Tricyclic pyrazolo[1,5-d][1,4]benzoxazepin-5(6H)-one scaffold derivatives: Synthesis and biological evaluation as selective BuChE inhibitors

Abstract

BuChE inhibitors play important roles in treatment of patients with advanced Alzheimer's disease (AD). A series of tricyclic pyrazolo[1,5-d][1,4]benzoxazepin-5(6H)-one derivatives were synthesized and evaluated as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Some derivatives showed selective BuChE inhibitory activity, which was influenced by the volumes of the substituted groups at the C6 position and halogen substituents at the benzene ring of tricyclic scaffold. Among them, compounds 3f and 3o with dihalogen and 6-ethyl substituent showed the most potent activity (IC50 = 2.95, 2.04 μM, and mixed-type, non-competitive inhibition against BuChE, respectively). Eutomer (6R)-3o exhibited better BuChE inhibitory activity than (6S)-3o. Compound 3o exhibited nontoxic, good ADMET properties, and remarkable neuroprotective activity. Docking studies revealed the same binding orientation within the active site of target enzyme. Compound 3o was nicely bound to BuChE via three hydrogen bonds, one Alkyl interaction and three Pi-Alkyl interactions. The selective BuChE inhibitors had a potential use in progressive neurodegenerative disorder.