Among the most noxious materials made by man are the organophosphorus chemical- warfare materials, such as the phosphonofluoridate G agents soman (1) and sarin (2) and the phosphonothioate V agents, such as VX (3).[2] The latter is particularly toxic [3] because it is N-protonated at physiological pH and is therefore well accommodated by the acetylcholine esterase active site, which it inhibits through irreversible phosphonyl transfer ...