Biocatalytic Cascade Synthesis of Enantioenriched Epoxides and Triols from Biomass‐Derived Synthons Driven by Specifically Designed Enzymes

Multi‐enzymatic cascades exploiting engineered enzymes are a powerful tool for the tailor‐made synthesis of complex molecules from simple inexpensive building blocks. In this work, we engineered the promiscuous enzyme 4‐oxalocrotonate tautomerase (4‐OT) into an effective aldolase with 160‐fold increased activity compared to 4‐OT wild type. Subsequently, we applied the evolved 4‐OT variant to perform an aldol condensation, followed by an epoxidation reaction catalyzed by a previously engineered 4‐OT mutant, in a one‐pot two‐step cascade for the synthesis of enantioenriched epoxides (up to 98 % ee) from biomass‐derived starting materials. For three chosen substrates, the reaction was performed at milligram scale with product yields up to 68 % and remarkably high enantioselectivity. Furthermore, we developed a three‐step enzymatic cascade involving an epoxide hydrolase for the production of chiral aromatic 1,2,3‐prim,sec,sec‐triols with high enantiopurity and good isolated yields. The reported one‐pot, three‐step cascade, with no intermediate isolation and being completely cofactor‐less, provides an attractive route for the synthesis of chiral aromatic triols from biomass‐based synthons. Here, we report the design and application of multi‐step enzymatic cascades to synthesize enantioenriched epoxides and vicinal aromatic triols from simple biomass‐derived starting materials in one pot. These artificial metabolic pathways involve a tailor‐made aldolase, a highly evolved cofactor‐independent peroxyzyme, and when needed a specifically chosen epoxide hydrolase. These attractive biocatalytic cascades can be performed under environmentally benign conditions, such as the use of aqueous media and mild temperatures, and do not require the isolation of reaction intermediates. Good to excellent conversions, high enantioselectivity, and moderate to good product yields are achieved.