Diterpenoide Drüsenfarbstoffe: Coleon L, ein neues Diosphenol aus Coleus somaliensis S. MOORE; Revision der Strukturen von Coleon H, I, I′ und K
✍ Scribed by Peter Rüedi; Conrad Hans Eugster
- Publisher
- John Wiley and Sons
- Year
- 1977
- Tongue
- German
- Weight
- 407 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Leaf‐gland Pigments: Coleon L, a New Diosphenolic Compound from Coleus somaliensis, S. MOORE; Revision of the Structures of Coleon H, I, I′ and K
From leaf‐glands of C. somaliensis a new, highly oxidized diosphenolic hydroquinone belonging to the abietane series was isolated in minute quantities. The new compound, coleon L (4c; C~24~H~30~O~10~), is very labile and transformed into its tautomer coleon K (5d) on standing in solution. ^1^H‐NMR. spectra of coleon L showed clearly that the points of attachment of the two acetoxy groups are at C(3) and C(16) contrary to the positions expected from our previously published structure 3 for coleon K. Application of a recently elaborated conversion of trans‐A/B‐6,7‐diketones of type 5 into the cis‐isomers 6 allowed to assign unambiguously the β‐configuration to the hydroxyl group at C(3) using pyridin induced solvent shifts. This confirmed structure 4c and 5d for coleon L and K, respectively. Based on similar reasons, the configuration at C(3) of coleon H, I and I′ had to be revised, the structures of these coleons being 4b, 5b and 5c, respectively.