Studies are proposed to execute a total synthesis of the potent platelet activating factor antagonists, the ginkgolides, including ginkgolide A, B, bilobalide, crinipellin A, paniculatine and lubimol. This will involve the investigation of diastereoselectivity in the photocycloadditions of enones containing two stereogenic centers on the tethering chain. A novel cyclobutyl carbinyl radical fragmentation-ring expansion sequence will also be investigated as a method for the synthesis of spirocarbocyclic ring systems. Intramolecular photocycloadditions on systems with removable tethers will be investigated as a means for controlling the regiochemical and stereochemical results of intermolecular photocycloadditions. The conjugate addition cyclization of zinc-copper homoenolates will be extended to larger rings and more functionally complex systems. Finally, a project directed toward the development of an auxiliary directed asymmetric [2+2] photocycloaddition on 2-carboalkoxycyclopent-2-en-l-ones will be initiated.