albumin (BSA)Reaction: SulfoxidationMax TON: 8ee: 74PDB: ---Notes: ---
Ligand type: CorroleHost protein: Bovine serum albumin (BSA)Reaction: SulfoxidationMax TON: 42ee: 52PDB: ---Notes: ---
Aqueous Oxidation of Alcohols Catalyzed by Artificial Metalloenzymes Based on the Biotin–Avidin Technology
J. Organomet. Chem. 2005, 690, 4488-4491, 10.1016/j.jorganchem.2005.02.001
Based on the incorporation of biotinylated organometallic catalyst precursors within (strept)avidin, we have developed artificial metalloenzymes for the oxidation of secondary alcohols using tert-butylhydroperoxide as oxidizing agent. In the presence of avidin as host protein, the biotinylated aminosulfonamide ruthenium piano stool complex 1 (0.4 mol%) catalyzes the oxidation of sec-phenethyl alcohol at room temperature within 90 h in over 90% yield. Gel electrophoretic analysis of the reaction mixture suggests that the host protein is not oxidatively degraded during catalysis.
Max TON: 200ee: ---PDB: ---Notes: ---
Host protein: Avidin (Av)Max TON: 230ee: ---PDB: ---Notes: ---
Ligand type: Bipyridine; C6Me6Max TON: 173ee: ---PDB: ---Notes: ---
Ligand type: Amino-sulfonamide; Cp*Max TON: 7.5ee: ---PDB: ---Notes: ---
Metal: IrLigand type: Bipyridine; Cp*Max TON: 30ee: ---PDB: ---Notes: ---
Artificial Metalloenzymes Based on Biotin-Avidin Technology for the Enantioselective Reduction of Ketones by Transfer Hydrogenation
Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 4683-4687, 10.1073/pnas.0409684102
Most physiological and biotechnological processes rely on molecular recognition between chiral (handed) molecules. Manmade homogeneous catalysts and enzymes offer complementary means for producing enantiopure (single-handed) compounds. As the subtle details that govern chiral discrimination are difficult to predict, improving the performance of such catalysts often relies on trial-and-error procedures. Homogeneous catalysts are optimized by chemical modification of the chiral environment around the metal center. Enzymes can be improved by modification of gene encoding the protein. Incorporation of a biotinylated organometallic catalyst into a host protein (avidin or streptavidin) affords versatile artificial metalloenzymes for the reduction of ketones by transfer hydrogenation. The boric acid·formate mixture was identified as a hydrogen source compatible with these artificial metalloenzymes. A combined chemo-genetic procedure allows us to optimize the activity and selectivity of these hybrid catalysts: up to 94% (R) enantiomeric excess for the reduction of p-methylacetophenone. These artificial metalloenzymes display features reminiscent of both homogeneous catalysts and enzymes.
Ligand type: Amino-sulfonamide; P-cymeneReaction: Transfer hydrogenationMax TON: 92ee: 94PDB: ---Notes: ---
Reaction: Transfer hydrogenationMax TON: 30ee: 63PDB: ---Notes: ---
Artificial Metalloenzymes for Enantioselective Catalysis Based on the Noncovalent Incorporation of Organometallic Moieties in a Host ProteinReview
Chem. - Eur. J. 2005, 11, 3798-3804, 10.1002/chem.200401232
Enzymatic and homogeneous catalysis offer complementary means to produce enantiopure products. Incorporation of achiral, biotinylated aminodiphosphine–rhodium complexes in (strept)avidin affords enantioselective hydrogenation catalysts. A combined chemogenetic procedure allows the optimization of the activity and the selectivity of such artificial metalloenzymes: the reduction of acetamidoacrylate proceeds to produce N‐acetamidoalanine in either 96 % ee (R) or 80 % ee (S). In addition to providing a chiral second coordination sphere and, thus, selectivity to the catalyst, the phenomenon of protein‐accelerated catalysis (e.g., increased activity) was unraveled. Such artificial metalloenzymes based on the biotin–avidin technology display features that are reminiscent of both homogeneous and of enzymatic catalysis.
Artificial Metalloenzymes: Proteins as Hosts for Enantioselective CatalysisReview
Chem. Soc. Rev. 2005, 34, 337, 10.1039/b314695m
Enantioselective catalysis is one of the most efficient ways to synthesize high-added-value enantiomerically pure organic compounds. As the subtle details which govern enantioselection cannot be reliably predicted or computed, catalysis relies more and more on a combinatorial approach. Biocatalysis offers an attractive, and often complementary, alternative for the synthesis of enantiopure products. From a combinatorial perspective, the potential of directed evolution techniques in optimizing an enzyme's selectivity is unrivaled. In this review, attention is focused on the construction of artificial metalloenzymes for enantioselective catalytic applications. Such systems are shown to combine properties of both homogeneous and enzymatic kingdoms. This review also includes our recent research results and implications in the development of new semisynthetic metalloproteins for the enantioselective hydrogenation of N-protected dehydro-amino acids.
