| Abstract: | 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. |
