ω-Transaminase-Mediated Asymmetric Synthesis of (S)-1-(4-Trifluoromethylphenyl)Ethylamine

Carlos J C Rodrigues,Manuel Ferrer,Carla C C R De Carvalho

doi:10.3390/catal11030307

Abstract

The pivotal role played by ω-transaminases (ω-TAs) in the synthesis of chiral amines used as building blocks for drugs and pharmaceuticals is widely recognized. However, chiral bulky amines are challenging to produce. Herein, a ω-TA (TR8) from a marine bacterium was used to synthesize a fluorine chiral amine from a bulky ketone. An analysis of the reaction conditions for process development showed that isopropylamine concentrations above 75 mM had an inhibitory effect on the enzyme. Five different organic solvents were investigated as co-solvents for the ketone (the amine acceptor), among which 25–30% (v/v) dimethyl sulfoxide (DMSO) produced the highest enzyme activity. The reaction reached equilibrium after 18 h at 30% of conversion. An in situ product removal (ISPR) approach using an aqueous organic two-phase system was tested to mitigate product inhibition. However, the enzyme activity initially decreased because the ketone substrate preferentially partitioned into the organic phase, n-hexadecane. Consequently, DMSO was added to the system to increase substrate mass transfer without affecting the ability of the organic phase to prevent inhibition of the enzyme activity by the product. Thus, the enzyme reaction was maintained, and the product amount was increased for a 62 h reaction time. The investigated ω-TA can be used in the bioconversion of bulky ketones to chiral amines for future bioprocess applications.

Highlights

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Novel biocatalysts are being increasingly developed for different industrial applications [5,6,7,8], and novel enzymes have been successfully bioprospected from rarely explored habitats [9,10,11,12]
The experiments showed that the initial bioconversion rate of cell extract containing TR8 varied linearly until a maximum concentration of 1.5 g L−1 (Figure S1)

Summary

Introduction

Biocatalysts are being explored as green alternatives to alleviate environmental problems created by the use of traditional organic chemistry [1,2]. Biocatalysts, either in the form of whole cells or isolated enzymes, catalyze the transformation of chemical substrates to target product molecules. Biocatalysts operate under mild conditions and in aqueous environments, usually require fewer reaction steps than traditional chemistry, and are renewable [3,4]. The application of biocatalysts to bioprocesses is associated with economic and environmental benefits. Novel biocatalysts are being increasingly developed for different industrial applications [5,6,7,8], and novel enzymes have been successfully bioprospected from rarely explored habitats [9,10,11,12]. Transaminases have been found to deliver novel and enantiomeric pure molecules as building blocks for the pharmaceutical industry [13,14,15,16]

Methods

Results

Conclusion