Sex pheromone of the scarab beetle Phyllophaga elenans and some intriguing minor components

Abstract

Three amino acid-derived compounds were identified in extracts from the pheromone glands of the scarab beetle Phyllophaga elenans, i.e., L-isoleucine methyl ester (LIME), N-formyl L-isoleucine methyl ester (For-LIME), and N-acetyl L-isoleucine methyl ester (Ac-LIME). The compounds were characterized from their spectral data (MS and IR), confirmed by synthesis, and their absolute configurations were assigned by gas chromatography with a chiral phase column. The amount of LIME in calling females was ca. 2 microg/gland, whereas only traces of For-LIME and Ac-LIME (0.005% of LIME) were detected in fresh extracts. Regardless of the storage temperature, the amounts of the minor constituents in the extracts increased overtime. Field tests showed that traps baited with For-LIME captured more beetles than control traps. Ac-LIME per se was not attractive, and it did not increase trap catches when combined with For-LIME. Traps baited with LIME caught ca. 150 beetles/trap/day, but catches did not increase with the addition of For-LIME and/or Ac-LIME in binary or tertiary blends.