Aphids are major pests throughout the world and responsible for several damages to crop plant species not only as a result of their sap taking but also as virus vectors. A single alarm pheromone, (E)-�-farnesene (A  ), was reported to release in most aphid species when they are disturbed. (E)-�-farnesene has been shown to be endowed with multiple biological functions, such as repellent activities and insecticidal properties. However, it is prevented in agriculture applications by its susceptibility to oxidation and its complex and expensive synthesis. Therefore, it is necessary to find its analogues that are more stable and efficient to meet the aphid control in sustainable agriculture. It is understood that the binding mode between ligands and the receptor can provide a great significant guidance to design new compounds with high potency. As a novel molecular interaction in biological molecule, the halogen bonding force was found to play an important part in the binding between small ligand and its receptor. Therefore, a series of (E)-�-farnesene analogues containing a pyrazole moiety with a Cl substitution were designed and synthesized to find some higher activity candidates of pest control agent. The binding affinities to odorant-binding protein (OBP) of pea aphid Acythosiphon pisum (Harris) were evaluated. The binding affinity of (E)-�-farnesene analogues with Cl substitution to OBP7 were higher than those of without Cl substitution. The binding model study showed that a halogen bond interaction indeed contributes to their binding to OBP7 with a distance of 3.23 and 3.16 �, respectively, in Fig.1. The binding score with these (E)-�-farnesene analogues was found to be in good agreement with their binding affinity.It was proposed that the Cl substitution on the (E)-�-farnesene analogues is hopeful to improve the binding affinity to the receptor and further showed good repellent behavior effect on the agricultural pest.

Rational design of novel (E)-�-farnesene analogous with a Cl substitution based on an insect OBP7 crystal structure

248th National Meeting (2014)

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