RESUMO
The convergent synthesis of a fully elaborated C13-C27 fragment of madeirolide A has been achieved. The key features of the synthesis include the stereocontrolled construction of both the THF and THP rings via visible-light-induced iridium-catalyzed radical cyclization and the late-stage union of the two oxacyclic subunits through nickel-catalyzed decarboxylative cross-coupling.
RESUMO
Garsubellinâ A is a thirty-carbon meroterpenoid capable of enhancing the enzyme choline acetyltransferase whose decreased level is associated with the symptoms of Alzheimer's disease. Due to the potentially useful biological activity along with the novel molecular architecture, this plant metabolite has remained a popular synthetic target. Herein we report a full account of our synthetic investigations that have led to the enantioselective total synthesis of garsubellinâ A, establishing its absolute stereostructure. The protecting group-free, twelve-step synthetic route has enabled the syntheses of the natural (-)-garsubellinâ A and its unnatural (+)-antipode.
Assuntos
Doença de Alzheimer , Produtos Biológicos , Humanos , Estereoisomerismo , Terpenos/química , Colina O-Acetiltransferase/metabolismoRESUMO
Garsubellinâ A is a meroterpene capable of enhancing the enzyme choline acetyltransferase whose decreased level is believed to play a central role in the symptoms of Alzheimer's disease. Due to the potentially useful biological activity together with the novel bridged and fused cyclic molecular architecture, garsubellinâ A has garnered substantial synthetic interest, but its absolute stereostructure has been undetermined. We report here the first enantioselective total synthesis of (+)-garsubellinâ A. Our synthesis relies on stereoselective fashioning of a cyclohexanone framework and double conjugate addition of 1,2-ethanedithiol that promotes aldol cyclization to build the bicyclic [3.3.1] skeleton. The twelve-step, protecting group-free synthetic route has enabled the syntheses of both the natural (-)-garsubellinâ A and its unnatural (+)-antipode for biological evaluations.