Study On Preparation Of R-Lipoic Acid From Rac-Lipoic Acid By Enzyme Resolution

α-Lipoic acid is an antioxidant containing sulphur.Sinceα-Lipoic acid exhibits a high level of biological activity,its use in the treatment of various diseases has been investigated.For example,it shows effects in diabetes mellitus and hepatic disease as well as anti-oxidative,anti-inflammatory and immunological activity.Generally,the （R）-enantiomer is much more active than the（S） -enantiomer.Therefore,great attention has been focoused on the stereoselective synthesis of pure（R） -enantiomer. Chemical methods is the main routes for the synthesis of（R） -enantiomer,and various methods of enzyme catalysis have also been developed.In this study,one method of preparation of（R） -lipoic acid by enzyme resolution has been built.In this study,Aspergillus oryzae WZ007 has been screened.Its enzyme can enantioselectively esterify（S） -lipoic acid to the corresponding（S） -ester,and that the residual（R） -lipoic acid can be recovered by extraction with high excess data.The condition for enzyme production of Bacillus thuringiensis M2 was studied. The appropriate culture medium ingredients were:sucrose 1.25%,peptone 0.5%, K₂HPO₄ 0.12%,MgSO₄ 0.1%,NaCl 0.05%,olive oil 0.25%,initial pH 5.2。The optimized condition for enzyme production is temperature 30℃,rotate speed 2000rpm.The enzymatic activity was 2.67U/L in optimized condition.The esterification condition was also optimized.An optimal reacting condition:1 mmol rac-lipoic acid,5:1 molar ratio of n-octanol to rac-Lipoic acid and 200 mg freezingdried powder of WZ007 in 20ml Heptane,reacting temperature 50℃,shaking at 20 rpm.In this optimal reacting condition,the conversion and ee_s were 75.2%and 92.5%respectively.