Enzyme Catalyzed Three-component Reaction,Michael Reaction And Asymmetric Michael Reaction:Efficient Construction Of Oxindoles,Spirooxindole And Coumarin Anticoagulant

The development of enzyme catalytic promiscuity in nonaqueous media has been investigated in the last two decades. The results of study have changed the traditional understanding of enzymes; that enzymes would be inactive in organic solvents. Enzyme catalytic promiscuity means that not only natural substrates but also non-natural substrates can be catalyzed by the active site of an enzyme in natural or unnatural conditions. Enzyme catalytic promiscuity can be investgated for the development of green catalysts for organic synthesis and can further our understanding of enzyme evolution. Many enzymes have been reported to be excellent catalysts for aldol, Henry and Knoevenagel reactions; but multicomponent or casecade reactions and asymmetric Michael reactions catalyzed by enzymes are seldom reported.The oxindoles are the core structural motif which are present in many natural products and biologically active compounds. A large number of compounds containing these structural units show pharmaceutical and biological activity.3,3’-Disubstituted oxindoles and spirooxindoles containing a quaternary carbon center and diverse functional groups are powerful synthetic intermediates which provide a shortcut to synthesize complex and potentially biologically active compounds. Because of these promising advantages, more and more chemists are trying to develop greener and easier methods to synthesize 3,3’-disubstituted oxindole and spirooxindole frameworks. Herein we report the synthesis of oxindole and spirooxindole frameworks catalyzed by a-amylase via a one-pot three-component reaction. We have optimized the reaction conditions of solvents, water content, temperature, and catalyst loading, with 98% yield in the best conditions. Based on the control reaction, we confirmed that the natural activity of a-amylase is responsible for the three-component reaction and have speculated on the mechanism of the three-component reaction. Our work has expanded the application of a-amylase in organic chemistry. Besides the a-amylase, we found pepsin is also an excellent catalyst for cascade reactions. After optimizing reaction conditions, the reaction could be finished in 12 hours in 95% yield and 99:1 dr. Substrate scope showed that all kinds of α,β-unsaturated ketones can participate in cascade reactions. Pepsin also showed good catalytic ability for aromatic heterocycte and aliphatic α,β-unsaturated ketones affording excellent dr values.Warfarin, a coumarin derivative, is one of the most widely used and of the best anticoagulant medications and has been used as an oral anticoagulant drug in treatment and prevention of thromboembolic disorders for more than half a century. Even though there is a chiral center in Warfarin, it is continually administered as a racemic mixture. According to recent reports, the anticoagulant activity of S-Warfarin is 2-5 times higher than R-Warfarin, which emphasizes the importance of synthesizing pure S-Warfarin. Although several efficient methods have been achieved, few reports about asymmetric Michael reactions between coumarin and benzalacetone are catalyzed by enzymes. The best yields (up to 99%) and best ee (up to 39%) can be achieved in optimal reaction conditions. This method for constructing Warfarin catalyzed by pepsin has expanded the application of pepsin in organic chemistry.