An Enantiospecific Synthesis of the Potent Immunosuppressant FR901483 Dr. G. Scheffler and H. Seike contributed equally to this work. We thank Dr. L. B. Pasternack and Dr. D. H. Huang for NMR spectroscopic assistance, and Dr. G. Siuzdak for mass spectrometric assistance. We also thank Dr. S. Takase and Dr. H. Setoi from the Fujisawa Pharmaceutical Co. for physical data for FR901483. This work was generously supported by The Skaggs Institute for Chemical Biology, a grant from the Merck Research Laboratories, a Beckman Young Investigator Award to E.J.S., and a predoctoral fellowship from the Heiwa Nakajima Foundation to H.S.