US EPA

4754047 

Journal Article 

Metal Substitution Modulates the Reactivity and Extends the Reaction Scope of Myoglobin Carbene Transfer Catalysts 

Sreenilayam, G; Moore, EJ; Steck, V; Fasan, R 

2017 

1 

Advanced Synthesis & Catalysis
ISSN: 1615-4150
EISSN: 1615-4169 

359 

12 

2076-2089 

English 

29606929 

10.1002/adsc.201700202 

WOS:000403567500007 

Engineered myoglobins have recently emerged as promising scaffolds for catalyzing carbene-mediated transformations. In this work, we investigated the effect of altering the metal center and its first-sphere coordination environment on the carbene transfer reactivity of myoglobin. To this end, we first established an efficient protocol for the recombinant expression of myoglobin variants incorporating metalloporphyrins with non-native metals, including second- and third-row transition metals (ruthenium, rhodium, iridium). Characterization of the cofactor-substituted myoglobin variants across three different carbene transfer reactions (cyclopropanation, N-H insertion, S-H insertion) revealed a major influence of the nature of metal center, its oxidation state and first-sphere coordination environment on the catalytic activity, stereoselectivity, and/or oxygen tolerance of these artificial metalloenzymes. In addition, myoglobin variants incorporating manganese- or cobalt-porphyrins were found capable of catalyzing an intermolecular carbene C-H insertion reaction involving phthalan and ethyl α-diazoacetate, a reaction not supported by iron-based myoglobins and previously accessed only using iridium-based (bio)catalysts. These studies demonstrate how modification of the metalloporphyrin cofactor environment provides a viable and promising strategy to enhance the catalytic properties and extend the reaction scope of myoglobin-based carbene transfer catalysts.