Preparation method of ethyl (R)-4-cyano-3-hydroxybutyrate

The invention discloses a preparation method of ethyl (R)-4-cyano-3-hydroxybutyrate. According to the preparation method, ethyl (S)-4-chloro-3-hydroxybutyrate is taken as a substrate, immobilized halohydrin dehalogenase is taken as a catalyst, the substrate and the catalyst react with cyanide salt under the condition of pH value in a range from 6.5 to 8.0, and ethyl (R)-4-chloro-3-hydroxybutyrate is obtained; a preparation method of immobilized halohydrin dehalogenase comprises steps as follows: adsorbent resin is added to a halohydrin dehalogenase solution, the halohydrin dehalogenase is adsorbed on the adsorbent resin and crosslinked by a difunctional crosslinking agent, finally, the adsorbent resin is separated from the halohydrin dehalogenase solution and washed, and the immobilized halohydrin dehalogenase is obtained. The enzyme recovery rate of the immobilized halohydrin dehalogenase is high, the operation stability is high, reduction of production cost is facilitated, when the immobilized halohydrin dehalogenase is used for preparing ethyl (R)-4-cyano-3-hydroxybutyrate, the process is simple, the resolution effect is excellent, e.e. value can be up to 99%, particularly, the postprocessing is simpler, and the yield can be higher than 91%.