The Enzyme-catalyzed Direct Asymmetric Aldol Reaction And Biginelli Reaction

Enzymes have been given special attention and developed rapidly in organic synthesis due to its intrinsic advantages such as mild reaction conditions, simple separation and environment-benign. The exploration and study of enzyme catalyst cannot only widen the range of applications of existing enzymes, but also provide a green, efficient synthetic method for organic chemistry, which is a challenging and attractive research topic. In this thesis, we reported trypsin from porcine pancreas, CYL-enzyme A, CYL-enzyme B catalyzed aldol reaction and CYL-enzyme B catalyzed Biginelli reaction in organic solvents.Trypsin from porcine pancreas is a serine protease whose active site amino acid is serine, and we first reported trypsin from porcine pancreas catalyzed direct asymmetric aldol reaction. Through the screening of the solvents, the mole ratio of substrates, water contents, temperature, enzyme concentrations and other conditions, we established the optimum reaction conditions for the trypsin-catalyzed aldol reaction. Subsquently, we studied the generality of the trypain-catalyzed direct asymmetric aldol reaction, and found that the different types and positions of the substituents in the benzene ring of aromatic aldehydes have important influence on the catalytic activity and stereoselectivity of the enzyme. The best yield of60%was obtained from nitrobenzaldehyde and65%ee value was observed by trifluoromethylbenzaldehyde. Meanwhile, we purified the trypsin and performed some control experiments. The results indicated that the trypsin-catalyzed aldol reaction took place in the native active site. Based on these results, we hypothesized the mechanism of trypsin-catalyzed aldol reaction.CYL-enzyme A is an important hydrolase and we first found that it had excellent ability to catalyze asymmetric aldol reaction with the yield up to99%and>99%ee. In order to verify that CYL-enzyme A could be recovered and reused, we performed a recycling study of CYL-enzyme A. And decrease of the catalytic ability of the CYL-enzyme A was observed after three cycles. The aldol reaction between cyclohexanone and isatin was explored, which was obtained37%ee value with excellent yield up to99%. In addition, the recrystallization experiment was performed for several products and good yields with excellent ee values were obtained.CYL-enzyme B is a complex enzyme with high catalytic ability to aldol reaction, which was developed independently by our group. We established the optimum reaction conditions for the enzyme-catalyzed aldol reaction by screening the solvents, the mole ratio of substrates, water contents, temperature, enzyme concentrations and other conditions. Up to28kinds of substrates were employed to the enzyme-catalyzed aldol reaction and provided the yields up to95%and up to98%ee. Meanwhile, this enzyme also has catalytic ability to heterocyclic ketones with aldehydes. The yield of the4-piperidinone was achieved up to94%. In addition, we also carried out a blank test and a series of control experiments to confirm the role of CYL-enzyme B on this reaction. This method offered the possibility for the enzyme-catalyzed direct asymmetric reactions in industrial production.Biginelli reaction is one of the most important multi-component reactions, which provides an efficient synthetic route to3,4-dihydropyrimidin-2(1H)-ones (DHPMs) compound. The catalysts for this reaction mainly included HCl, ZnCl2and [bmim][FeCl4], and they not only are toxic, but also have other shortcomings such as environmental pollution, harsh reaction conditions and so on. Hence, it is significant to find an efficient and sustainable catalyst for this reaction. So far, only Zhang’s group reported the enzyme-catalyzed Biginelli reaction with high yield but without stereoselectivity. We found that CYL-enzyme B could catalyze Biginelli reaction, and we also established the optimum reaction conditions by screening the solvents, the mole ratio of substrates, water contents, temperature, enzyme concentration and other conditions. The results demonstrated that CYL-enzyme B had good catalytic activity and enantioselectivity to Biginelli reaction, which not only provided69%yield, but also achived the ee value up to56%for the first time. Moreover, this enzyme also had wide substrate scope.