Chiral Bioelectrocatalytic Oxidations Driven By Electrocatalytic Oxygen Reduction and Horseradish Peroxidase or Cytochrome P450

Biocatalysis, the use of enzymes for synthesis, has emerged as a powerful tool for synthesis of chiral molecules in pharmaceutical and fine chemical industries. Natural enzymes offer inherent stereoselectivity, making them attractive catalysts for this purpose. Peroxidases and cytochrome P450s enzymes utilize an iron-heme cofactor to perform a diverse array of chemical transformations including CH 2 hydroxylation, epoxidations, and sulfur-oxidations. Here, we report chiral biocatalytic oxidations in microemulsion media driven by horseradish peroxidase (HRP) coupled with a synthetic Cu 2+ -polymer electrocatalyst to convert O 2 to H 2 O 2 . This tandem system uses crosslinked layer-by-layer (LBL) films of polyelectrolytes with Cu 2+ - poly(2-hydroxy-3-dipicolylamino) propyl methacrylate (Py-PGMADPA) to drive O 2 reduction. Peroxide in turn activates HRP crosslinked in LbL films on magnetic beads (MB) to biocatalytically oxidize styrene, ethylbenzene, and methyl phenylacetate to chiral products. R-stereoisomers of these reactants were selectively formed with a high enantiomeric excess of > 80%. Conductive microemulsion reaction media are used to provide solubility to the non-polar reactants and water to hydrate the enzymes to function. The enzyme films show high thermal stability and high chiral selectivity up to 90 °C. A second synthetic goal was to compare chiral products of reactions catalyzed by cyt P450’s natural catalytic pathway mimicked by electrocatalysis versus via electrochemical generation of H 2 O 2 . We immobilized baculosome-P450s in LBL films with polystyrene sulfonate for the natural catalytic pathway, and for peroxide activation crosslinked P450 LbL on magnetic beads. These synthetic hybrid approaches open new doors to designing biocatalytic syntheses using an electrochemical driving force.