The use of dipolar cycloaddition chemistry for the synthesis of numerous fused heterocyclic rings will be explored. The scope and mechanism of the ring contraction of isoxazolidines will be studied. The fluoride induced desilylation as a method of generating azomethine ylides will be investigated. A program dealing with the free radical induced cyclization of thioalkenylamines is also outlined. The development of general and synthetic routes leading to the synthesis of important biologically active compounds via the chemistry of alpha-aminonitriles will also be carried out. Many of the substances to be synthesized are expected to show interesting malignant-growth inhibiting properties and will be tested at the National Cancer Chemotherapy Service Center.