Structure Identification: |
Journal of Organic Chemistry, 1992 , 57 (17). | Cyclization reactions of the o-naphthoquinone diterpene aethiopinone. A revision of the structure of prionitin.[Reference: WebLink] | METHODS AND RESULTS:
The 4,5-seco-20(10→5)-abeo-abietane derivative aethiopinone (1), a natural o-naphthoquinone isolated from some Salvia species, was subjected to a series of acid-catalyzed reactions which yielded phenalene derivatives (2, 6, 9, and 11) and other cyclization products (3 and 10).
The 11-nor derivative 3 is formed by an intramolecular [4 + 2] cycloaddition reaction, and a mechanistic pathway for the formation of the phenalene derivatives 6 and 11 is also proposed. These transformations of aethiopinone (1) allowed the partial syntheses of the naturally occurring diterpenes salvipisone (8), salvilenone (9), and the racemic form of Prionitin (11), a rearranged abietane diterpenoid previously isolated from the root of Salvia prionitis, to which structure 12 had been attributed only on the basis of NMR spectroscopic studies.
CONCLUSIONS:
In the light of the results reported herein, including an X-ray analysis of compound 11, the structure 12 assigned to Prionitin must be changed to 11. |
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