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
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