New Acetylcholinesterase Inhibitor Design, Synthesis And Bioassay

Alzheimer's disease(AD),which is characterized by progressive loss of memory and impairment in cognition,is becoming a serious threat to life expectancy for elderly people.Current clinical therapy for AD patients is mainly palliative treatment targeting acetylcholinesterase(ACHE).Recently ACHE,particularly the peripheral anionic sites(PAS),was indicated to be involved in Aβpeptide aggregation-promoting action and created a steady compound with Aβ,which is more neurotoxicity than Aβ.Thus,AChE inhibitors,which simultaneously block both the catalytic and PAS,might not only alleviate the cognitive deficit of AD patients by elevating ACh levels, but also act as disease-modifying agents delaying amyloid plaque formation. Such ACHE inhibitors are becoming a new field for AD therapy.In this thesis,a type of cordalis alkaloid corydaline,which has demonstrated moderate inhibition to ACHE,was used as a lead compound to obtain the action mechanism of corydaline to ACHE and screen a series of its open ring derivatives by means of molecular docking and virtual screen. Based on these virtual screening results,4 derivatives with high potential activity were synthesized and characterized,also the target compoundsⅠ₁～Ⅰ₄ and the key intermediatesⅥ₁～Ⅵ₄ was tested for their ACHE inhibitory activity in vitro.Molecular docking method(GOLD) was used to investigate the binding mode of corydaline with acetylcholinesterase and to screen a series of open ring derivatives with different carbon linkages and different substituent groups.The best result was obtained by GOLD when corydaline was bound to the enzyme catalytic site in an open conformation.The conformation model indicates that phenyl ring A interacts with the phenyl group of Tyr 334 via a classic parallelπ-πaccumulation and that the positively charged nitrogen atom interacts with the phenyl group of Phe 330 in the hydrophobic site by the cation-πeffect.Phenyl D that penetrate to the catalytic position at the bottom of the active pocket,interact with Trp 84 viaπ-πeffect.Virtual screening showed that the scores of most derivatives were higher than that of corydaline,and the 15 open ring substances with the highest scores were mainly derived from those substituted by phenoxy groups and those with 2-to 7-carbon linkages.18 Compounds including 4 target compounds with 3,4-dimethoxyl-benzaldehyde as starting reagent were totally synthesized.The whole synthesis steps including condensation,addition,reduction,cyclization, acylation and reduction.The purity of the compounds was checked by TLC and HPLC,and the structures were confirmed by ¹HNMR,IR and elemental analysis.Additionlly,the synthetic technics of 3,4-dimethoxyl-phenylacetic acid from 3,4-dimethoxyl-benzaldehyde was optimized by the steps of condensation,reduction and oxidation and the yield was improved to 62.6% from previously 45.0%.The target compoundsⅠ₁～Ⅰ₄ and the key intermediatesⅥ₁～Ⅵ₄ were tested for their AChE inhibitory activity in vitro.All of them exhibited high AChE inhibitory activity and 5 of them are higher than Positive control drug galanthamine,especially compoundⅠ₂ has almost 225 times more inhibition activity as compared to galanthamine.Pharmacokinetics and toxicity of compoundsⅠ₁～Ⅰ₄,Ⅵ₁～Ⅵ₄, corydaline and galanthamine was predicted by Pallas.All the compouds possess good pharmacokinetic characteristics,and the toxicities do not increase as compared to lead compound,showing good drugability.Therefore, it's a very promising lead compounds for the treatment of AD.