Asymmetric Bioreduction of 3,5-Bis(trifluoromethyl) Acetophenone to Its Corresponding Alcohol by Candida tropicalis

(S)-3,5-bistrifluoromethylphenyl ethanol is a key chiral intermediate for the synthesis of NK-1 receptor antagonists. Enantioselective synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol was successfully performed in high enantiomeric excess (e.e.) through asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone catalyzed by Candida tropicalis 104 cells. The influence of some key reaction parameters such as substrate concentration, co-substrate and its concentration, biomass and reaction time was examined, respectively. The results showed that these factors obviously influence the yield, but the optical purity of the prepared product remains intact. The optimum conditions for the preparation of (S)-3,5-bistrifluoromethylphenyl ethanol were found to be as follows: substrate concentration 50 mmol·L−1; 50 g·L−1 of maltose as co-substrate; wet cell concentration 300 g·L−1; reaction for 30 h. Under above optimal conditions, the maximum yield for (S)-3,5-bistrifluoromethylphenyl ethanol reached 70.3% with 100% of product e.e.