Synthesis Biological Evaluation and ComputationalStudies of Tri- and Tetracyclic Nitrogen-Bridgehead Compounds as PotentDual-Acting AChE Inhibitors and hH3 ReceptorAntagonists

摘要

Combination of AChE inhibiting and histamine H3 receptor antagonizing properties in a single molecule might show synergistic effects to improve cognitive deficits in Alzheimer’s disease, since both pharmacological actions are able to enhance cholinergic neurotransmission in the cortex. However, whereas AChE inhibitors prevent hydrolysis of acetylcholine also peripherally, histamine H3 antagonists will raise acetylcholine levels mostly in the brain due to predominant occurrence of the receptor in the central nervous system. In this work, we designed and synthesized two novel classes of tri- and tetracyclic nitrogen-bridgehead compounds acting as dual AChE inhibitors and histamine H3 antagonists by combining the nitrogen-bridgehead moiety of novel AChE inhibitors with a second N-basic fragment based on the piperidinylpropoxy pharmacophore with different spacer lengths. Intensive structure–activity relationships (SARs) with regard to both biological targets led to compound >41 which showed balanced affinities as hAChE inhibitor with IC50 = 33.9 nM, and hH3R antagonism with Ki = 76.2 nM with greaterthan 200-fold selectivity over the other histamine receptor subtypes.Molecular docking studies were performed to explain the potent AChEinhibition of the target compounds and molecular dynamics studiesto explain high affinity at the hH3R.