The specific aims of the research proposed are: (1) The development of an efficient method for the enantioconvergent production of an optically pure intermediate (a protected 4,5-dihydroxy-2-cyclopenten-1-one) of broad utility in the synthesis of a variety of biologically active oxygenated cyclopenanoids. (2) Optimization of the utilizaton of this intermediate in the development of a synthesis of the antitumor carbocyclic nucleoside, (-)-neplanocin A, by exploration of a number of synthetic pathways. (3) Utilization of the intermediate developed in (1) and the chemistry explored in (2) to synthesize a number of neplanocin A analogues (in which the base component has been altered) for screening as antitumor and/or antiviral agents. (4) Conversion of the intermediate noted in (1) into an optically pure form of "(-)-carbocyclic ribose" and conversion of this to the antibiotic (-)-aristeromycin. (5) Demonstration of the utility of the intermediate noted in (1) in the synthesis of an optically pure prostaglandin and other biologically interesting natural products. (6) Synthesis of simplified prostanoid targets which contain enone or latent enont functionality for screening in an effort to establish structure/activity relationships, particularly as DNA polymerase inhibitors, for compounds of this class as antineoplastic agents.