A Rapid Total Synthesis of Spirotryprostatin B: Proof of Its Relative and Absolute Stereochemistry F.v.N. gratefully acknowledges the Alexander-von-Humboldt-Stiftung for a Feodor-Lynen fellowship that was kindly backed by Dr. R. Breslow as second host. This research was supported by the National Institutes of Health (Grant number HL 25848). We thank Dr. H. Osada (RIKEN) for providing us with spectra of the natural product. Furthermore we are grateful to Dr. D. Lichtblau from the Nakanishi laboratory for help with the CD spectra. We acknowledge the collaborative efforts of Ms. Maria Manzoni in these studies.