Laurendecumallene B (1), isolated from Laurencia decumbens Kützing, a marine red alga found off the coast of Weizhou Island in China, belongs to a class of bioactive metabolites known as halogenated C15-acetogenins. A synthetically alluring molecule, 1 contains a bromoallene moiety, an 8-membered cyclic ether ring and a total of eight stereocenters in a compact 15 carbon skeleton. Furthermore, the partial relative stereochemistry of 1 has been previously reported, but not the axial chirality of the bromoallene substituent and the stereochemistry of the C-13 Br, along with the absolute stereochemistry of the molecule. Herein, we present the first asymmetric total synthesis of ent-1, utilizing two BDSB-induced cyclizations, accomplishing the target in 21 linear steps. To date, there has only been one reported attempt at the total synthesis of 1. This work helps to provide a starting point for the subsequent derivatization and screening of potentially bioactive analogues of the halogenated nonterpenoid C15-acetogenins class of molecules.

Total synthesis of ent-laurendecumallene B

2019 Spring National Meeting

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