BCHE and early-onset autosomal dominant Alzheimer disease: A novel series of 4‐(diethylamino)salicylaldehyde‐based thiosemicarbazone derivatives 5(a–u) were synthesized and screened for their potential against Alzheimer's disease, by testing for their inhibitory effects against cholinesterases (AChE and BChE) and monoaminoxidase A (MAO‐A) and B (MAO‐A).