Immobilized Whole-Cell Transaminase Biocatalysts for Continuous-Flow Kinetic Resolution of Amines

Abstract

Immobilization of transaminases creates promising biocatalysts for production of chiral amines in batch or continuous-flow mode reactions. E. coli cells containing overexpressed transaminases of various selectivities and hollow silica microspheres as supporting agent were immobilized by an improved sol-gel process to produce immobilized transaminase biocatalysts with suitable stability and mechanical properties for continuous-flow applications. The immobilized cell-based transaminase biocatalyst proved to be durable and easy-to-use in kinetic resolution of four racemic amines 1a–d. The batch and continuous-flow mode kinetic resolutions with transaminase biocatalyst of opposite stereopreference provided access to both enantiomers of the corresponding amines. By using the most suitable immobilized transaminase biocatalysts, this study describes the first transaminase-based approach for the production of both pure enantiomers of 1-(3,4-dimethoxyphenyl)ethan-1-amine 1d.

Transaminase-mediated synthesis of enantiopure drug-like 1-(3′,4′-disubstituted phenyl)propan-2-amines

“…Our aim was to rst optimise the asymmetric biocatalysis providing (R)-1-phenylpropan-2-amine (8a) from prochiral 1phenylpropan-2-one (7a) with the aid of our sol-gel immobilised whole-cell TA biocatalysts. 46,47 Additional goal was to extend the transamination with (R)-selective TAs to three further disubstituted derivatives (7b-d) as well (Scheme 3). Finally, to gain access to the (S)-enantiomers of the four amines by the (R)selective TAs, we also investigated the kinetic resolution of all the racemic amines.…”

“…Due to thermodynamic equilibrium reasons in the TA-mediated processes, kinetic resolution (KR) of racemic amines is more preferred to perform than asymmetric synthesis, however, at maximum conversion of the racemic substrate only 50% yield of the unconsumed enantiomer that can be achieved. 62 Because in our preliminary screens none of the (S)-selective TAs in our hands (ArS-TA, VfS-TA, CvS-TA m ) 47 showed sufficient activity in the asymmetric synthesis of (S)-8a-d, these (S)-amines were accessed by the (R)-selective TAs also, using KR of the corresponding racemic amines 8a-d (Scheme 3, Fig. 6).…”

Kinetic Resolution of Racemic Amines to Enantiopure (S)-amines by a Biocatalytic Cascade Employing Amine Dehydrogenase and Alanine Dehydrogenase

“…However, cell free extracts are unstable. Thus, whole cells expressing the enzyme of interest for the biosynthetic applications are advantageous [47]. Besides the cost effective and simpler handling of whole-cell biotransformations, an added advantage includes the utility of the enzyme production machinery of the fully functional living organism [48,49].…”

Use of Immobilized Amine Transaminase from Vibrio fluvialis under Flow Conditions for the Synthesis of (S)‐1‐(5‐Fluoropyrimidin‐2‐yl)‐ethanamine

“…Both biocatalysis and continuous processing do have the features that make these technologies as the foremost key green research areas for sustainable manufacturing of APIs and fine chemicals. Biocatalysts, either enzymes or whole cells, are typically immobilized onto the reactor wall or on particles of a carrier material, which is then packed into a column to form a packed‐bed reactor with a plug‐flow behavior . Among the various methods for enzyme immobilization, covalent immobilization is probably the most successful approach, allowing a robust attachment of the enzyme.…”