Design,Synthesis And Pharmacodynamic Study Of Novel Dihydropyrazole MurA Enzyme Inhibitor

As the great drug discovery in 20^thcentury,the antibacterial and antibiotics have saved countless lives in clinic.However,as the clinical application of antibiotics,the antimicrobial resistance became more and more serious.Antimicrobial resistance leads lower efficiency and narrower antimicrobial spectrum of antibacterial and antibiotics.So,the therapeutic gap has already appeared in anti bacterial infections.Therefore,it is urgent for us to develop new antibacterial to deal with the existing mechanisms of antimicrobial resistance.Unlike human and other mammals,the bacterial cell contain cell wall,so those enzymes in the biosynthetic pathway of bacterial cell wall have always been potential new targets for the development of low toxicity and side-effect antimicrobial drugs.The presented thesis is studied one new type of enzyme inhibitors to interfere the the synthesis of cell wall in bacterial.The main research contents of this subject are as follows:1.Design of target compounds:In this study,MurA,one enzyme in the bacterial peptidoglycan biosynthesis pathway,was selected as the drug target:（1）MurA enzyme is the enzyme in the first step of bacterial peptidoglycan biosynthesis pathway.（2）Pyrazole and its derivative is one kind of nitrogen-containing five-membered heterocyclic ring and have been reported to have anti-bacterial activity.In this project,the pyrazole ring was designed as the basic skeleton,with computer-aided drug design software and the method of active substructure splicing,20 new dihydropyrazole of 4 series MurA enzyme inhibitors were designed and screened.Then,its biological activity is predicted by molecular docking and Co MFA model.The prediction results(The scores of molecular docking are all greater than 5,PIC_50pred<5)show that the compounds we designed have a certain biological activity and are valuable.2.Synthesis of target compounds:The 19 novel dihydropyrazol-like MurA inhibitors were synthesized with key intermediate ofα,β-unsaturated ketones,and the synthesis processes were consisted of three steps.Step one:Different substituents were introduced into aromatic aldehydes and ketones.Step two:Chalcone intermediate was produced by condensation of carbonyl aldehyde under strong base catalysis.Step three:Chalcone reacts with hydrazine by cyclization to form pyrazole ring,and then the aliphatic acid chain is introduced by amidation reaction.In this synthesis process,carboxylic acid or acyl chloride were used as the acylating agents for different target compounds respectively.Finally,structures of compounds were determined by NMR and other spectrum methods.3.Pharmacodynamic study of target compounds:We used MTT experiments to screen the antibacterial activity of those compounds against E.coli,Staphylococcus aureus and methicillin-resistant Staphylococcus aureus,the experimental results show that our design is in right way.The four series of compounds show a certain inhibitory activity on both Gram-positive and Gram-negative bacteria:the MIC value of C and D series compounds for the three bacteria ranged from 100-600nM.The MIC value of some compounds in series A and B was less than 1μM,and the best one（compound M-A-5）could reach 66.7nM.In summary,a series of novel dihydropyrazole MurA inhibitors have been designed and synthesized by computer-aided drug design,and a series of leading compounds with potential antibacterial activity have been preliminarily screened through antibacterial experiments,in order to provide help for further research to discover new MurA inhibitors in the future.