Modellreaktionen zur Biosynthese von Verbindungen der Damascon-Reihe und ihre präparative Anwendung

We report a new general synthesis of damascones. In the presence of acids, 7, 8-dehydro-β-ionole ( 10 ) or the related diols 11 are converted into a mixture of β-damascone ( 2 ) and the 7, 8-dehydrotheaspiranes ( 19 ). In the same way the 6-hydroxy-7, 8-dehydro-α-ionoles 12 are transformed into a mixture of β-damascenone ( 3 ) and the 8-oxatheaspiranes ( 20 ). The reaction Provides access to damascone derivatives 4 – 7 which have been found in nature. These synthetic experiments lend support to our hypotheses concerning the biogenesis of damascones from suitable carotenoids or their metabolites.     

Zur Biosynthese der Rubratoxine

In order to check the hypothesis that rubratoxin B ( 2 ), a C₂₆-metabolite, is formed biogenetically by head-to-tail coupling of two identical C₁₃-precursors derived from decanoic acid and oxaloacetic acid, two labelled forms of the postulated C₁₃-intermediate 2-((E)-1'-octenyl)-3-[¹⁴C]methyl- and 2-((E)-1'-octenyl)-3-[¹³C]-methylmaleic anhydride ( 10 ), were synthesized. The labelled compounds 10 as well as a number of other ¹⁴C]- and [¹³C]-labelled potential precursors were administered to growing cultures of Penicillium rubrum STOLL . Significant incorporation rates of acetate (as intact units) and malonate were observed. Propionate was incorporated after decarboxylation. Succinate exhibited the highest rate of incorporation. The results are in agreement with the assumption that the C₁₀-chain is formed by the fatty acid pathway and the C₃-unit via the tricarboxylic acid cycle. After administration of 10 randomization of the label was observed. Thus the question whether compound 10 is a biogenetic intermediate remains unanswered.     

Zur Biosynthese der Gentisinsäure

Zusammenfassung Die Biosynthese der Gentisinsäure wurde mittels markierter Vorstufen in vier Arten höherer Pflanzen untersucht. Es konnte gezeigt werden, daß Gentisinsäure über die Zwischenstufen Zimtsäure, Benzoesäure und Salicylsäure gebildet wird. Die Hydroxylierung erfolgt hier erst auf der Stufe der Benzoesäuren, während andere Hydroxybenzoesäuren (z. B. 4-Hydroxybenzoesäure und Vanillinsäure) durch unmittelbaren Abbau aus den entsprechend substituierten Zimtsäuren entstehen.

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Biosynthesis of gentisic acid was investigated by the use of labelled precursors in four species of higher plants. We showed that gentisic acid is formedvia the intermediates cinnamic, benzoic, and salicylic acid. Thereby hydroxylation occurs at the benzoic acid level, whereas other hydroxybenzoic acids (e.g. 4-hydroxybenzoic and vanillic acid) originate by immediate degradation of correspondingly substituted cinnamic acids.

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Unserem verehrten Lehrer, Herrn Prof. Dr. Dr. h. c.F. Wessely, zum 70. Geburtstag in Dankbarkeit gewidmet.