Synthesis of phosphotriester by DCC and its biological activities

The synthesis of a phosphotriester, an inhibitor of acetylcholinesterase, was performed by the coupling reaction of diethylphosphate with various phenolic compounds using dicyclohexylcarbodiimide (DCC). All of the compounds synthesized inhibited housefly acetylcholinesterase activity. Derivatives including an electronegative part as a nitro group in the phenol ring showed strong inhibition towards housefly acetylcholinesterase, but those with hydrophobic derivatives of the phenol group, such as cresol, naphthol and biphenol, showed relatively low inhibition. In experiments with housefly, the value of LD50 for each chemical correlated with the I50 value for acetylcholinesterase except alpha-naphthyl diethylphosphate, beta-naphthyl diethylphosphate and p,p'-biphenyl diethylphosphate.