No Solvent System Enzymatic Resolution Of ¦Á-phenylethanol

The importance of chiral technology and the progress on the preparation of optical pure chemical compounds were reviewed <, The production of optical pure chemicals by chiral resolution catalyzed by enzymes or microorganisms was highly recommended <>In this paper it was concentrated on the chiral resolution of racemic a -phenyl ethanol(l- phenyl ethanol) by lipase. The optimization of the reaction conditions was also conducted. At last kinetic modeling of lipase-catalyzed transesterification of α -phenyl ethanol was set up.α -Phenyl ethanol was one of the important chiral building blocks for organic synthesis. Vinyl acetate was used as both the acyl donor and the solvent. And lipase was used as catalyst.a -Phenyl ethanol was transesterified with vinyl acetate, The product α-phenylethyl acetate was approximately 100% enantiomeric pure.The concentrations of different enantiomer of substrate and product were analyzed by gas chromatography with chiral column respectively, from which the enantiomeric excess of substrate and product was calculated. The operation conditions were: carrier gas: N2 20ml/min, hydrogen 45ml/min, air 400ml/min, column temperature 85℃, inlet temperature 250℃, detector(FID) 250℃.35 kinds of lipase were screened. 10 kinds of lipase with higher reaction activity and enantioselectivity were selected and rescreened. Finally Novozyme 435 was chosen as the best enzyme to be optimized with the reaction conditions.The catalytic behaviors of lipase Novozyme 435 were investigated, including the influence of temperature, rotation speed, the concentration of substrate and the amount of the enzyme. It was found that the optimal temperature and rotation speed were at 40℃ and 150 rpm respectively. And in 2 ml reaction volume 20 mg enzyme was enough. The suitable total concentration of phenyl ethanol was 600mmol/L. At the optimized reaction conditions, when the reaction time was about 630 min, theconversion rate of R-α -phenyl ethanol reached 98.9%, in the meanwhile the e.e. of S-phenyl ethanol and R- a - phenylethyl acetate were 97.8% and 99.4% respectively.The effect of reusing enzyme was studied, when reaction time reached 550min, the conversion of R- a -phenyl ethanol was 97.3%, 72.5%and 65.7% when enzyme was first , second and third used, the e.e. of S-1-phenyl ethanol dropped about 46%, but the e.e. of R-l-phenylethyl acetate remained unvaried.Because S-enantiomer of a -phenyl ethanol did not react with vinyl acetate, the kinetics of R- a -phenyl ethanol was studied only, the reaction mechanism was hypothesized to be a ping-pong bi-bi reaction as a whole, the rate equation was:The five parameters of this equation were simufited and calculated. Vm=0.0105mM/min, KA=0.495mM, KB=0.00019, KQA=0.0041 KBQA=0.000015 Thus the rate equation becameThe equation with the parameters substituted was used to expect the conversion at different concentrations of substrate, and got satisfying results. Finally some suggestions were proposed for further study.