Synthetic and analytical studies of the ecological chemistry of insects and plants.

摘要

This thesis deals with three separate studies in chemical ecology. The first two chapters describe the synthesis and biological evaluation of a novel family of macrocyclic alkaloids which were recently isolated from the ladybird beetle Subcoccinella 24-punctata. Key steps in the synthesis include (1) the opening of a chiral aziridine using the anion of THP-protected propargyl alcohol, (2) the selective deprotection of an allyl ester in the presence of a second ester function, and (3) a Mukaiyama macrolactonization The synthetic material is shown to act as a potent feeding deterrent to the predacious ladybird beetle Harmonia spp.; The third chapter involves the identification and quantification of the pigments responsible for the delineation of floral nectar guides in the St. John's Wort species Hypericum calycinum. The major pigments responsible for the patterns are shown to be dearomatized isoprenylated phloroglucinols. The dearomatized isoprenylated phloroglucinols are found to be present in very high concentrations in the anthers and ovary walls of the flowers, suggesting a second, defensive role. Such a role is supported by bioassays, which were carried out using the larvae of Utethisa ornatrix .; The final chapter describes the quantification of cantharidin in samples of field-caught beetles from two species. A general protocol is developed for the analysis of sub-nanogram amounts of cantharidin using gas chromatograph-coupled mass spectrometry.