Development of an in situ‐Product Crystallization (ISPC)‐Concept to Shift the Reaction Equilibria of Selected Amine Transaminase‐Catalyzed Reactions

Abstract

The synthesis of enantiopure amines via amine transaminases involves several challenges including unfavorable reaction equilibria and product inhibition. Described here is a non‐catalytic approach to overcome such problems by using an in situ‐product crystallization (ISPC) to selectively remove a targeted product amine from an amine transaminase‐catalyzed reaction. The continuous removal of the product amine from its reaction solution as a barely soluble salt effectively yields a displacement of the reaction equilibrium towards the products and facilitates a simple downstream processing approach via filtration. The targeted product amine is eventually obtained from the salt, while the counterion compound can be easily recycled.

Donor Amine Salt‐Based Continuous in situ‐Product Crystallization in Amine Transaminase‐Catalyzed Reactions

“…Enantiomeric excesses of the obtained amines were measured by High Performance Liquid Chromatography (HPLC) as described earlier. [12]…”

“…As an alternative we've recently introduced the use of in situ-product crystallization (ISPC) of the product salt to shift the transaminase reaction equilibrium. [12,13] The apparent equilibrium shift is obtained by salt formation of the product with a specifically chosen counter-ion, which eventually crystallizes from solution. Product salt isolation is then easily achieved by a simple filtration step.…”

One‐pot Synthesis of 4‐Aminocyclohexanol Isomers by Combining a Keto Reductase and an Amine Transaminase

“…Solid-phase extraction with Oasis WCX (weak cation exchanger) or Sep-Pak® tC18 Silica columns was not working because 1 started to elute from the columns already during the washing step. The precipitation of 1 with organic acids, such as 3,3-diphenylpropionic acid was also possible, [26] but required more optimization steps due to high solubility of the salt. Thus, the best isolation approach was an optimized extraction protocol and crystallization as hydrochloride (see SI), facilitating � 75 % isolated yield in most cases.…”

Application of In Situ Product Crystallization and Related Techniques in Biocatalytic Processes

“…As imilar,b ut slightly more complex, ISPC concept was recently described by Hülsewede et al for selected amine transaminase catalyzed reactions (Scheme 5). [41] Herein, transaminase-catalyzed reactions exhibit, in comparison to decarboxylases, as imilarly poor reactione quilibrium towards the synthesis of chiral product amines 15 from the corresponding prochiral ketones 12.C lassically,t his is solved by an excessive overstoichiometrica mount of the cosubstrate isopropylamine (13), other tailor-made donor amines, or complex( bio)catalytic Scheme2.Isomerization and ISPC of selectedt hreonine isomers.…”