RESUMO
The auto-oxidation of trans-1,2-disiloxybenzocyclobutene was found to be very efficient, giving endo-peroxide in quantitative yield. Each step of the mechanism of spin-forbidden addition of triplet oxygen O2((3)Σg) was studied by both EPR/spin trapping and theoretical studies.
RESUMO
The key is symmetry! A convergent synthetic approach of the highly cytotoxic natural product (-)-callystatinâ A was developed assembling three fragments through Julia-Kocienski olefination and Stille cross-coupling. The new strategy relies on a pivotal local symmetry of the target molecule. In this preliminary study, particular attention was devoted to facilitate the catalytic enantiocontrol of strategic stereogenic centers present in each of the fragments (see scheme).
Assuntos
Ácidos Graxos Insaturados/química , Alcenos/química , Animais , Callyspongia/química , Ácidos Graxos Insaturados/síntese química , EstereoisomerismoRESUMO
An efficient and rapid synthesis of the CDEF ring system of lactonamycinone is reported via a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disilyloxybenzocyclobutene and the appropriate γ-alkylidenebutenolide. The feasibility and the total chemoselectivity of the [4 + 2] cycloaddition for the construction of a spirolactone moiety via an intramolecular approach (IMDA) using both partners is also described demonstrating the versatility of the γ-alkylidenebutenolide building block.
Assuntos
Furanos/química , Quinonas/química , Alquilação , Ciclização , Indóis/síntese química , Estrutura Molecular , Naftoquinonas/síntese química , Espironolactona/química , EstereoisomerismoRESUMO
An efficient synthesis of deoxy-lambertellols was reported through a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disiloxybenzocyclobutenes and 2-methylprotoanemonine. Such transformation with δ-substituted γ-alkylidenebutenolides, to prepare new analogues of these tricyclic spirolactones, which would be very difficult to prepare by other ways, was also studied.