Studies On The Total Synthesis Of Spirotryprostatins Derivatives And The Evaluation Of Biologiacl Activities

Indole diketopiperazine alkaloids(indole DKPs)are natural products isolated from secondary metabolites of endophytic fungi,especially in the genera Aspergillus and Penicillium of the phylum Ascomycota or sac fungi.The alkaloids can be divided into tryprostatins,cyclotryprostatins and spirotryprostatins.Among them,spirotryprostatins is a kind of compounds with special and complex structure.The spirotryprostatins are characterized by a unique spiro-oxindole-substituted cis-prolyl-tryptophanyl-diketopiperazine.The synthesis of spirocyclic compounds is trouble some due to the poor predictability of stereochemical control of cyclic systems.This problem can be particularly for the diastereoselective construction of spiroquaternary carbon centers.The spirotryprostatins not only have a class of naturally occurring privileged structures but also exhibit a broad spectrum of biological activities that make them attractive scaffolds for drug discovery.The indole DKPs contain two moieties indole and cyclic dipeptides.These intriguing structures provide wide range of biological activities,such as antimicrobial,anticancer,anti-inflammatory,antioxidant,and insecticidal activities.Recently,the discovery of these activities has spawned numerous investigations into their synthesis.Although,there are a large number of indole DKPs obtained by the extraction and separation of natural products,their productivity is very low.Therefore,the efficient synthesis of these natural products,especially the asymmetric synthesis of the chiral natural products,is of great significance in the field of synthetic chemistry and pharmaceutical chemistry.In order to establish a simple and efficient asymmetric total synthesis method of spirotryprostatin compounds,expand the library of these compounds,and explore indole diketopiperazine alkaloids biological activities,this paper is divided into the following parts.(1)A rapid,simple and practical procedure for the synthesis of spirotryprostatins compounds was described.A series of spirotryprostatins were synthesized utilizing a highly enantioselective 1,3-dipolar cycloaddition,this cyclization reaction between the azomethine ylide dipolar and(E)-3-arylideneindolin-2-ones.Then,by two-phase synthesis,S chotten-B aum ann reaction between L-proline chloride protected by N-Fmoc and spironolylpyrrolidine intermediate was used to obtain dipeptide intermediate.After that,deprotection and cyclization reaction were carried out to obtain the final product with a total yield of 42%.An asymmetric synthesis route of spirotryprostatins was established.(2)A series of stereochemically complex spiro[pyrrolidin-3,3'-oxindole]s with spiro quaternary stereogenic centers in good to excellent yields(up to 85%),excellent levels of enantioselectivities(up to 93%ee)were obtaind.Three chiral ligands were used in the highly efficient asymmetric 1,3-dipolar cycloaddition respectively,including(S)-TF-BiphamPhos/AgOAc,(S)-t-Bu-BOX/AgOAc and(S)-MonoPhos/AgOAc.The latter two were first repoted to catalyzed the cyclization of azomethine ylide dipolar and(E)-3-arylideneindolin-2-ones.The products catalyzed with(S)-TF-BiphamPhos/AgOAc were different with the latter two ligands.Two kinds of spiro[pyrrolidin-3,3'-oxindole]s core were obtained in these reactions,one is(2'R,3S,4'R,5'R),and the other is(2'S,3R,4'S,5'S).In these there chiral ligands,Excellent yields(up to 85%)was obtained by(S)-MonoPhos/AgOAc and good enantioselectivities(up to 93%ee)was obtained by(S)-t-Bu-BOX/AgOAc.These key reactions assemble the spirooxindole core stereoselectively and provide methods for the preparation of diverse and complex chiral pyrroloindoline compounds.(3)The two starting materials of the whole synthesis route are glycine and Isatin,which are commonly used in the synthesis of pharmaceutical compounds.16 kinds of dipolar and 13 kinds of dipolarophile compounds were prepared,the yield of the two compounds is high,the highest yield is 91%.The stereoselectivity of the product is good,and the solvent of the reaction is environmental protection.The products of these two reactions are easy to be purified(without silica gel column chromatography).(4)All compounds were characterized by 1H-NMR,13C-NMR,ESI-HRMS,and the stereochemistry configuration were analysized via 2D NMR and X-ray diffraction analysis.The ee values of enantioselectivity of spiro intermediates were determined by HPLC.The spectra of compounds 1b,2a,4d-3c,4f-3f,4h-3a and 5c were analyzed in this thesis.(5)The discovery of increasing numbers of new indole DKPs have led to an expanding range of bioactivities.In the sixth part,the antimicrobial activity and structure-activity relationship(SAR)of 24 indole DKPs were explored.Compounds A7 and A8 were found to be the most active,with minimum inhibitory concentrations(MIC)values in the range of 0.39-3.13?g/mL against the four tested bacteria(Staphylococcus aureus,Bacillus subtilis,Pseudomonas aeruginosa and Escherichia coli).Furthermore,spirotryprostatins C1 and C2 displayed broad-spectrum antimicrobial activity with MIC values of 0.39-12.5?g/mL against all tested bacteria and plant pathogenic fungi(Colletotrichum gloeosporioides,Valsa mali,Alternaria alternata and Alternaria brassicae).(6)According to the in silico study,compounds A8 showed significant binding affinity to the FabH protein from Escherichia coli,which has been identified as the key target enzyme of fatty acid synthesis(FAS)in bacteria.Therefore,based on the biological assay data and molecular docking,there could be some correlation between the bioactivity and the FabH inhibitory activity of these compounds.(7)The synthesized spirotryprostatins with certain cytotoxicity to A549 cells,PC3 cells and HepG2 cells.These experimental results could provide useful reference for thesynthesis and drug discovery of spirotryprostatins.Through the above research,this paper provides a new method for the synthesis of spirotrotrotrostatins and enriches the library of this kind of compounds.At the same time,the analysis of biological activity and activity mechanism of this kind of compounds in this paper provides a reference and theoretical basis for the research and development of antibacterial drugs.