Chemical Optimization of Artificial Metalloenzymes Based on the Biotin-Avidin Technology: (S)-Selective and Solvent-Tolerant Hydrogenation Catalysts via the Introduction of Chiral Amino Acid Spacers
Chem. Commun. 2005, 4815, 10.1039/b509015f
Incorporation of biotinylated-[rhodium(diphosphine)]+ complexes, with enantiopure amino acid spacers, in streptavidin affords solvent-tolerant and selective artificial metalloenzymes: up to 91% ee (S) in the hydrogenation of N-protected dehydroamino acids.
Optimization: ChemicalMax TON: ---ee: ---PDB: ---Notes: ---
Coordinated Design of Cofactor and Active Site Structures in Development of New Protein Catalysts
J. Am. Chem. Soc. 2005, 127, 6556-6562, 10.1021/ja045995q
New methods for the synthesis of artificial metalloenzymes are important for the construction of novel biocatalysts and biomaterials. Recently, we reported new methodology for the synthesis of artificial metalloenzymes by reconstituting apo-myoglobin with metal complexes (Ohashi, M. et al., Angew Chem., Int. Ed.2003, 42, 1005−1008). However, it has been difficult to improve their reactivity, since their crystal structures were not available. In this article, we report the crystal structures of MIII(Schiff base)·apo-A71GMbs (M = Cr and Mn). The structures suggest that the position of the metal complex in apo-Mb is regulated by (i) noncovalent interaction between the ligand and surrounding peptides and (ii) the ligation of the metal ion to proximal histidine (His93). In addition, it is proposed that specific interactions of Ile107 with 3- and 3‘-substituent groups on the salen ligand control the location of the Schiff base ligand in the active site. On the basis of these results, we have successfully controlled the enantioselectivity in the sulfoxidation of thioanisole by changing the size of substituents at the 3 and 3‘ positions. This is the first example of an enantioselective enzymatic reaction regulated by the design of metal complex in the protein active site.
Ligand type: SalophenMax TON: ---ee: ---PDB: 1V9QNotes: ---
Metal: CrLigand type: SalophenMax TON: ---ee: ---PDB: 1J3FNotes: ---
Ligand type: SalenMax TON: ---ee: ---PDB: ---Notes: ---
Metal: CrLigand type: SalenMax TON: ---ee: ---PDB: ---Notes: ---
Design of Artificial MetalloenzymesReview
Appl. Organomet. Chem. 2005, 19, 35-39, 10.1002/aoc.726
Homogeneous and enzymatic catalysis offer complementary means to generate enantiomerically pure compounds. For this reason, in a biomimetic spirit, efforts are currently under way in different groups to design artificial enzymes. Two complementary strategies are possible to incorporate active organometallic catalyst precursors into a protein environment. The first strategy utilizes covalent anchoring of the organometallic complexes into the protein environment. The second strategy relies on the use of non‐covalent incorporation of the organometallic precursor into the protein. In this review, attention is focused on the use of semisynthetic enzymes to produce efficient enantioselective hybrid catalysts for a given reaction. This article also includes our recent research results and implications in developing the biotin–avidin technology to localize the biotinylated organometallic catalyst precursor within a well‐defined protein environment.
Merging Homogeneous Catalysis with Biocatalysis; Papain as Hydrogenation Catalyst
Chem. Commun. 2005, 5656, 10.1039/B512138H
Papain, modified at Cys-25 with a monodentate phosphite ligand and complexed with Rh(COD)2BF4, is an active catalyst in the hydrogenation of methyl 2-acetamidoacrylate.
Host protein: Papain (PAP)Anchoring strategy: CovalentOptimization: ---Max TON: 400ee: <10PDB: ---Notes: ---
Tailoring the Active Site of Chemzymes by Using a Chemogenetic-Optimization Procedure: Towards Substrate-Specific Artificial Hydrogenases Based on the Biotin–Avidin Technology
Angew. Chem. Int. Ed. 2005, 44, 7764-7767, 10.1002/anie.200502000
The combination of chemical‐ with genetic‐optimization strategies (i.e. chemogenetic) allows the production of artificial hydrogenases based on the biotin–avidin technology. In the spirit of enzymes, second‐coordination‐sphere interactions between the host protein (streptavidin) and the substrate (an olefin) allow fine‐tuning of the selectivity to produce either R or S hydrogenation products.
Max TON: ---ee: 94PDB: ---Notes: ---