Development Of Multicyclic Peptide Templates And Peptide Probes Through Stable Thioether-bond

Proteins participate in most of biological and pathological processes in cells via catalyzing different kinds of reactions or via thousands of protein-protein interactions.Consequently,investigate and control over inappropriate proteases expression and protein-protein interactions are important for better understanding of biology systems and can potentially be the effective strategy for therapeutic intervention.Peptide modulators combine the advantages of protein and small-molecules,such as easy to synthesis and modify,binding to proteins with high specificity.On this basis,benefit from being structurally constrained,cyclopeptides,especially multicyclic peptides are farther stable to enzymatic hydrolysis,rigid and with better binding affinity.As a result,they are promising protein inhibitors and ligands.Nature most frequently use disulfide bonds to stabilize the structure and function of proteins and peptides,these molecules also provide various motifs for peptide cycliazation.However,disulfide bonds can be reduced in cytoplasm and can be isomerized in the presence of other thios,thus limit their applications.To solve the problem,chemists developed many strategies of peptides cyclization,among which thioether bond produced via thios in the peptides is much easier to operate,mild and efficient.In this work,we aimed to develop some hyper-rigid and stable multicyclic peptide templates and bioactive peptides based on the thioether bond.We mainly get multicyclic peptides via the reaction of a small phenyl molecule 2,3,5,6-tetrafluoro terephthalonitrile(4F-2CN)and linear peptides contain some thios and N-terminal cysteine.This reaction is programmed and can gradually turn to the only tetra-substitution product.Furthermore,we rigidify the peptide structure by constraining one of the loops at the C-terminus with ’PenXC’ motif.Using this strategy,we get stable bioactive cyclopeptides with high affinity to inhibite protein-protein interactions as well as high stability.Besides,in order to further modulate the configuration of cyclopeptides,we try to use thioether bonds which as the most similar size as natural disulfide bonds to develop peptide templates.This thesis comprises four chapters listed below:Charpter1:The first chapter is a literature review.Initially,we introduced the mechanism of proteases and protein-protein interactions,explained the remarkable properties of cyclopeptides as proteases inhibitors and PPI regulators.Then we gave a detailed introduction on the three classes of strategies of peptides cyclization,as well as some cyclic peptide drugs on the market.On this basis,we introduced the research topic and significance.Charpter 2:We discovered that a small molecule 4F-2CN can react with different kinds of template peptides contain a N-terminal cysteine with some thios.We investigated in detail of the reaction properties among them,identified their reaction mechanisms,as well as the range of application.Charpter 3:On the basis of Charpter 2,we used 4F-2CN to systhesize a series of bioactive multicyclic peptides aimed to inhibite proteases(uPA)or some PPIs(p53-MDM2&Keapl-Nrf2).As same as the template peptides,they all react with 4F-2CN and convert into the only final-product with definite structures.Most of all,in the case of bioactive tricyclic peptides binding to Keapl,we get the result with both hyper rigidity and high binding affinity.Charpter 4:We designed to use the reaction of Cys 的巯基 and α,β-unsaturated amino acid dehydroalanine(Dha)to achieve multicyclic peptides in which the thioether bonds are as the most similar size as natural disulfide bonds.We synthsised the masked amino acid of Dha,Fmoc-Sec(Ph)-COOH,succeeded in coupling it into the peptides during SPPS and then converting it into Dha.Follow-on work is still underway.