Chemoenzymatic catalysis of tert-butyl 6-cyano-(3R,5R)-dihydroxyhexanoate by aldo-keto reductase coupled with composite Fe3O4 nanozyme scaffold

• A novel Fe 3 O 4 nanozyme catalyst scaffold Fe 3 O 4 @HMWCNTs has been designed and synthesized. • Fe 3 O 4 @HMWCNTs can transfer hydrogenation of NADP + to NADPH efficiently and repeatedly. • Fe 3 O 4 @HMWCNTs and natural enzyme are compatible. • Various chiral alcohols can be synthesized via Fe 3 O 4 @HMWCNTs coupled with Km AKR M7 . Cofactor NADPH is widely used in enzymatic redox reactions, however, its regeneration by glucose dehydrogenase (GDH) suffers from massive glucose consumption, costly wastewater treatment, and low atom efficiency. Herein, Fe 3 O 4 nanoparticles supported on helical multi-walled carbon nanotubes (Fe 3 O 4 @HMWCNTs) was prepared and displayed comparable transfer hydrogenation activity to Exiguobacterium sibiricum GDH ( Es GDH). We developed a chemoenzymatic catalysis based on a combination of an aldo–keto reductase Km AKR with Fe 3 O 4 @HMWCNTs scaffold, which asymmetrically synthesized optically pure tert -butyl 6-cyano-(3 R ,5 R )-dihydroxyhexanoate ((3 R ,5 R )- 2 , > 99.5 % de p ). Under the optimized conditions, 10 mM NADP + was converted to NADPH by 5.0 mg Fe 3 O 4 @HMWCNTs, in a yield of > 80.0 %. The combination of Fe 3 O 4 @HMWCNTs with Km AKR M7 completely reduced 10 mM tert -butyl 6-cyano-(5 R )-hydroxy-3-oxohexanoate ((5 R )- 1 ) to (3 R ,5 R )- 2 , in a conversion of > 99.0 % and de p > 99.5 % . Contrast to the previous developed biocatalytic approach with Km AKR and Es GDH, this efficient and compatible nanozyme-enzyme process required neither glucose/alcohols as co-substrate nor a glucose dehydrogenase/alcohol dehydrogenase for NADPH regeneration.