Donepezil-melatonin hybrids as butyrylcholinesterase inhibitors: Improving binding affinity through varying mode of linking fragments.

Hybrid inhibitors of acetyl- and butyrylcholinesterase are compounds that combine structural motifs of two different classical inhibitors, leading to a dual binding ligand. A rapidly growing collection of those compounds involves a wide diversity of structural motifs, but the way of linking two active fragments and its impact on the affinity toward cholinesterases usually remains beyond the extent of investigation. We present hereby a detailed analysis of this aspect using melatonin-donepezil hybrids. A new series of compounds, in which two fragments are connected using a carbamate linker, exhibits excellent activity and selectivity toward butyrylcholinesterase.