2,3-Dihydrohomofarnesal: Female Sex Attractant Pheromone Component of Callosobruchus rhodesianus (Pic)

Abstract

Callosobruchus rhodesianus (Pic) (Coleoptera: Chrysomelidae: Bruchinae) is a pest of stored legumes through the Afro-tropical region. In laboratory bioassays, males of C. rhodesianus were attracted to volatiles collected from virgin females. Collections were purified by various chromatographic techniques, and the biologically active component isolated using gas chromatographic-electroantennographic detection analysis. Gas chromatography-mass spectrometry and NMR analyses suggested that the active compound was 2,3-dihydrohomofarnesal, i.e., 7-ethyl-3,11-dimethyl-6,10-dodecadienal. The structure was confirmed by non-stereoselective and enantioselective total synthesis. Using chiral gas chromatography, the absolute configuration of the natural compound was confirmed as (3S,6E)-7-ethyl-3,11-dimethyl-6,10-dodecadienal. Y-tube olfactomter assays showed that only the (S)-enantiomer attracted males of C. rhodesianus. The (R)-enantiomer and racemate did not attract males, suggesting that the (R)-enantiomer inhibits the activity of the natural compound. In combination with previous reports about sex attractant pheromones of congeners, we suggest that a saltational shift of the pheromone structure arose within the genus Callosobruchus.

Semiochemistry of the Bruchidae species

“…It is distributed in the Afrotropical region, mainly in southern Africa (Giga and Smith, 1983). The presence of a female-produced sex attractant pheromone component was identified as (3S,6E)-7-ethyl-3,11dimethyl-6,10-dodecadienal (20) (Shimomura et al, 2010b). Besides, an additional electroantennographic active compound was detected without any characterization of its chemical properties.…”

Natural sesquiterpenoids

“…A new sesquiterpene 1 with biological activity has been isolated from hairy root cultures of Artemisia annua. 8-10 2,3-Dihydrohomofarnesal 2 has been identified as a component of the sex attractant pheromone of the female seed beetle Callosobruchus rhodesianus, 11 whilst the norsesquiterpene 3 may also be a possible component of this pheromone. 12 The sesquiterpene glycosides 4 and 5 have been found in extracts of Breynia fruticosa 13 and Gynostemma yixingense, 14 respectively.…”

Chiral methyl-branched pheromones

“…104), spiroacetals(105)(106)(107)(108)(109)(110)(111), and their related compounds(99 and 112) with methyl branches on the ring. Aer the identication of serricornin(72) with an acyclic structure from females of one death watch beetle species, cyclic anhydroserricornin (99) and dihydropyrans (100-102) were found in the same females as another sex pheromone component.…”