O, S-Dimethylphosphoramidothioate (methamidophos) and N-acetyl O, S-dimethylphos- phoramidothioate (acephate) were synthesized by new methods to investigate the structure– activity study of acetyl cholinesterase (AChE) inhibition through the parameters of log P, δ 31P, and IC50. After their characterization by NMR (31P, 31P {1H}, 13C, and 1H), IR, and mass spectroscopy, log P and δ 31P (31P chemical shift in NMR) were used to evaluate ...