Inhibition of male response of drugstore beetles to stegobinone by its isomer.

Stegobinone, (2S, 3R, 1'R)-2,3,-dihy dro-2,3,5-trimethyl-6-(1'-methyl-2'-oxobutyl)-4H-pyran-4-one, the sex pheromone of drugstore beetles (Stegobium paniceum L.), elicited the pheromonal response from the males of the species in our bioassay system; however, the synthesized diastereomeric mixture of this compound was actually inactive to the males. Although the stegobinone isolated from the beetles of this species had significant activity, its enantiomeric [(±)-2S,3R,1'S-] and diatereomeric [(±)-2S,3S,1'RS-] isomers were inactive. Adding the (±)-2S,3R,1'S isomer to stegobinone significantly reduced the male response. Furthermore, the activity of Stegobinone vanished on keeping it at room temperature for two weeks. In such a stored stegobinone sample, the presence of 2S,3R,1'S isomer, the inhibitory component, was confirmed. This isomer might be produced by C-1' epimerization during storage.