Design,Synthesis And Activity Study Of Disubstituted Pyrimidine Amine Antibacterial Synergists

With the discovery and application of penicillin,people are entering a new era of antibiotics,which are also powerful weapons to pathogenic bacteria.The antibiotics has greatly reduced the probability of death from bacterial infections.However,when bacteria are exposed under antibiotics,the resistance to antibiotics is generated,and the effectiveness of antibiotics is reduced or even disappeared.More seriously,some bacteria are resistant to different antibiotics.And antibiotic-resistance bacteria have already become the severe menace to human health.There are different kinds of resistance mechanisms in bacteria,multi-drug efflux pump is known as a universal resistance mechanisms,which exist in nearly all kinds of bacteria.There are different multi-drug resistance mechanisms in different kinds of bacteria.P-glycoprotein(P-gp)efflux pumps expressed in ABC(ATP-binding cassette)superfamily are in Gram-positive bacteria and AcrAB-TolC efflux pump system in the RND(resistance-nodulation-cell division family)superfamily are in Gram-negative bacteria.The role of the efflux pumps expel the antibacterial drugs out bacteria,and form resistance of antibiotics.The efflux pump inhibitor suppress the efflux pump,then elevate the concentration of antibiotics in bacteria and prolong the active time of drugs,which is known as the antibacterial synergistic activity when the inhibitors combined with antibiotics.Therefore,efflux pump inhibitors are one of the effective ways to increase the efficacy of antibiotics.The efflux pump proteins contain abundent hydrophobic amino acid residues,and a wide sprectrum hydrophobic chemicals have binding ability to efflux pump proteins.We found in our previous study that some chalcone derivatives may have inhibition activity to efflux pump.Therefore,we use chalcone as the basic skeleton to design novel efflux pump inhibitors.In order to improve hydrophobicity of chemicals,the long-chain alkyl groups were added.We also found that the middle acryloyl group in chalcone is too flexible,and superabundant comformations weaken the binding ability to efflux pump proteins.In order to fix the conformation and decrease the flexibility,we transform the acryloyl group in chalcone to rigid pyrimidine ring.We also substituted the benzene ring with thiophene ring or furan ring,which are easier to form hydrogen bond and have more-favored pharmacodynamic charecters.Based the above,we designed a chemical library included 28 pyrimidine ring compounds,and then these compounds is processed molecular docking to simulate their binding ability to the efflux pump proteins.The 3D structures of two kinds of proteins for docking simulation were extracted and prepared from Protein Data Bank(PDB),one is 2HYD(PDB code)of P-gp in staphylococcus aureus(Gram-positive bacteria),the other is 5ENO of AcrB in Escherichia coli(Gram-negative bacteria).The final docking scoring of these chemicals are greater than 5(meaning simulation inhibition constant K_i is about?mol),which elucidate the rationality of our design.Subsequently,we synthesized the target compounds in the designed chemical library.First,4-(4-methylpiperazinyl)benzaldehyde and acetyl acyl compounds were synthesized by substitution and F-K acylation reaction.These two compounds were processed alkali-catalyzed aldehyde condensation to synthesize the chalcone intermediate.Then the intermediate were processed alkaline catalysis michael addition to produce the pyrimidine derivatives.Finally,the target products were prepared by acrylation with catalysis of Lewis acid aluminum trichloride.The structures were determined with NMR(1H and 13C)and other spectrum methods.The literature review verified that the 23 compounds are novel.In order to determine the antibacterial synergistic activity of compounds,we established antibiotics-resistance models of Staphylococcus aureus and Escherichia coli.The synergistic activities of the synthesized compounds were evaluated with these two models.The results of part of the synthesized compounds indicated that four compounds show obvious antibacterial synergistic activities to tetracycline-resistance Escherichia coli.These active compounds could be used as lead compounds for the development of new and potent inhibitors to bacterial efflux pumps in future study.