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Configuration determination, cytotoxicity, natural products, structure elucidation, total synthesis The escaping fish are illustrating the feeding deterrence property of aplysiol B. More information can be found in the Communication by Keisuke Nishikawa, Yoshiki Morimoto et al. GLO:BDBM/03jan22:asia202101276-toc-0001.jpg PHOTO (COLOR): . gl GLO:BDBM/03jan22:asia202101276-toc-0001.jpg PHOTO (COLOR): . gl Keywords: configuration determination; cytotoxicity; natural products; structure elucidation; total synthesis EN configuration determination cytotoxicity natural products structure elucidation total synthesis 1 1 1 01/05/22 20220103 NES 220103 B Total assignments of stereostructures b of marine cytotoxic bromotriterpenoids, aplysiol B (laurenmariannol) and saiyacenol A derived from a sea hare or red alga, have been accomplished through their asymmetric syntheses from the known epoxide to elucidate their ambiguous stereostructures. [Extracted from the article]

There are marine cytotoxic bromotriterpenoids, named the thyrsiferol family that are structurally characterized by some tetrahydropyran (THP) and tetrahydrofuran (THF) rings. The thyrsiferol family belongs to natural products that are often difficult to determine their stereostructures even by the current, highly advanced spectroscopic methods, especially in acyclic systems including stereogenic tetrasubstituted carbon centers. In such cases, it is effective to predict and synthesize the possible stereostructures. Herein, to elucidate ambiguous stereostructures and unassigned absolute configurations of aplysiol B, laurenmariannol, and saiyacenol A, members of the thyrsiferol family, we carried out their asymmetric chemical syntheses featuring 6‐exo and 5‐exo oxacyclizations of epoxy alcohol precursors and 6‐endo bromoetherification of a bishomoallylic alcohol. In this paper, we report total assignments of their stereostructures through their asymmetric chemical syntheses and also their preliminary cytotoxic activities against some tumor cells. These results could not have been achieved without depending on asymmetric total synthesis. [ABSTRACT FROM AUTHOR]