New oxygenated himachalenes in male-specific odor of the Chinese windmill butterfly, Byasa alcinous alcinous

Abstract

Male adults of the Chinese windmill Byasa alcinous alcinous (Papilionidae) are well known to have a strong musk-like odor, in which two oxygenated himachalene compounds, together with six sesquiterpene hydrocarbons, were newly discovered. γ-Himachalen-4-yl acetate (1) was the predominant compound isolated from the solvent extract of the males. The structure of 1 was determined using MS and NMR, and its relative configuration was established as 1S^*,4R^*,6R^* by NOE analysis with the help of quantum mechanical computation. Interestingly, the amount of 1 in males increased until 7 days after eclosion, suggesting that this compound is involved in sexual maturation for mating. Another new compound was identified as γ-himachalen-4-ol (2) by comparison with the retention time and mass spectrum of the hydrolysate of 1. Since males of other papilionid species have general volatiles omnipresent in plants and insects, the presence of species-specific volatiles in males is characteristic of B. alcinous alcinous.

Keywords:

• adult butterfly
• Papilionidae
• Byasa alcinous alcinous
• male-specific volatiles
• γ-Himachalene derivatives
• simulation-aided conformational analysis

Acknowledgements

The NMR measurements at 600 MHz and the HR-GC-TOF-MS were carried out using a Jeol ECA NMR spectrometer and a Jeol JMS-T100GCV 4G mass spectrometer, respectively, at the Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University.

Disclosure statement

This study was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Sciences (JSPS) to H.O. [grant number 22780047].