Behavioral activity of stereoisomers and a new component of the contact sex pheromone of female German cockroach, Blattella germanica.

(3S,11S)-3,11-Dimethylnonacosan-2-one is a major component of the courtship stimulating, contact sex pheromone of the female German cockroach. Although the four synthetic stereoisomers of this compound have been tested in behavioral assays, their relative activity remains unresolved. Using isolated male antennae dosed with synthetic test compounds to assay male behavior, we found that at high doses all four stereoisomers elicited responses from 100% of the males. However, at physiologically relevant doses similar to those found on the female antenna, the (3S,11S)-isomer was the least effective of the four stereoisomers at eliciting courtship responses in males. This is the first example of a natural stereoisomer having less bioactivity than related stereoisomers that do not occur naturally. Another component of the sex pheromone blend, 3,11-dimethylheptacosan-2-one, was previously purified from the female's epicuticule and behaviorally assayed, but its activity was not confirmed through synthesis. We now confirm that synthetic (3S,11S)-3,11-dimethylheptacosan-2-one elicits behavioral responses, but less so than its C29 homolog.