RESUMO
Let's swap: a scalable, atom-economic, enantio-, and diastereoselective synthetic route to trisubstituted γ-butyrolactones based on a Wagner-Meerwein-type dyotropic rearrangement of cis-ß-lactones is described. This methodology was applied in efficient and protecting-group-free formal syntheses and total syntheses of various xanthanolide natural products.
Assuntos
4-Butirolactona/química , Produtos Biológicos/síntese química , Lactonas/química , Sesquiterpenos/síntese química , Xanthium/química , Estrutura Molecular , EstereoisomerismoRESUMO
The 7-8 bicyclic ring system of micrandilactone A (1) with the required stereochemistry and functional groups was constructed by a Bu3Al-promoted Claisen rearrangement. Computational studies indicated that the exocyclic vinyl ether undergoes a [3,3] sigmatropic process via a chairlike transition state to afford exclusively the Z-double bond in the newly generated 8-membered ring with a high level of chirality transfer.