New thienyl- or chlorophenyl-substituted thiazolopyrimidine derivatives and their derived sugar hydrazones incorporating acyclic d-galactosyl or d-xylosyl sugar moieties in addition to their per-O-acetylated derivatives were synthesized. Heterocyclization of the formed sugar hydrazones afforded the derived acyclic nucleoside analogues possessing the 1,3,4-oxadiazoline as modified nucleobase via acetylation followed by the cyclization process. The cytotoxic activity of the synthesized compounds was studied against human breast cancer MCF7 and MDA-MB-231 cell lines as well as human colorectal cancer HCT 116 and Caco-2 cell lines. High activities were revealed by compounds 1, 8, 10, 11, and 13 against Caco-2 and MCF7 cells in addition to moderate activities exhibited by other compounds against HCT116 or MDA-MB-231 cells.

Background: Alzheimer’s disease (AD) is characterized by cholinergic dysfunction, making the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) critical for improving cholinergic neurotransmission. However, the development of effective dual inhibitors remains challenging. Objective: This study aims to synthesize and evaluate novel pyridazine-containing compounds as potential dual inhibitors of AChE and BuChE for AD treatment. Methods: Ten novel pyridazine-containing compounds were synthesized and characterized using IR, ¹H NMR, and ¹³C NMR. The inhibitory activities against AChE and BuChE were assessed in vitro, and pharmacokinetic properties were explored through in silico ADME studies. Molecular dynamics simulations were performed for the most active compound. Results: Compound 5 was the most potent inhibitor, with IC₅₀ values of 0.26 µM for AChE and 0.19 µM for BuChE, outperforming rivastigmine and tacrine, and showing competitive results with donepezil. Docking studies revealed a binding affinity of −10.21 kcal/mol to AChE and −13.84 kcal/mol to BuChE, with stable interactions confirmed by molecular dynamics simulations. In silico ADME studies identified favorable pharmacokinetic properties for compounds 5, 8, and 9, with Compound 5 showing the best activity. Conclusions: Compound 5 demonstrates strong potential as a dual cholinesterase inhibitor for Alzheimer’s disease, supported by both in vitro and in silico analyses. These findings provide a basis for further optimization and development of these novel inhibitors.

Thienopyrimidine derivatives are emerging as potent scaffolds for cholinesterase inhibition in Alzheimer’s disease therapy. In this work, a novel series of substituted thieno[2,3-d]pyrimidines was synthesized via Gewald’s reaction, followed by cyclization and functionalization through nucleophilic substitution and hydrazone formation. Structural confirmation was achieved using spectroscopic techniques, and biological evaluation was performed against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), with donepezil and rivastigmine as reference drugs. Compound 4 emerged as the most potent and selective AChE inhibitor (IC₅₀ = 0.58 µM), while compound 7 also showed strong AChE inhibition (IC₅₀ = 0.63 µM). Notably, compound 9 exhibited superior BChE inhibition (IC₅₀ = 3.05 µM) compared to donepezil (IC₅₀ = 8.41 µM). Dual inhibitory activity was observed for compounds 5, 6, and 11, highlighting their multitarget potential. Molecular dynamics simulations (200 ns) and MM/GBSA binding free energy calculations provided mechanistic insights. Compound 4 showed the most favorable binding energy (ΔGbind = −59.16 kcal/mol), driven by hydrogen bonds with Tyr121 and Glu199 and π-π stacking with Trp83. Residue-level decomposition identified Tyr121, Trp83, Glu199, and Tyr338 as critical contributors to binding stability. Structure–activity relationship analysis confirmed that nitrogen-containing substituents and cyclic amino moieties enhance potency, whereas bulky aromatic groups reduce activity. These findings establish thieno[2,3-d]pyrimidine derivatives as promising candidates for the development of next-generation anti-Alzheimer agents.