Martina Herrmann

Maracin and Maracen: New Types of Ethynyl Vinyl Ether andα-Chloro Divinyl Ether Antibiotics fromSorangium cellulosum with Specific Activity Against Mycobacteria

Like something originating from the chemistry laboratory rather than from Nature: However, the title compounds 1 and 2 are, in fact, synthesized by myxobacteria of the species Sorangium cellulosum according to the same assembly pattern from acetate and are excreted into the culture medium. Both compounds have remarkably good in vitro activity against the pathogen responsible for tuberculosis, Mycobacterium tuberculosis.

Sulfangolids, macrolide sulfate esters from Sorangium cellulosum.

Sulfangolids are the first sulfate ester containing secondary metabolites from myxobacteria. The metabolites 1-4 and the structurally related kulkenon (5) were isolated from different strains of the species Sorangium cellulosum. In the course of isolation all metabolites proved to be rather sensitive due to their conjugated double bond systems and the strong acidic nature of the sulfate ester in sulfangolids. The relative configuration of sulfangolid C (3) was assigned by extensive 1D and 2D NMR analysis and molecular modelling. In addition, the biosynthesis of 3 was studied by feeding experiments.

Chemical Modification of Thiangazole A in the Oxazole and Styryl Region

The partial synthesis of 54 derivatives of thiangazole A (1a), a new polythiazoline antibiotic from Polyangium spec. (myxobacteria), is described. Derivatives with chemical modification of the carboxamide group in the oxazole region were prepared either by N-alkylation to amides 5–14 or by methanolysis to ester 15, and its transformation products 16, 19, 20. Oxidation of the C-5 methyl group of 1a with molecular oxygen led to the hydroxymethyl derivative 21, and two by-products lacking the C-5 methyl group (22), or the entire oxazole ring (23). Key intermediate for analogues with modifications in the styryl region is the aldehyde 27, obtained by direct cleavage of the C-21/C-22 double bond. 27 was transformed into the oximes 37–42 and by Wittig reaction to (21Z)-thiangazole (43) and analogues 44–46 with proton and alkyl residues replacing phenyl. 21,22-Didehydrothiangazole (50) was synthesized in a multi-step reaction from 27 via the 20-alkinyl intermediate 49. The insecticidal activities and inhibition of the respiratory chain (complex I) by the thiangazole analogues were determined and compared with the natural product.