(R,Z)-7,15-Hexadecadien-4-olide, sex pheromone of the yellowish elongate chafer, Heptophylla picea

An active component of the sex pheromone system of the yellowish elongate chafer, Heptophylla picea was identified by GG-EAD. Mass spectral data and hydrogenation revealed that the active compound was a hexadecadien-4-olide. It was not possible to determine the double bond positions by direct DMDS derivatization of the pheromone, but partial hydrogenation (diimide) followed by DMDS derivatization showed that the double bonds were located in positions 7 and 15. FTIR (tracer) of the pheromone corroborated the lactone structure (1772 cm^-1) and showed a band characteristic of a terminal double bond at 3073 cm^-1, and one of a double bond in the cis-configuration at 3002 cm^-1. Chiral resolution of the pheromone, after hydrogenation, demonstrated that the natural lactone had the (R)-stereochemistry. Synthetic (R,Z)-7,15-hexadecadien-4-olide, prepared from L-malic acid in 14 steps, was identical to the natural product in MS, IR, retention times and biological activity. This is the first fatty acid derivative compound found as a sex pheromone of a Melolonthinae species and as far as biosynthesis is concerned this is the most complex pheromone constituent of a scarab species.