Synthesis, biochemical evaluation, and molecular modeling of organophosphate-coumarin hybrids as potent and selective butyrylcholinesterase inhibitors.

A small library of new organophosphorylated warfarins and 3-benzylcoumarins were synthesized and evaluated for in vitro cholinesterase inhibition by Ellman's method. Most of the compounds were found to be selective for butyrylcholinesterase (BChE) over acetylcholinesterase (AChE), with IC values ranging from 0.363 μM to 53.0 μM determined after 15 s of enzyme exposure. Comparison of the most potent compound, 3b with its constitutional isomer 2b revealed the high importance of phosphate positioning. Reversed selectivity and a 100-fold reduction in anti-BChE activity was observed when the organophosphate was attached to the benzyl instead of the coumarin. Docking calculations suggest that 3b binds initially as a transition state mimic with near-optimal phosphate orientation relative to S198 and occupation of the oxyanion hole prior to phosphorylation. These results might inspire the design of a new type of non-neuropathic and irreversible coumarin-based inhibitor against BChE.