Chiral vicinal amino alcohols are an important motif found in many biologically active molecules. In this study, biocatalytic reductive amination of α-hydroxy ketones with ammonia was investigated using engineered amine dehydrogenases (AmDHs) derived from the leucine amino acid dehydrogenase (AADH) from Lysinibacillus fusiformis. The AmDHs thus identified enabled the synthesis of (S)-configured vicinal amino alcohols from the corresponding α-hydroxy ketones in up to 99% conversions and >99% ee. One of the AmDH variants was used to prepare a key intermediate for the antituberculosis pharmaceutical ethambutol.

A key aim of biocatalysis is to mimic the ability of eukaryotic cells to carry out multistep cascades in a controlled and selective way. As biocatalytic cascades get more complex, reactions become unattainable under typical batch conditions. Here a number of continuous flow systems were used to overcome batch incompatibility, thus allowing for successful biocatalytic cascades. As proof‐of‐principle, reactive carbonyl intermediates were generated in situ using alcohol 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 via 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 4O‐methylnorbelladine.

The NADP(H)‐dependent reductive aminase from Aspergillus oryzae (AspRedAm) was combined with an NADPH oxidase (NOX) to develop a redox system that recycles the co‐factor. The AspRedAm‐NOX system was applied initially for the kinetic resolution of a variety of racemic secondary and primary amines to yield S‐configured amines with enantiomeric excess (ee) values up to 99 %. The addition of ammonia borane to this system enabled the efficient deracemization of racemic amines, including the pharmaceutical drug rasagiline and the natural product salsolidine, with conversions up to >98 % and >99 % ee Furthermore, by using the AspRedAm W210A variant it was possible to generate the opposite R enantiomers with efficiency comparable to, or even better than, the wildtype AspRedAm.

Monoacylated diamines are common motifs present in pharmaceuticals, agrochemicals, and natural products. However, the synthesis of these compounds often requires selective protection/deprotection steps leading to waste and poor atom economy. Here we describe the truncation of a carboxylic acid reductase (CAR) yielding an adenylation domain capable of selective amide bond formation under aqueous conditions. This truncated construct had a higher amidation activity compared to the full-length enzyme. The amidation reaction is mediated by ATP, which can be recycled from polyphosphate using a class III polyphosphate kinase (CHU). The wide substrate scope and selectivity of this enzymatic amidation method were confirmed through the synthesis of 24 pharmaceutically relevant amides including building blocks of six active pharmaceutical ingredients (APIs). Moreover, up-scaling of selected examples, including two API’s, was achieved demonstrating the value of this approach for synthesis.

A mild, biocatalytic alternative to the conventional amination of fatty acids through a one-pot tandem cascade performed by a carboxylic acid reductase (CAR) and a transaminase (ω-TA).