"Clicking" fragment leads to novel dual-binding cholinesterase inhibitors

Cholinesterase inhibitors are potent therapeutics in the treatment of Alzheimer's disease. Among them, dual binding ligands have recently gained a lot of attention. We discovered novel dual-binding cholinesterase inhibitors, using "clickable" fragments, which bind to either catalytic active site (CAS) or peripheral anionic site (PAS) of the enzyme. Copper(I)-catalyzed azide-alkyne cycloaddition allowed to effectively synthesize a series of final heterodimers, and modeling and kinetic studies confirmed their ability to bind to both CAS and PAS. A potent acetylcholinesterase inhibitor with IC₅₀ = 18 nM (compound 23g) was discovered. A target-guided approach to link fragments by the enzyme itself was tested using butyrylcholinesterase.

Highly selective inhibition of butyrylcholinesterase by a novel melatonin-tacrine heterodimers

Novel inhibitors of cholinesterases, especially butyrylcholinesterase (BuChE), were obtained by coupling melatonin-tacrine heterodimers via the carbamate bond. Compounds 14a-i possessed potent cholinesterase inhibitory activity (with IC50 values as low as 1.18 nM for acetylcholinesterase (AChE) and 0.24 nM for butyrylcholinesterase (BuChE)). These heterodimers exhibit selectivity toward BuChE, being from 4- to 256-fold more active toward BuChE than AChE, but still acting as better AChE inhibitors than tacrine 4.