Description: (Verbatim from the Applicant's Abstract) The continuing development of alkynyliodonium salt-mediated carbocyclization and heterocyclization reactions, and application of this chemistry to the total synthesis of therapeutically promising natural products, is planned. A concise synthesis of the potent antileukemic principle from Menispermaceae, pareitropone, will be initiated. In addition, a synthesis program directed toward the structurally novel VCAM-1 induction inhibitor halichlorine will commence. The discovery of new cascade cyclizations triggered by nucleophilic addition to alkynyliodonium salts bearing appropriately positioned unsaturated functionality will constitute a central thrust of the proposed research. These multi-step transformations will lead to efficient assembly of a variety of commonly encountered polycyclic ring systems, including diquinanes, precapnellanes, alpha-methylenecyclopentanones, cyclopentannelated benzofurans, and cyclopentannelated indoles. In a separate vein, the generation and productive carbocyclization of silyloxyalkylidene carbenes will be investigated. Promising advances in these developmental studies will be followed by application of the methodology toward the synthesis of cognate targets. Taken together, these studies will introduce new and concise techniques for preparing small polycyclic organic molecules of the type typically sought as pharmaceutical leads.