Chloroperoxidase Catalyzed Oxidation Directional Synthesis Of Chiral Modafinil

Chloroperoxidase (CPO) has various catalytic activities and broad substrate acceptance due to its unique active site structure. The most interest characteristic of the CPO is the chiral catalytic activity, such as enantioselective sulfoxidation, which are applied in chiral medicine and preparation of medical intermediate. So it's a biocatalyst with potential applications for industry.Chiral modafinil synthesis by chiral metallo catalysts having some disadvantage such as synthesizing the catalysts was extremely difficult and the enantioselectivity is low. In this work, TBHP/H2O2was chosen as the O2donor, catalyzed by chloroperoxidase (CPO) oriented synthesis of R-modafinil, we investigated the influence of several reaction conditions, and the yield of expected products was enhanced by solvent engineering based on co-solvent effect of organic solvents and the additive effect of hydrophilic imidazole ionic liquids ([EMIM][Br],[PMIM][Br],[BMIM][Br],[AMIM][Br]), hydrophilic quaternary ammonium salt (TMABr, TEABr, TPABr, TBABr), polyhydroxy compounds(glycerol, PEG400, PEG600) and organic solvent(CH3CH2OH, CH3CN, CH3COCH3, THF, DMF, DMSO). Those additives improve the stability of CPO and the convert ratio of hydrophobic substrates. we had discussed the enhance mechanism of CPO on the molecular level by the spectroscopy. in this section, we used glucose oxidase(GOD) and glueose generating H2O2to the controlled release of H2O2, to avoid high concentration of H2O2inhibitory the activity of CPO. By comparing two methods about externally supplied and enzymatically produced of H2O2to investigate the effect of product yield. The major results are as follows:1. Asymmetric sulfoxidation of2-benzhydrylsulfanyl acetamide catalyzed by CPO to oriented synthesis of R-modafinil was influence of several reaction conditions, including the kind of additive, pH effect, choice of oxidants, CPO consumption and the reaction time. The most efficient additive was1-Ethyl-3-methylimidazolium bromide [EMIM][Br], when chose TBHP as the O2donor, the concentration of TBHP:substrate=1.5:1, pH5.5, the yield and enantioselectivity of (R)-modafinil reach to40.8%and96.7%. The decrease of enzyme kinetic parameters Km and increase of Kcat and Kcat/Km indicated that both the affinity and specificity of CPO to the substrate were improved in the presence of QAS, resulting in the increase of turnover number. Moreover, UV-vis and circular dichroism assay and analysis of products composition indicated that the additives played multiple functions in this enzyme-catalyzed reaction: inducing catalytically favorable conformation of CPO, phase transfer catalysis and improve the solvability of substrate.2. we used glucose oxidase(GOD) and glueose generating H2O2to avoid at lower concentration H2O2insufficient, while at higher concentration it inhibitory activity of CPO. To optimize the conditions, we studied the effect of pH, concentrations of GOD, hydrogen peroxide to get the analytical characteristic of the method. To controlled the release of H2O2, a sustainable constant activity of CPO was observed. Under Optimum Conditions, the yield of R-modafinil raises from32.4%in the single enzyme system to36.4%in the CPO-GOD coupling system.