The early steps of spiroacetal biosynthesis in the fruit fly Bactrocera cacuminata (Solanum fly) have been investigated using a series of deuterium-labeled, oxygenated fatty acid-like compounds.
These potential spiroacetal precursors were administered to male flies, and their volatile emissions were analyzed for specific deuterium
incorporation by GC/MS.
This has allowed the order of early oxidative events in the biosynthetic
pathway to be determined.
Together with the already well-established later steps, the results of
these in vivo investigations have allowed essentially the complete
delineation of the spiroacetal biosynthetic pathway, beginning from
products of primary metabolism.
A fatty acid-equivalent undergoes a series of enzyme-mediated oxidations
leading to a trioxygenated fatty acid-like species that includes a
This moiety then undergoes enzyme-mediated oxidative carbon-carbon bond
cleavage as the key step, to generate the C9 unit of the final
This is the first time such an oxidative transformation has been
reported in insects.
A final hydroxylation step is followed by spontaneous spiro-cyclization.
This distinct pathway adds further to the complexity and diversity of biosynthetic pathways to spiroacetals.