Investigations of Cascade Cyclizations of Terpenoid Polyalkenes via Radical Cations. A Biomimetic-type Synthesis of (±)-3-Hydroxy-spongian-16-one

Abstract

A short and efficient synthesis of the tetracyclic oxygenated diterpene analog of 8, i. e., of 3-hydroxy-spongian-16-one (7), has been achieved in only five steps via a cascade cyclization of the functionalized terpenoid polyalkene 4. Photoinduced electron transfer serves as the pivotal step for selectively creating a radical cation intermediate. Such polycyclizations are radical-driven upon regio- and stereoselective trapping of the radical cation by a nucleophile, such as water in the present case. The overall reaction sequence mimics the non-oxidative biosynthesis of terpenes.

Key words

photoinduced electron transfer - radical cation - biomimetic synthesis - photochemistry - 3-hydroxy-spongian-16-one - radical cyclization - natural products

References

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8

Xing, X.; Demuth, M. J. Am. Chem. Soc., accepted.

15

Goeller, F. Ph. D. Thesis; Max-Planck-Institut für Strahlenchemie/University of Essen: Germany, in progress.