A very rapid stereocontrolled entry to highly functionalized [5-8-5] ring systems using the Saegusa reaction

[GRAPHICS] A highly functionalized dicyclopenta[a,d]cyclooctanone product, representing the basic [5-8-5] skeleton found in natural products such as the ophiobolins and fusicoccins, was prepared in only four synthetic steps from a readily available bridged ketone. The highly stereoselective sequence involves use of the Saegusa ring expansion protocol to effect initial ring expansion-cyclization and a subsequent radical cyclization using TolSO(2)SePh.