Near-infrared light-driven asymmetric photolytic reduction of ketone using inorganic-enzyme hybrid biocatalyst
Li Qiao (Hangzhou Normal University)
Jing Zhang (Hangzhou Normal University)
Yongjian Jiang (Hangzhou Normal University)
Bianqin Ma (Hangzhou Normal University)
Haomin Chen (Hangzhou Normal University)
Peng Gao (Hangzhou Normal University)
Pengfei Zhang (Hangzhou Normal University)
Anming Wang (Hangzhou Normal University)
Roger A. Sheldon (University of Witwatersrand, TU Delft - BT/Biocatalysis)
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Abstract
Effective photolytic regeneration of the NAD(P)H cofactor in enzymatic reductions is an important and elusive goal in biocatalysis. It can, in principle, be achieved using a near-infrared light (NIR) driven artificial photosynthesis system employing H2O as the sacrificial reductant. To this end we utilized TiO2/reduced graphene quantum dots (r-GQDs), combined with a novel rhodium electron mediator, to continuously supply NADPH in situ for aldo-keto reductase (AKR) mediated asymmetric reductions under NIR irradiation. This upconversion system, in which the Ti-O-C bonds formed between r-GQDs and TiO2 enabled efficient interfacial charge transfer, was able to regenerate NADPH efficiently in 64 % yield in 105 min. Based on this, the pharmaceutical intermediate (R)-1-(3,5-bis(trifluoromethyl)phenyl)ethan-1-ol was obtained, in 84 % yield and 99.98 % ee, by reduction of the corresponding ketone. The photo-enzymatic system is recyclable with a polymeric electron mediator, which maintained 66 % of its original catalytic efficiency and excellent enantioselectivity (99.9 % ee) after 6 cycles.