The first chapter of this thesis describes the stereocontrolled synthesis of the stereoisomers of 5-n-butyltetrahydrofuro-[3,2-b]furan-2(3H)-one and 5-n-hexyltetrahydrofuro-[ 3,2-b]furan-2(3H)-one, which had been identified in the Hagen's gland extracts of some braconid wasps. Jacobsen's Hydrolytic Kinetic Resolution (HKR) was utilised, along with a one pot, palladium catalysed hydroxycyclisation-carbonylation-lactonisation reaction that delivered the bicyclic lactones in an efficient manner. Enantioselective gas chromatography of the synthesized compounds, ensured that reliable values were obtained for the optical rotations. This methodology was then apphed to the synthesis of a tetrahydrofuro- [3,2-b]furan-2(3H)-one system that contained a p-bromobenzyl substituent, with the aim of
producing a compound suitable for X-ray structural analysis.
The second chapter describes the synthesis of stereoisomers of 2,3,8-trimethyl-1,7- dioxaspiro[5.5]undecane, utilising several approaches, including hydroxymercuration-cyclisation of an appropriate dienone; asymmetric dihydroxylation-cyclisation of a dienone; and a completely stereocontrolled, hydrazone based synthesis. The synthesised 2,3,8-trimethyl-1,7-dioxaspiro[5.5]undecane was then appraised as a component of the dorsal abdominal glandular extracts of the native aposematic shield bug, Cantao parentum.
The third chapter describes the isolation of bistramide A, a spiroacetal containing marine natural product that holds much promise in the area of cell signaling research. The NMR analysis of bistramide A was suggestive of the relative stereochemistry of the spiroacetal ring system. This stereochemistry was confirmed by the synthesis of a suitable
sub-fragment and comparisons with the natural sample. The stereochemistry found in bistramide A must also apply to the other members of the bistramide series of marine metabolites.
The final chapter of this thesis details studies into the biosynthesis of spiroacetal containing pheromones in two species of Suit fly, Bactrocera cucumis and Bactrocera cacuminata. Stereochemically defined, deuterated precursors were synthesized and administered to the fruit flies in order to elucidate the likely biosynthetic pathway leading to spiroacetal formation. The feeding experiments were performed under an atmosphere containing [18O2]-dioxygen, and the results strongly suggested that a cytochrome P450 was involved. Information was also gained about the stereochemistry of the naturally occurring precursors, and about the possibility of multiple precursor compounds, which could be
preferentially processed by the fruit flies.