Total Synthesis and Proof of Stereochemistry of Natural and Unnatural Pinnaic Acids: A Remarkable Long-Range Stereochemical Effect in the Reduction of 17-Oxo Precursors of the Pinnaic Acids This work was supported by the National Institutes of Health (Grant Numbers: CA28824). Postdoctoral Fellowship support is gratefully acknowledged by M.W.C. (U.S. Army BCRP, DAMD17-98-1-8154). We thank Dr. George Sukenick of the MSKCC NMR Core Facility for NMR and mass spectral analyses. We would like to thank professor Nakanishi for his supportive interest in the project.