Strukturaufklärung der Phenalinolactone und Beiträge zur Biosynthese der Hexacyclinsäure (English shop)

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Chapter Abstract:

This dissertation dealt with biosynthetic studies as well as the isolation and structure elucidation of natural products from streptomycetes.

Within the framework of a collaborative project with the research group of Prof. Dr. H.-P. Fiedler (University of Tübingen), four compounds isolated from Streptomyces sp. Tü 6071 were obtained. Structure elucidation by means of spectroscopic methods (1D/2D NMR, HRESI-MS, IR, UV) revealed an unusual combination of a diterpenoid core skeleton with a trideoxy sugar, a pyrrolecarboxylic acid, and a novel gamma-lactone as substituents. NOESY experiments allowed the relative stereochemistry of the compounds, named phenalinolactone A–D, to be determined.

In the second part of the work, previous investigations into the biosynthesis of hexacyclinic acid were continued. Through feeding experiments with [1-13C, 18O2]-labelled precursor molecules, the biogenetic origin of almost all oxygen atoms could be established. On the basis of these results, a biosynthetic pathway was proposed and discussed with regard to other natural products, in particular FR182877. The involvement of a Diels–Alder reaction in the construction of the hexacyclic core skeleton of both hexacyclinic acid and the related compound FR182877 is likely. However, a further hetero-Diels–Alder reaction previously assumed in the literature to occur during the biosynthesis could be refuted.

Furthermore, 45 streptomycete strains isolated from three different soil samples were subjected to a chemical screening. Eight of the strains were investigated with respect to their secondary metabolite production. Isolation and structure elucidation of the constituents led to various compounds known from the literature.