Nereistoxin analogs

The members of this class of insecticides are all analogs of nereistoxin, a natural toxin of the marine worm Lumbriconcrcis heteropoda. This class includes thiocyclam, cartap, and bensultap. 

Thiocyclam is a selective contact and stomach poison insecticide. It is used for control of Colorado potato beetles, leafminers, rice stem borers on potatoes, cotton, rice, sugarcane, ornamentals, and vegetables. Its oral LD50 in rats is 399 mg/kg. 

Cartap hydrochloride is a broad-spectrum insecticide used for control of coleopterous, lepidopterous, and sucking insects, especially Colorado potato beetles, diamondback moths, rice stem borers, and thrips on rice and vegetables. Its oral LD30 in rats is 345 mg/kg. 

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Thus, the thiol sulfur may act as either a leaving group in car-tap or as an electrophile in bensultap on route to the formation of nereistoxin. Therefore, the number of nereistoxin analogs which may be prepared for insecticidal evaluation is very large. This includes the possibility of derivatives formed from the reaction between 2-dimethylamino-propane-l,3-dithiol and the chlorosulfenyl and chlorosulfinyl intermediates described in Figure 2. 

The nereistoxin analogs (cartap hydrochloride, bensultap, and thiocyclam) are all proinsecticides that must be activated in vivo to become nereistoxin (see Chapter 4, subsection 4.2.12.8 for nereistoxin structure). Nereistoxin acts as an antagonist of the acetylcholine receptor. Unlike with nicotine, insects treated with nereistoxin are rapidly immobilized without convulsive symptoms, possibly because nereistoxin does not induce depolarization (Corbett et al., 1984). 

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