Nereistoxin

Nereistoxin is a natural product identified in 1962 as the toxic organic compound N,N-dimethyl-1,2-dithiolan-4-amine. It had first been isolated in 1934 from the marine annelid Lumbriconereis heteropoda and acts by blocking the nicotinic acetylcholine receptor. Researchers at Takeda in Japan investigated it as a possible insecticide. They subsequently developed a number of derivatives that were commercialised, including those with the ISO common names bensultap, cartap, thiocyclam and thiosultap.

Structures and synthesis

Bensultap (R=SO2Ph) was made by the reaction of the sodium salt of benzenethiolsulfonate (PhSO2SNa) with N,N-dimethyl 1,3-dichloro-2-propylamine or N,N-dimethyl 2,3-dichloropropylamine in ethanol.

Bensultap can be converted to nereistoxin by treatment with alkali.

History

Japanese fishermen used the annelid worm Lumbriconereis heteropoda as bait but after accidental human poisonings the chemical agent responsible was identified and named nereistoxin. In the 1960s, researchers at Takeda Chemical Industries synthesised the active material N,N-dimethyl-1,2-dithiolan-4-amine and derivatives in which the sulfur-sulfur bond of the 1,2-dithiolane ring was replaced by alternative sulfur-linked groups. The resulting compounds were in many cases less toxic to mammals than the natural product while retaining good activity on insects. It was subsequently shown that all the compounds which were commercialised acted by being propesticides — breaking down in the environment to nereistoxin or a toxic dithiol.