Asymmetric Synthesis of (R)-3-fluoroalanine from 3-fluoropyruvate Using Omega-transaminase

In this study, (R)-3-fluoroalanine was asymmetrically synthesized from 3-fluoropyruvate (F-pyruvate) and (S)-alpha-methylbenzylamine (MBA) using recombinant omega-transaminase (TA) from Vibrio fluvialis JS17. The reaction was severely inhibited by acetophenone (deaminated product of alpha-MBA). In the presence of 5 mM acetophenone, the reactivity of the enzyme towards F-pyruvate decreased by 78%. To overcome the product inhibition by acetophenone, a biphasic reaction was successfully used. The conversion of F-pyruvate into (R)-3-fluoroalanine (enatiomeric exess (e.e.) > 99%) was about 95% in the biphasic system (75 mM F-pyruvate, 100 mM (S)-alpha-MBA, and 3.0 U/mL), whereas 31% was obtained without product extraction. The use of racemic alpha-MBA as an amino donor instead of (S)-alpha-MBA can reduce the reaction cost and also produce chiral amines through kinetic resolution. When the kinetic resolution of racemic alpha-MBA (40 mM) was carried out with F-pyruvate (30 mM) and omega-TA (3.0 U/mL) in 100 mM phosphate buffer (pH 7.0), the e.e. of (R)-alpha-MBA reached 98.4% with 52.2% conversion for 10 h and 21 mM (R)-3-fluoroalanine was produced with 70% conversion and an e.e. > 99%.