Production of High Value Amine Intermediates via Biocatalytic Cascades in Continuous Flow

Abstract

<div> <p>A key aim of biocatalysis is to mimic the ability of eukaryotic cells to carry out compartmentalized multistep cascades in a controlled and selective way. As biocatalytic cascades get longer and more complex, reactions become unattainable under typical batch conditions. Here a continuous flow multipoint injection reactor was combined with switching valves to overcome batch incompatibility, thus allowing for successful biocatalytic reaction cascades. As proof-of-principle, several reactive carbonyl intermediates were generated <i>in situ </i>using galactose oxidase and engineered choline oxidases, then passed directly to a series of packed-bed modules containing different aminating biocatalysts which accordingly produced a range of structurally distinct amines. The method was expanded to employ a batch incompatible sequential amination cascade <i>via </i>an oxidase-transaminase-imine reductase sequence, introducing different amine reagents at each step without cross reactivity. The combined approaches allowed for the biocatalytic synthesis of the natural product alkaloid precursor 4O-methylnorbelladine. The flow biocatalysis platform shown here significantly increases the scope of novel biocatalytic cascades, removing previous limitations due to reaction and reagent batch incompatibility.</p> </div> <b><br></b>

Streamlining Design, Engineering, and Applications of Enzymes for Sustainable Biocatalysis

“…191 Compartmentalization of reactions permitted by flow chemistry enables reactions that would otherwise be unfeasible. In a striking example, Mattey et al 192 demonstrated the synthesis of primary and secondary amines using flow chemistryincluding 4′-O-methylnorbelladine, a precursor for pharmacologically active alkaloid scaffolds such as the dementia drug galantamine. It involves the use of a galactose oxidase (GO) to convert alcohols to the starting aldehydes, and then either a transaminase to generate primary amines, or a reductive aminase (ReAm/IRED) (combined with a NADPH regenerating GDH) for secondary amines.…”