A new methodology for the enantiospecific synthesis of taiwaniaquinoids, based on a thermal 6Ï electrocyclization, is reported. Under this procedure, 4a-methylhexahydrofluorene terpenoids bearing an A/B trans-configuration has been prepared for the first time. This methodology also makes it feasible to synthesize taiwaniaquinoids with an A/B cis-configuration and 4a-methyltetrahydrofluorene terpenoids. Accordingly, the first synthesis of (â)-taiwaniaquinone G, (â)-taiwaniaquinone H and (â)-dichroanone has been achieved.
The first route towards taiwaniaquinoid terpenes bearing an A/B trans-configuration has been developed through a sequence which includes a thermal 6Ï electrocyclization.