A remarkably diverse suite of spiroacetals including a novel member of the rare, branched chain class has been identified in the glandular secretions of Bactrocera tryoni, the most destructive horticultural pest in Australia.

The volatile secretions of numerous species of Coleoptera (beetles), Hymenoptera (wasps, bees) and Diptera (true flies) contain complex blends of spiroacetals. In several species, a certain number of them appear to function as sex pheromones. The structure of insect-derived spiroacetals will be summarised and the techniques useful for their identification and the investigation of their biogenesis will be discussed. Progress in the study and delineation of likely biosynthetic pathways to these spiroacetals in Dipteran (Bactrocera) and Hymenopteran (Megarhyssa) species will be reviewed, and the validity of these pathways as a general paradigm for spiroacetal generation in the wider insect world will be assessed.

The major spiroacetal ((E,E)-1) of the pestiferous fruit flies, Bactrocera tryoni and Bactrocera cucumis, is biosynthesised from fatty acids by distinguishable pathways which utilise modified beta-oxidation and C-H hydroxylation, generating a putative ketodiol which cyclises.

A novel spiroacetal, (2S,6R,8S)-2-methyl-8-ethyl-1,7-dioxaspiro[5.6]dodecane (1), has been identified from the volatile secretions of female B. tryoni by mass spectral analysis and synthesis of an authentic, enantioenriched sample.

In pursuit of a more environmentally benign method of controlling the highly pestiferous Queensland fruit fly, Bactrocera tryoni, the biosynthesis of the minor components in the suite of spiroacetals released by females has been investigated. This follows on the biosynthetic definition of the pathway to the major component, (E,E)-1. The origins of the C(12) and C(13) spiroacetals (E,E)-2 and (E,E)-3, respectively, have been investigated by the administration of over 30 deuterated potential precursors. Analysis of the relative incorporation levels and identification of some of the exceptionally minor spiroacetals that were biosynthesised established that B. tryoni processes fatty acids to 2,6-dioxygenated precursors by a modified β-oxidation pathway, with a suite of putative cytochromes P450 employed in the crucial oxidative steps, prior to cyclisation of the proposed ketodiol.