RESUMO
The first enantioselective total synthesis of the structurally unique nortriterpenoid (-)-walsucochin B has been accomplished through the cationic polyolefin cyclization initiated by chiral epoxide. The core framework and the stereocenters in the natural product were all constructed in this step. A site-selective, late-stage free-radical halogenation and Seyferth-Gilbert homologation was adopted to install the acetylene moiety to synthesize the phenylacetylene. The absolute configuration of walsucochin B was confirmed through enantioselective total synthesis.
Assuntos
Produtos Biológicos/síntese química , Triterpenos/síntese química , Produtos Biológicos/química , Ciclização , Compostos de Epóxi/química , Radicais Livres , Estrutura Molecular , Estereoisomerismo , Triterpenos/químicaRESUMO
A concise asymmetric total synthesis of a fusarentin ether (1) with sequential biomimetic transformation to its analogues fusarentin 6,7-dimethyl ether (2), 7-O-demethylmonocerin (3), and (+)-monocerin (4) has been accomplished. The cis-fused furobenzopyranones of 7-O-demethylmonocerin (3) and (+)-monocerin (4) were efficiently constructed via an intramolecular nucleophilic trapping of a quinonemethide intermediate, which was obtained by benzylic oxidation of fusarentin 6-methyl ether (1) using hypervalent iodine reagent.