Absolute Configuration\nof the Invasive Mealybug Delottococcus aberiae (De Lotto) Sex Pheromone: Synthesis\nand Bioassay of Both Enantiomers

The mealybug Delottococcus aberiae (De Lotto) (Hemiptera: Pseudococcidae) is an invasive pest reported\nin Europe at the end of the first decade of the 2000s, causing severe\ndamage to citrus production in eastern Spain. In a previous work,\n(4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)methyl acetate was\nidentified as the sex pheromone emitted by females, a new compound\nwith an unusual β-necrodol skeleton possessing one stereocenter.\nThis compound was assigned to the (−)-enantiomer but the absolute\nconfiguration was then not reported. In the present study, enantiomeric\npure samples of both enantiomers were synthesized. X-ray diffraction\nanalysis allowed the (−)-enantiomer, identical to the one emitted\nby virgin D. aberiae females, to be\nunequivocally identified as (−)-(<i>R</i>)-(4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)methyl\nacetate. Bioassays carried out to test the activity of both enantiomers\nunder field conditions suggest that the presence of the (+)-(<i>S</i>)-enantiomer has detrimental effects on the activity of\nthe racemates.