Enantioselective Synthesis of (+)-Monobromophakellin and (+)-Phakellin: A Concise Phakellin Annulation Strategy Applicable to Palau'amine


  • We thank the NIH (GM52964) and the Welch Foundation for generous support. We also thank Dr. Joe Reibenspies for X-ray structural analysis, Francisco M. Torres for early studies in this project, and Prof. Justin Du Bois for helpful discussions.


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A unique oxidative cyclization of a tricycle bearing a guanidine aminal provides a concise route to the enantioselective synthesis of (+)-phakellin and (+)-monobromophakellin in nine and ten steps, respectively, starting from L-proline (see scheme). This sequence provides a simple annulation strategy applicable to the preparation of more complex members of this family of marine sponge-derived alkaloids including palau'amine.