[<sup>18</sup>O]-Oxygen Incorporation Reveals Novel Pathways in Spiroacetal Biosynthesis by <i>Bactrocera cacuminata</i> and <i>B. cucumis</i> FletcherMary T. WoodBarry J. M. BreretonIan StokJeanette E. J. De VossJames KitchingWilliam 2002 The origins of the oxygen atoms in 1,7-dioxaspiro[5.5]undecane (<b>1</b>) and hydroxyspiroacetal (<b>2</b>) from <i>Bactrocera cacuminata</i>, and in 2,8-dimethyl-1,7-dioxaspiro[5.5]undecane (<b>3</b>) and hydroxyspiroacetal (<b>4</b>) from <i>B. cucumis</i>, have been investigated by incorporation studies from both [<sup>18</sup>O<sub>2</sub>]-dioxygen and [<sup>18</sup>O]-water. Combined GC-MS examination and high-field NMR analysis have demonstrated that all oxygen atoms in <b>1</b> and <b>2</b> from <i>B. cacuminata</i> are dioxygen derived, but in contrast, the spiroacetals <b>3</b> and <b>4</b> from <i>B. cucumis </i>incorporate one ring oxygen from water and one ring oxygen (and the hydroxyl oxygen in <b>4</b>) from [<sup>18</sup>O<sub>2</sub>]-dioxygen. These results reveal not only the generality of monoxygenase mediation of spiroacetal formation in <i>Bactrocera</i> sp., but also an unexpected complexity in their biosynthesis. A general paradigm accommodating these and other observations is presented.