Total Synthesis, Stereochemical Assignment, and Field-Testing of the Sex Pheromone of the Strepsipteran Xenos peckii.

The sex pheromone of the endoparasitoid insect Xenos peckii (Strepsiptera: Xenidae) was recently identified as (7 E,11 E)-3,5,9,11-tetramethyl-7,11-tridecadienal. Herein we report the asymmetric synthesis of three candidate stereostructures for this pheromone using a synthetic strategy that relies on an sp3-sp2 Suzuki-Miyaura coupling to construct the correctly configured C7-alkene function. Comparison of 1H NMR spectra derived from the candidate stereostructures to that of the natural sex pheromone indicated a relative configuration of (3 R*,5 S*,9 R*). Chiral gas chromatographic (GC) analyses of these compounds supported an assignment of (3 R,5 S,9 R) for the natural product. Furthermore, in a 16-replicate field experiment, traps baited with the synthetic (3 R,5 S,9 R)-enantiomer alone or in combination with the (3 S,5 R,9 S)-enantiomer captured 23 and 18 X. peckii males, respectively (mean±SE: 1.4±0.33 and 1.1±0.39), whereas traps baited with the synthetic (3 S,5 R,9 S)-enantiomer or a solvent control yielded no captures of males. These strong field trapping data, in combination with spectroscopic and chiral GC data, unambiguously demonstrate that (3 R,5 S,9 R,7 E,11 E)-3,5,9,11-tetramethyl-7,11-tridecadienal is the X. peckii sex pheromone. [ABSTRACT FROM AUTHOR]