Arnold, F.H.

J. Am. Chem. Soc. 2019, 141, 19585-19588, 10.1021/jacs.9b11608

Transition-metal catalysis is a powerful tool for the construction of chemical bonds. Here we show that Pseudomonas savastanoi ethylene-forming enzyme, a non-heme iron enzyme, can catalyze olefin aziridination and nitrene C−H insertion, and that these activities can be improved by directed evolution. The nonheme iron center allows for facile modification of the primary coordination sphere by addition of metalcoordinating molecules, enabling control over enzyme activity and selectivity using small molecules.

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.

Tiller, J.C.

ChemBioChem 2015, 16, 83-90, 10.1002/cbic.201402339

Count Os in: We report organosoluble artificial metalloenzymes, generated from poly(2‐methyl‐oxazoline) enzyme conjugates and osmate as a promising new catalytic system for the dihydroxylation of alkenes in organic media.

Salmain, M.

Eur. J. Inorg. Chem. 2018, 2018, 1383-1393, 10.1002/ejic.201701359

Biohybrid catalysts resulting from the dative anchoring of half‐sandwich organometallic complexes [M(arene)(H2O)x(Cl)y]n+ (M = RuII, arene = η6‐benzene, p‐cymene or mesitylene; M = IrIII, RhIII, arene = η5‐Cp*; x = 1–3, y = 0–2, n = 0–2) to bovine beta‐lactoglobulin (βLG) or hen egg white lysozyme showed unprecedented behaviour. These constructs were shown to catalyse the asymmetric transfer hydrogenation of aryl ketones in water with sodium formate as hydrogen donor at a much faster rate than the complexes alone. Full conversion of the benchmark substrate 2,2,2‐trifluoroacetophenone was reached with an ee of 86 % for the most selective biohybrid. Surprisingly, even the crude biohybrid gave a good ee despite the presence of non‐protein‐bound metal species in the reaction medium. Other aryl ketones were reduced in the same way, and the highest ee was obtained for ortho‐substituted acetophenone derivatives. Furthermore, treatment of βLG with dimethyl pyrocarbonate resulted in a noticeable decrease of the activity and selectivity of the biohybrid, indicating that the sole accessible histidine residue (His146) was probably involved in the coordination and activation of Ru(benzene). This work underscores that protein scaffolds are efficient chiral ligands for asymmetric catalysis. The use of sodium formate instead of dihydrogen makes this approach safe, inexpensive and environmentally friendly.

Fontecilla-Camps, J.C.

Eur. J. Inorg. Chem. 2013, 2013, 3596-3600, 10.1002/ejic.201300592

The crystal structure of bovine β‐lactoglobulin bound to a complex consisting of a (η5‐Cp*)Rh(2,2′‐dipyridylamine) head and a lauric acid derived hydrophobic tail has been solved at 1.85 Å resolution. Previous work has shown that this hybrid catalyzes the transfer hydrogenation of an aryl ketone in neat water with formate as hydrogen donor with enantiomeric excess (ee) of about 26 %. Calculations using the X‐ray model indicate that the complex head can adopt discrete conformations, which may explain the ee observed.