The objective of the proposed work is the development of concise methodology for the stereocontrolled oxidation of enolates to alpha-hydroxy carbonyl compounds (RR'C(OH)C(O)Z) having high optical purity with predictable stereochemistry; the ultimate goal being the reagent-controlled asymmetric oxidation of prochiral enolates. The alpha-hydroxy carbonyl array is a common feature of many biologically important molecules that are ubiquitous in nature. Compounds having this moiety are also important intermediaries in the enantioselective synthesis of natural products such as sugars, antitumor agents, antibiotics and pheromones. These goals will be achieved by exploring the asymmetric oxidation of prochiral, tetra-substituted, acyclic and cyclic enolates (metalloenamines) using the readily available, optically pure (camphorylsulfonyl)oxaziridines 1/2 and diastereomerically pure 2-sulfamyloxaziridines 3. Double asymmetric induction, the asymmetric oxidation of chiral enolates, will also be explored as a route to optically active alpha-hydroxy carbonyl compounds. Metal-assisted asymmetric oxidations using (camphorylsulfonyl)oxaziridines 1/2 and 2- sulfamyloxaziridines 3 having metal chelating functional groups are anticipated to give alpha-hydroxy carbonyl compounds in high optical purity. The influence of counterion, solvent, enolate geometry and structure on the stereoselectivity of the oxidations will be determined. This information will be used to elucidate the origins of the asymmetric induction, to provide new information on the solution structure of enolates and to develop transition state models. This asymmetric enolate oxidation methodology will be applied to the enantioselective syntheses of (-)- eucomol and (+)d-demethoxydaunomycinone. The latter compound is a potent antitumor agent. The feasibility of reagent-controlled asymmetric oxidation of prochiral enolates to alpha-hydroxy carbonyl compounds in high optical purity using optically active 2-sulfonyloxaziridines has been demonstrated in preliminary studies.
