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  • 1
    ISSN: 0947-3440
    Keywords: Antibiotics ; Sorangium cellulosum ; Myxobacteria ; Antifungal agent ; Biosynthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The antifungal metabolite ratjadone (1) was isolated from the myxobacterium Sorangium cellulosum, strain So ce360. Production was achieved by fermentation in the presence of the adsorber resin XAD-16, extraction and separation by RP chromatography. The structure of 1 was determined by spectroscopic methods. It is characterized by a 4-hydroxytetrahydropyran and a 5,6-dihydropyran-2-one ring which are connected by an unsaturated C11 carbon chain. The polyketide origin of 1 was proven by feeding experiments with 13C-labeled precursors and NMR spectroscopic examinations.
    Additional Material: 4 Ill.
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  • 2
    ISSN: 0947-3440
    Keywords: Antibiotics ; Sorangium cellulosum ; Macrolides ; Mass spectrometry ; X-ray structure analysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two novel metabolites, sorangiolide A (1) and B (2), were isolated from the mother liquors and side fractions of the sorangicin A pilot-scale production. Their structures were elucidated by 2D-NMR spectroscopy and mass spectrometry as 18-membered macrolactones with a C11-carboxylic acid side chain. Sorangiolide B (2) differs from A (1) by an additional hydroxyl group at C-6 in the side chain. The absolute configuration of sorangiolide A (1) was established by X-ray structure analysis. The sorangiolides show a weak antibiotic activity against Gram-positive bacteria.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0947-3440
    Keywords: Antibiotics ; Polyketides ; Sorangium cellulosum ; RNA polymerase inhibitors ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three closely related new metabolites named ripostatins were isolated from the myxobacterium Sorangium cellulosum and their structures elucidated by spectroscopic methods. Two of them, ripostatin A (1a, b) and B (2a), are 14-membered macrolides with an acetic acid and a phenylalkyl side chain, whereas the third metabolite ripostatin C (3a) is an acyclic derivative of ripostatin A. By application of the method of Helmchen the absolute stereochemistry could be determined as (11R,13R) for ripostatin A, 11R,13S,15R for ripostatin B and 11S for ripostatin C. The polyketide origin of A was revealed by feeding experiments with 13C-labeled precursors demonstrating the incorporation of one molecule of phenylacetic acid derived from phenylalanine, one propionate unit, and ten acetate units.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3381-3392 
    ISSN: 1434-193X
    Keywords: Antibiotics ; Thiangazoles ; Polythiazolines ; Oxazoles ; Structure-activity relationships ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2046/1999/99007_s.pdf or from the author.
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  • 5
    ISSN: 1434-193X
    Keywords: Chondromycesspec. ; Myxobacteria ; Antibiotics ; Fungicides ; Structure elucidation ; Relative configuration ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Four novel antifungal and highly cytotoxic metabolites, the crocacins A-D (1-4), were isolated in our screening of the myxobacterial genus Chondromyces from strains of C. crocatus and C. pediculatus. Crocacin A, B, and D (1, 2, and 4) are unusual dipeptides of glycine and a 6-aminohexenoic or -hexadienoic acid, which is N-protected by a complex polyketide-derived acyl residue. The latter is a multiply substituted phenylundecatrienoic acid, which is found as its primary amide crocacin C (3). Based on 1H coupling constants, NOEs and MM+ calculations the relative configuration of the asymmetric centers and their preferred conformation are proposed for the crocacins.
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  • 6
    ISSN: 0947-3440
    Keywords: Antibiotics ; Soraphen ; Macrolide antibiotics ; Structure-activity relationship ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present paper describes the chemical modification of the antifungal macrolide soraphen A1α (1) by selective removal of oxygen substituents in the south-east ring segment. In the course of this investigation two key derivatives were prepared: 4-demethyl-5-O-(4-methoxybenzyl)-4-episoraphen (6) and 3,5-dideoxy-4-oxosoraphen (22). 6 served as precursor for 4-demethoxysoraphen (19) and 4-demethoxy-5-deoxysoraphen (20). 22 was used for the deoxygenation in positions C-3, C-4 and C-5 and for the synthesis of 3,5-didesoxysoraphen (24) as well as 4-demethoxy-3,5-dideoxysoraphen (27). The comparison of the antifungicidal activity of these derivatives showed that the OH group in position C-3 is essential for the biological activity of the soraphens.
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  • 7
    ISSN: 0947-3440
    Keywords: Antibiotics ; Soraphen ; Macrolide antibiotics ; Structure-activity relationship ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The partial synthesis of 11 analogues of soraphen A1α (1) is described. Reductive lactone ring cleavage, transformation into (17R,S)-soraphenic acid 10 and cyclization provided unnatural 17-epi-soraphen A1α (12). Removal of the phenyl-C-17 ring segment of 1 by cleavage of the lactone moiety and the C-16/C-17 bond gave the aldehyde 16 as central intermediate. After homologation of 16, introduction of a new C-17 substituent R or H, and cyclization of the lactone ring, the soraphen analogues butyl-, thienyl-, and tolylsoraphen 2b, d, e and 22b, d, e and the desphenylsoraphen 2a were obtained. The ring-contracted soraphen analogues norsoraphen 29 and 30 and desphenylnorsoraphen 31 were synthesized by introduction of a phenyl group or reduction of the intermediate aldehyde 23 followed by cyclization to the lactone. The biological activity of the soraphen analogues against Candida albicans was determined. Compared to the natural product, all analogues exhibit reduced activity. The activity of the analogues strongly depends upon the nature of the substituent R, the configuration at C-17, and the ring size.
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  • 8
    ISSN: 0947-3440
    Keywords: Antibiotics ; Sorangium cellulosum ; Macrolides ; Chivosazole ; Biosynthesis ; Natural products ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The myxobacterial metabolites chivosazole A (1) and its variants (2-6) were discovered in Sorangium cellulosum, strain So ce12, which simultaneously provides the broad spectrum antibiotic sorangicin as well as the sorangiolides and disorazoles. The antifungal and cytotoxic chivosazoles (1-6) are novel glycosides of 6-deoxyglucopyranose derivatives and an aglycon that includes an oxazole in its 31-membered macrolide ring. The aglycon itself, chivosazole F (7), was formed by strain So ce885 and showed similar activity antibiotic and cytotoxic.The biogenetic origin of the structural elements in chivosazole F (7) was studied by feeding experiments with [1-13C]-, [1,2-13C]acetate, [methyl-13C]methionine and [1-13C]serine. Accordingly, the aglycon 7 is a polyketide assembled by condensation of nine acetate units, one serine unit and a further seven acetate units. While C-1 of serine is part of the macrolide ring, the amido to hydroxyl part of the serine together with C-1 of the adjacent N-acetyl unit form the 1,3-oxazole ring. C- and O-methyl groups are derived from methionine.
    Additional Material: 3 Ill.
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