Synthesis and bioactivity of (13Z,15E)‐octadecadienal: A sex pheromone component from Micromelalopha siversi Staudinger (Lepidoptera: Notodontidae)

BACKGROUND: Micromelalopha siversi (Staudinger) (Lepidoptera: Notodontidae) is a defoliator of poplar trees, Populus spp. (Salicaceae). In our previous study, 13,15‐octadecadienal has been conformed as a female‐produced candidate sex pheromone component of M. siversi, but the Z/E stereochemistry of the 1,3‐diene system has not been identified so far. RESULTS: Four unsaturated aliphatic aldehydes, Z13,E15‐18:Ald, Z13,Z15‐18:Ald, E13,E15‐18:Ald, and E13,Z15‐18:Ald, were synthesized from the commercially available 12‐bromo‐1‐decanol mainly by alkylation of lithium alkyne, normal Wittig or Wittig–Schlosser olefination, and hydroboration‐protonolysis. According to gas chromatography (GC) analysis of pheromone gland extracts, Z13,E15‐18:Ald was the main component, and a small amount of Z13,Z15‐18:Ald was also detected, with a ratio of approximately 7:3. However, the results of GC‐electroantennographic detection (GC‐EAD) showed that Z13,E15‐18:Ald was the only compound with electrophysiological activity, whereas Z13,Z15‐18:Ald elicited no activity. In the field, traps baited with only Z13,E15‐18:Ald resulted in much superior results to those with Z13,Z15‐18:Ald as well as the Z13,E15‐18:Ald and Z13,Z15‐18:Ald binary mixture. CONCLUSIONS: Based on geometrically selective synthesis and bioactivity tests, the active sex pheromone component of M. siversi has been identified as Z13,E15‐18:Ald, the pheromone component that has not been identified in Lepidoptera before. The synthetic component was attractive to male moths in preliminary field traps, which provides novel technologies to monitor and control this pest.