Nephotettix cincticep

Asperparaline A (123) showed remarkable insecticidal activity against third instar larvae of Nilaparvata lugens, third instar larvae of Nephotettix cincticeps, and the adults of Musca domestica. 

One of the major pest Insects in rice fields is the green rice leafhopper (Nephotettix cincticeps). Recently acquired resistance to carbamate insecticides has greatly complicated control of this insect. Resistance can develop by a number of different mechanisms such as cuticle thickening to Impede transport, enhanced metabolic degradation or molecular changes within the target enzyme (AChE) (1 ). In the case of carbamate insecticides, resistance occurs mainly at the target enzyme which expresses reduced sensitivity to the inhibitors (2). 

Table 2. Anti-AChE activity of N-aryl oxadiazolones on susceptible(S) and resistant(R) Nephotettix cincticeps...

Whereas S. B. Soloway had originally assumed that the for insecticidal activity critical nitromethylene unit would have to be attached to a heterocycle, scientists at Takeda Chemicals were able to show that acyclic compoimds possessed good insecticidal properties as well. They developed a product to control two important pests in rice, both are cicada species the brown planthopper (Nilaparvata lugens) and the green rice leafhopper Nephotettix cincticeps) (Fig. 8.45). 

The brown planthopper (Nilaparvata lugens) (left) and green rice leafhopper (Nephotettix cincticeps) (right). 

Optimisation at the cationic centre led to open-chain nitroguanidines, among which the monomethylated derivatives revealed outstanding activity, while other substitution patterns of the nitroguanidine possessed a species-de-pendent insecticidal profile. Whereas the sensitivity of Nephotettix cincticeps towards analogues with an additional acetyl-, benzoyl- or methylcarbamate-substituent, was approximately the same in comparison to the parent compound, Laodelphax striatellus (the small brown planthopper) proved clearly less sensitive. Careful analysis of the data led eventually to the decision, which structure to select and develop further (Fig. 8.55 and Tab. 8.3). 

Nephotettix cincticeps and Laodelphax striatellus X,Z = H Y Me > Et > H, higher alkyl... 

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