Multiple chirality transfers in the enantioselective synthesis of 11-O-debenzoyltashironin. Chiroptical analysis of the key cascade.

The mechanism of the cascade oxidative dearomatization-transannular Diels Alder was investigated in the context of an asymmetric route to (-)-11-O-debenzoyltashironin. Although the oxidative dearomatization provides two acetal intermediates, the transannular Diels-Alder proceeds spontaneously from only one of the acetal isomers. Access to enantioenriched tetracyclic adduct was gained through the use of optically active allene.