Design, Synthesis And Bioassay Of Novel Compounds Against Several Disease Targets

The dissertation for Ph. D. degree focuses on the design, synthesis and bioassay of novel active compounds against three important drug targets, which areβ-amyloid （Aβ）, acetylcholinesterase （AChE）, and 5-lipoxygenase （5-LOX）, on the basis of the virtual screening and classic design strategies of drug molecules.Aβpeptides adopt a conformation mixture of random coil,β-sheet and/orα-helix in solution, which makes it difficult to design inhibitors based on the 3D structures of Aβpeptides. We thus searched the SPECS database containing 278,000 small molecules via virtual screening technology based on the C-terminalβ-sheet region of an Aβintermediate structure extracted from molecular dynamics simulations of Aβconformational transition. One hundred and twenty five compounds were selected for bioassay according to the scoring data of virtual screening and drug-likeness analysis. Compound A1 and A39 showed potent inhibitory activities against Aβaggregation, the IC₅₀ values are 4.94 mM and 11.92 mM, respectively. Compound A1 and A39 were selected as the model compounds for further structural modification. Totally, 43 new analogues （A1-A43） were designed and synthesized. The bioassay results indicated that compounds A19 andA32, which modified from compounds A1, showed high inhibitory potency of Aβaggregation, and the inhibitory activity of compound A32 (IC₅₀=0.41 mM) was 10 times more potent than that of the model compound A1 (IC₅₀=4.94 mM). Compounds A40, A41, A42 and A43, which modified from compounds A39, also exhibited stronger inhibitory activities than that of the model compound A39.Alzheimer’s disease （AD） is a multifactorial disease caused by genetic, environmental, and endogenous factors. There is, therefore, a strong indication that the development of compounds able to hit multiple targets might disclose new avenues for the treatment of AD. In chapter two, we adopted molecular hybridization strategy to design rationally and finally synthesize 46 new hybrid compounds based on the pharmacophoric sub-unities of the known AChE inhibitors and our previous researched Aβaggregation inhibitors through the click-chemistry method. Up to now, 9 compounds of them have been finished to evaluate their inhibitory activities toward Aβaggregation. Surprisingly, 7 compounds exhibited potent inhibitory activities against Aβfibril formation, and the inhibitory activities of compounds B41, B44 and B45 increased～50 times than that of the reference compound DC-AB1, with IC₅₀ values 0.18 mM, 0.17 mM and 0.19 mM, respectively. The other bioassays for AChE inhibitory activities and AChE-induced Aβaggregation inhibitory activities are in progress.It is reported that 5-Lipoxygenase （5-LOX） is the key enzyme in the conversion of arachidonic acid （AA） to the bioactive Leukotrienes （LTs）. In the chapter three, a series of pyrazole derivatives possessing potential 5-LOX inhibitory activity were designed and synthesized by the classic design strategies of drug molecules and the active pocket of the homology modeling 3D model of 5-LOX. The subsequent biological evaluation suggested that nine compounds （C3, C5, C7, C10, C11, C16, C17, C20 and C23） were proven to be more effective than the reference compound Zileuton in the PMNL bioassay and five compounds （C5, C7, C16, C17 and C20） exhibited more potent inhibitory activities than Zileuton in the HWB bioassay. In Chapter four, the SPECS database containing 278,000 small molecular compounds was searched by virtual screening technology according to the active pocket of the three-dimensional model of 5-LOX, and thirty two compounds were selected for bioassay according to the scoring data of docking and drug-likeness analysis. Compound D1 showed potential inhibitory activity against 5-LOX, its IC₅₀ values in PMNL and HWB bioassay is 0.97μM and 30.89μM, respectively, and thus was selected as the model compound for further structural modification. 13 pyrimidine derivatives were designed, synthesized and evaluated by PMNL and HWB for their inhibitory activities against 5-LOX. All derivatives showed inhibitory activities against 5-LOX at the concentration of 5μM. Three of them （D1, D2 and D6） exhibited the most potent inhibitory activities compared to that of the control drug （Zileuton） in the PMNL bioassay, and also presented excellent inhibitory activities in the HWB evaluation. The results of molecular modeling study were in accordance with the experimental results quite well. The excellent activities of these compounds showed that they may possess potency for the treatment of LT-related diseases.2-（3-Chlorophenyl）-4-aminoquinoline, as a key intermediate in the synthesis of novel chmical inhibitors of human cyclophilin A, was not obtained by reduction of 2-（3-chlorophenyl）-4-nitro-quinoline with Sn and concentrated HCl in refluxing ethanol. A de-nitro product 2-（3-chlorophenyl）-quinoline was identified by ¹H NMR and MS. To investigate the scope of this reaction, we designed and synthesized 14 substrates for this research, by which a plausible mechanism was proposed in chapter five.The outbreaks of AIV such as the H5N1 subtype virus in recent years, the increasing geographic distribution of this epizootic virus and its ability to transfer to humans and cause severe infection have aroused serious concerns regarding the control measures that should be undertaken to curb a potential pandemic of this disease. Here, zanamivir was synthesized by using N-acetylneuraminic acid as the starting material, through a eight-step process including esterification, acylation, cyclization, ring-opening, azide substitution, reduction, and hydrolysis followed by reaction with aminoiminomethanesulfonic acid （AIMSA）. The target compound was verified by ¹H NMR, ¹³C NMR, LR-MS, HR-MS, Elemental Analysis and X-ray. The total yield is 10.1%.In summary, on the basis of the structural-based virtual screening approach in conjunction with chemical synthesis and bioassay, we have designed and synthesized one hundred and thirty compounds targeting three important drug targets. Several novel scaffolds with potent activities have been identified, which provided some new templates to discover new chemical entities.