In recent years, enzyme promiscuity in organic synthesis has drawn immense attention due to its intrinsic advantages such as environment-benign, good selectivity, simple separation and mild reaction conditions. The study of enzyme catalyst not only provided a new, green and highly effective reaction pathway, but also enriched theoretical enzymology and expanded the scope of enzyme catalysis. This dissertation focuses on hen egg white lysozyme-catalyzed aza-Diels-Alder reaction and papain-catalyzed Knoevenagel reaction.Aza-Diels-Alder reaction was one of the most powerful tools to construct nitrogen-containing bioactive heterocycles. In this dissertation, the direct three-component aza-Diels-Alder reaction of aromatic aldehyde, aromatic amine and2-cyclohexen-1-one was first catalyzed by enzyme, and various reaction parameters involving solvents, the mole ratio of substrates, water contents, temperature, enzyme concentration were investigated. Moreover, in order to further confirm that the specific catalytic effect of the enzyme, we performed some control experiments involving blank reaction and denatured enzyme catalyzed reaction. The results indicated that the native active site was responsible for its activity in aza-Diels-Alder reaction. Ten kinds of aromatic aldehydes and two types of aromatic amine were used to expand upon the enzyme-catalyzed aza-Diels-Alder reaction at the optimized conditions which gave yields up to98%and stereoselectivity of endo/exo ratios up to90:10. Furthermore, a possible mechanism was proposed for the enzyme-catalyzed aza-Diels-Alder reaction in the dissertation.Knoevenagel reaction is one of the most useful methods for carbon-carbon bond formation. It has been widely applied in the preparation of pharmaccuticals and fine chemicals. In this dissertation, we reported the papain-catalyzed Knoevenagel reaction for the first time. The effects of solvents, water contents, temperature and papain loadings were investigated. Under the optimized conditions, papain can catalyze Knoevenagel condensation with a wide range of aromatic, hetero-aromatic and a,p-unsaturated aldehyde and1,3-diketones resulting in moderate to good yields. Based on these results, we hypothesized the mechanism of papain-catalyzed Knoevenagel reaction.Our research not only widens the application of hen egg white lysozyme and papain to chemical transformation, but also could be developed into a potentially valuable method for organic synthesis. |