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.
Connecting C19 Norditerpenoids to C20 Diterpenes: Total Syntheses of 6-Hydroxy-5,6-dehydrosugiol, 6-Hydroxysugiol, and Taiwaniaquinone H, and Formal Synthesis of Dichroanone
作者:Karl Gademann、Chandan Jana、Rosario Scopelliti
DOI:10.1055/s-0029-1218806
日期:——
involves a benzilic acid rearrangement followed by decarboxylation. On the basis of this approach, a total synthesis of (-)-taiwaniaquinone H and a formal synthesis of (-)-dichroanone have been achieved. terpenoids - biomimetic synthesis - biosynthesis - oxidations - stereoselective synthesis - total synthesis
Less carbon: Following a biogenetic proposal, the unusual 6‐5‐6 carbon skeleton of C19 taiwaniaquinoids was obtained by an intramolecular benzilic acid rearrangement from a C20 precursor. A protecting‐group‐free total synthesis then allowed for the preparation of (−)‐taiwaniaquinone H (see scheme).