Total Synthesis of Apoptolidin: Part 2. Coupling of Key Building Blocks and Completion of the Synthesis We thank Dr. C. Khosla and Dr. Y. Hayakawa for generous gifts of apoptolidin, and Dr. D. H. Huang and Dr. G. Siuzdak for NMR spectroscopic and mass spectrometric assistance, respectively. This work was financially supported by the National Institutes of Health (USA), the Skaggs Institute for Chemical Biology, American Biosciences, a predoctoral fellowship from Boehringer Ingelheim (to Y.L.), a postdoctoral fellowship the George Hewitt Foundation (to K.C.F.), and grants from Abbott Laboratories, ArrayBiopharma, Bayer, Boehringer Ingelheim, DuPont, Glaxo, Hoffmann-LaRoche, Merck, Novartis, Pfizer, and Schering Plough.