Design,Synthesis And Biological Evaluation Of Tricyclic Pyrazolo[1,5-c][1,3] Benzoxazin-5(5H)-one Scaffolds As Targeted ChE Inhibitors

Alzheimer’s disease（AD）is a chronic central nervous system degenerative disease characterized by a gradual decline in memory and other cognitive functions.According to the literature,more than 50 million people worldwide suffer from Alzheimer’s disease,and the number of cases is still growing wildly every year.At present,the drugs used in the clinical treatment of Alzheimer’s disease can only temporarily delay the progress of the disease,and can not really improve the disease state,but can not completely cure.In the past few decades,hypothesis of various pathogenesis of AD,such as cholinergic theory,β-amyloid（Aβ）aggregation theory,oxidative stress theory,etc.Among them,cholinergic theory is the most researched and most effective treatment strategy.Due to the limited efficacy and adverse reactions of selective AChE inhibitors,the development of selective BuChE inhibitors has become a hot trend in recent years.（1）In our research,based on the structural analysis of tricyclic scaffolds as butyrylcholinesterase（BuChE）inhibitors,a series of pyrazolo[1,5-c][1,3]benzoxazin-5（5H）-one derivatives were designed,synthesized and evaluated for their acetylcholinesterase（AChE）and BuChE inhibitory activity.（2）We then performed a series of biological and pharmacological activity analyses on the synthesized target compounds,including inhibition of acetylcholinesterase and butyrylcholinesterase by the target compound,and kinetic experiments of butyrylcholinesterase inhibition.,cytotoxicity test and neuroprotective test,determination of oil-water partition coefficient and molecular docking.Some target compounds show selective inhibition of butyrylcholinesterase activity Compounds with 5-carbonyl and 7-or/and 9-halogen substitutions showed potential BuChE inhibitory activity,among which compounds 6a,6c and 6g showed the best BuChE inhibition(IC₅₀=1.06,1.63 and 1.63μM,respectively).The structure–activity relationship showed that the 5-carbonyl and halogen substituents significantly influenced BuChE activity.Compounds 6a and 6g were found nontoxic,lipophilic and exhibited remarkable neuroprotective activity and mixed-type inhibition against BuChE（Ki=7.46 and 3.09μM,respectively）.Docking studies revealed that compound 6a can be accommodated into BuChE via five hydrogen bonds,one Pi–Sigma interaction and three Pi–Alkyl interactions.