Efficient Biocatalytic Preparation of Optically Pure (<i>R</i>)-1-[4-(Trifluoromethyl)phenyl]ethanol by Recombinant Whole-Cell-Mediated Reduction

• Main Authors: Ying Chen, Nana Xia, Yuewang Liu, Pu Wang
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: Catalysts
• Subjects: (<i>R</i>)-1-[4-(trifluoromethyl)phenyl]ethanol; asymmetric bioreduction; recombinant whole-cell catalysis; polar organic solvent-aqueous system
• Online Access: https://www.mdpi.com/2073-4344/9/4/391

(<i>R</i>)-1-[4-(Trifluoromethyl)phenyl]ethanol is an important pharmaceutical intermediate of a chemokine CCR5 antagonist. In the present study, a bioprocess for the asymmetric reduction of 4-(trifluoromethyl)acetophenone to (<i>R</i>)-1-[4-(trifluoromethyl)phenyl]ethanol was developed by recombinant <i>Escherichia coli</i> cells with excellent enantioselectivity. In order to overcome the conversion limitation performed in the conventional buffer medium resulting from poor solubility of non-natural substrate, we subsequently established a polar organic solvent-aqueous medium to improve the efficacy. Isopropanol was selected as the most suitable cosolvent candidate, based on the investigation on a substrate solubility test and cell membrane permeability assay in different organic solvent-buffer media. Under the optimum conditions, the preparative-scale asymmetric reduction generated a 99.1% yield with &gt;99.9% product enantiomeric excess (ee) in a 15% (<i>v</i>/<i>v</i>) isopropanol proportion, at 100 mM of 4-(trifluoromethyl)acetophenone within 3 h. Compared to bioconversion in the buffer medium, the developed isopropanol-aqueous system enhanced the substrate concentration by 2-fold with a remarkably improved yield (from 62.5% to 99.1%), and shortened the reaction time by 21 h. Our study gave the first example for a highly enantioselective production of (<i>R</i>)-1-[4-(trifluoromethyl)phenyl]ethanol by a biological method, and the bioreduction of 4-(trifluoromethyl)acetophenone in a polar organic solvent-aqueous system was more efficient than that in the buffer solution only. This process is also scalable and has potential in application.