Research On Preparation Of Chiral α-bromo-γ-butyrolactone With Biological Methods

Substituted y-butyrolactone are widely used in pharmaceutical and pesticide industry.Most of the lactone compounds have one and more chiral centers,and their physiological activities generally depend on the absolute configurations of the molecules.In this thesis,the strains with lactonase were isolated from rich oil soil samples and hydrolase producting strains preserved by our laboratory to resolve the a-bromo-y-butyrolactone which was the subject of the study.A strain with relatively good hydrolytic ability was sctreened,and was named as R.mucilaginosa ZQ012.Then the fermentational medium composition,culture conditions and transformation conditions were optimized.In addition,different commercial lipases used to catalyze the selective transesterification reaction of a-bromo-y-butyrolactone were investigated.Based on single factor experiments,the optimized fermentational medium composition and culture conditions for R.mucilaginosa ZQ012 were as follows:maltose 1%,peptone 1%,NaCl 1%,KH2PO4 0.1%,K2HPO4-3H2O 0.3%,MgSO4 5mM/L,intial fermentation pH 7.5,constant temperature shaker speed 200rmp,culutre temperature 30℃,cultivated for 48h.Under these optimal conditions,the e.e.s value of the substrate increased from the initial 33.4%to 57.0%,nearly doubled.Meanwhile,the conversion rate of the substrate was 58.6%,and the E value was 4.0.Conditions for kinetic resolution of a-bromo-y-butyrolactone by R.mucilaginosa ZQ012 lactonase were also studied.The optimized resolution conditions were as follows:1OmL reaction system,cyclohexane 25%(Ⅴ/Ⅴ),ethyl acetate 25%(Ⅴ/Ⅴ),0.1M pH8,0 phosphate buffer 50%(V/V),a-bromo-γ-butyrolactone 1%(V/V).The reaction mixture was shaken(200 rpm)in a water shaking bath at 30 ℃for 6 hours.The e.e value of the substrate increased from the initial 58.6%to 84.4%,and the conversion rate vaule of the substrate 58.6%,the E value of the substrate 15.5,were obtained.Finally,different commercial lipases used to catalyze the selective transesterification reaction of a-bromo-y-butyrolactone were investigated.Using(lipase from Thermomyces lanuginous)TLIM.as Biocatalysts,isooctane as solvent,the optimized selective transesterification conditions for the reaction of a-bromo-γ-butyrolactone and n-propanol were as follows:substrate concentration 0.5%,water activity 2μL/mL,temperature 30℃.Then the reaction mixture was shaken(200 rpm)in a water shaking bath at 30℃ for 36 hours.The e.e value of the substrate 29.3%,the conversion rate vaule of the substrate 51.1%,the E value of the substrate 1.0,were obtained.