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Free keywords:
cross coupling; Kocienski olefination; macrocyclization; marine natural products; polyenes
Abstract:
The assigned structure of the dinoflagellate-derived toxin belizentrin was prepared by total
synthesis in form of the corresponding methyl ester for stability reasons. The successful route features an unusual solution for the preparation of a recalcitrant ylid on a C-glycosidic segment; moreover, it involves an asymmetric hetero-Diels/Alder reaction en route to the tertiary hemiacetal substructure, a
Negishi cross coupling of two elaborate building blocks, and a macrocyclization based on an intramolecular aminolysis of a spirolactone. A modified Kocienski olefination ultimately allowed the polyol side chain to be attached to the macrocycle, although this transformation faced the exceptional base-sensitivity of this polyunsaturated target compound.
