Study On The Synthesis Of Nitrogen-Containing Heterocyclic Compounds Via Enzymatic Multicomponent Reactions

As a new tool, biocatalytic synthesis in organic chemistry has attracted lots of attention. In recent years, many enzymes have shown catalytic promiscuity, such as, acylase and protease catalyzed Michael addition, racemase catalyzed the aldol reaction, acylase and transglutaminase catalyzed Henry reaction, and hydrolase accelerated many achievements in terms of enzymatic organic synthesis. However, enzymatic one-pot multicomponent reactions are scarcely reported, especially to synthesize complicated and bioactive heterocycles.A direct method to construct3,4-dihydropyridin-2-ones by enzymatic condensation of aldehyde with cyanoacetamide and1,3-dicarbonyl compounds was developed. Four new bonds and one six-member aza-ring were formed by one-pot method. Controlled experiments involving catalyst-free, BSA and denatured AA verified the role of active site, its catalytic mechanism was further proposed. And reaction conditions involving hydrolases, solvents, substrate molar ratios, hydrolase loadings and substrate variations were optimized. A series of new compounds based on the3,4-dihydropyridin-2-one core were synthesized.The Acylase "Amano"(AA)-catalyzed synthesis of valuable pyridin-2-ones via domino Knoevenagel condensation-Michael addition-intramolecular cyclization-oxidization reaction between aldehyde, cyanoacetamide and ethyl acetoacetate or cyclohexyl acetoacetate was also developed by the one-pot strategy. Reaction conditions involving hydrolases, solvents, temperatures, catalyst loadings and substrate variations were investigated. And controlled reaction under nitrogen atmosphere illustrated that pyridin-2-one was formed via the oxidization by oxygen at the final step.An efficient approach for the synthesis of highly substituted pyridin-2-one derivatives via Acylase "Amano"(AA)-catalyzed three-component reaction between aromatic aldehyde, cyanoacetamide and ketone was proposed. Studies showed that this reaction involved five molecules, which could in situ generate hydrogen donor (3,4-dihydropyridin-2-one) and hydrogen acceptor (Knoevenagel condensation product). The internal transfer hydrogenation process was further confirmed after we quantitatively detected the transforming course of the two intermediates by HPLC; Using this method, pyridin-2-ones and a-alkylated nitriles could be obtained simultaneously, and the a-alkylated nitrile could be transformed to synthetically important β-amino acids via simple conversions in high isolated yield.A one-pot three-component reaction of isatin derivatives, malononitrile and ketene catalyzed by PPL was established successfully. The effect of enzymes, solvents, water content, catalyst loading, substrate molar ratios and temperatures on reaction yields was investigated in details, and a series of spirocompounds were obtained. PPL exhibited the highest catalytic activity in DMSO. The4-position substituted isatin, cyanoacetamide or ethyl cyanoacetate barely participated in the reaction due to their steric hindrance.Nuclease p1was observed to directly catalyze the asymmetric aldol reactions between isatin derivatives and cyclic ketones. The effect of a series of reaction conditions involving enzymes, solvents, water contents, substrate molar ratios and substrate structure on yields and stereoselectivities were investigated in details. The addition of15%deionized water had a large influence on the enzyme activity. The isolated yields was up to95%, ee value was up to82%and dr value was up to>99/1.In this thesis,84compounds were synthesized including15derivatives of3,4-dihydropyridin-2-one,34products of pyridin-2-one,12spirocompounds,12products of aldol addition,6α-alkylated nitrile derivatives,3ketene compounds,1amino acid intermediates and1β-amino acid. These compounds were characterized by1H NMR,13C NMR, FTIR, and HRMS and56compounds have been confirmed to be new compounds.