Modular synthesis of the pheromone (2S,7S)-2,7-nonanediyl dibutyrate and its racemate and their field efficacy to control orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae).

Abstract

Sudden outbreaks of the orange wheat blossom midge, Sitodiplosis mosellana (Géhin) cause huge wheat yield losses. Use of sex pheromones is more efficient than laborious egg counting to monitor these hidden-concealed insects. Quick synthesis of the sex pheromones is therefore required to meet the sudden outbreak needs. A synthetic approach of stereospecific and racemic S. mosellana pheromones was presented. This method afforded the stereospecific and racemic S. mosellana pheromones in three steps and high enantioselectivity (> 98% ee for (2S,7S)-2,7-nonanediyl dibutyrate) in less than 1 day with 74% and 73% overall yields, respectively, whereas most conventional methods require longer synthesis time with less than 40% yield. The synthesis routes could quickly and economically afford the pheromones, starting from synthon (S)-but-3-yn-2-ol (1a) or but-3-yn-2-ol (1b), through the same three-step processes of coupling, reduction, and esterification. The Y-tube olfactometer results showed significant attractiveness of the synthetic stereospecific and racemic sex pheromones to S. mosellana males relative to the blank control (P < 0.001). Field trials also demonstrated significant attractiveness of the synthetic stereospecific and racemic sex pheromones relative to the blank control (P < 0.001). This modular approach is conducive to the deployment of field traps and timely responses to S. mosellana outbreaks and can be a time-saving and cost-effective tool to manage S. mosellana. © 2022 Society of Chemical Industry.