Konstitution von Fusigen und dessen Abbau zu Δ2-Anhydromevalonsäurelaction.

Alkaline degradation of fusigen, a sideramine from fungi, yields the known monohydroxamic acid fusarinine. L-Ornithine and cis-5-hydroxy-3-methylpentenoic-2-acid occur in fusigen in equal amounts, and ornithine is the only amino acid. Amino group(s) with pK 7,1, but no free carboxyl group can be found in fusigen. The calculated equivalent weight is 280, which again points to fusarinine as a structural subunit. By acetylation of fusigen three products are obtained, which can be separated by electrophoresis or chromatography. The titration data of the partially acetylated fusigen and the molecular weight estimation by vapour pressure osmometry of the desferriform of the fully acetylated fusigen show that fusigen is a trimeric fusarinine. These data together with those obtained from IR- and NMR-absorption spectra lead to the proposed structure: three fusarinine molecules are esterified head-to-tail to build a 36-membered ring. The quantitative estimation of all hydroxamic acids in the culture fluid of Fusarium cubense from the 2nd to the 9th day of fermentation and structural studies on some of these compounds revealed the spontaneous degradation of fusigen by ring opening and sequential split-off of fusarinine units. An analogous degradation pathway starts from N-acetyl-fusigen. The Δ2-anhydromevalonic lactone, found in the cultures of several fungi, seems to stem from the degradation of fusarinine. The total yield of Δ2-anhydromevalonic lactone can be increased severalfold by treatment of the culture fluid with hydrochloric acid prior to extraction. [ABSTRACT FROM AUTHOR]