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  • 1
    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.
    Type of Medium: Electronic Resource
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  • 2
    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.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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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.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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.
    Additional Material: 1 Tab.
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  • 5
    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.
    Type of Medium: Electronic Resource
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  • 6
    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.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 835-843 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Isolation, 13C NMR Spectra, and Biosynthesis of Resistomycin and Resistoflavin from Streptomyces griseoflavus B 71 (Actinomycetales)From the mycelium of Steptomyces griseoflavus B 71 (Actinomycetales) resistomycin (1), resistoflavin (2), and 2-pyrrolecarboxylic acid (3) were isolated. 13C NMR spectra of 1 and 2 were recorded and assigned using long-range C,H coupling and H/D exchange. Feeding experiments with [1-13C]- and [1,2-13C]-acetate confirm biosynthesis from a decaketide precursor 4a folded in an S-shaped loop.
    Notes: Aus dem Mycel von Streptomyces griseoflavus B 71 (Actinomycetales) konnten Resistomycin (1), Resistoflavin (2) und 2-Pyrrolcarbonsäure (3) isoliert werden. Von 1 und 2 wurden die 13C-NMR-Spektren aufgenommen und mit Hilfe weitreichender C,H-Kopplungen und H/D-Austausch interpretiert. Nach Fütterungsexperimenten mit [1-13C]- und [1,2-13C]-Acetat geht 1 aus einem S-förmig gefalteten Decaketid 4a hervor.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Antibiotics from gliding Bacteria, XVII. - Myxopyronin A and B - Two Novel Antibiotics from Myxococcus fulvus Strain Mx f50From the gliding bacterium Myxococcus fulvus strain Mx f50 two antibiotics, named myxopyronin A and B, have been isolated and shown to possess the structures 9a and 9b. The two new compounds are 3-acyl-4-hydroxy-α-pyrones with an N-alkenylcarbamate function uncommon to natural products.
    Notes: Aus dem Kulturüberstand des Gleitenden Bakteriums Myxococcus fulvus Stamm Mx f50 (Myxobacterales) wurden zwei Myxopyronin A und B genannte Antibiotika isoliert und konstitutionell aufgeklärt. Es handelt sich um die Verbindungen 9a, b mit einer 3-Acyl-4-hydroxy-α-pyron-Struktur und einer für Naturstoffe ungewöhnlichen N-Alkenyl-Carbamat-Funktion.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 78-84 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Antibiotics from Gliding Bacteria, XVIII.  -  The Absolute Configuration of Myxalamide A and BThe absolute configuration of myxalamide A (1) and B (2) was deduced from the ozonolysis products of myxalamide A (1) and di-O-acetylmyxalamide B (5). The R configuration was determined for C-12 and C-13 from X-ray analysis of p-bromophenacyl 3-acetoxy-2-methyl-4-oxopentanoate (11). The S configuration of C-1′ was derived by comparison of synthetic O-acetyl-N-pyruvoyl-L-alaninol (12) with the identical degradation product. For the additional chiral center C-16 in myxalamide A (1) S configuration follows from degradation to (S)-2-methylbutyric acid (17).
    Notes: Die absolute Konfiguration von Myxalamid A (1) und B (2) wurde aus den Ozonolyseprodukten von Myxalamid A (1) und Di-O-acetylmyxalamid B (5) abgeleitet. Mit einer Röntgenstrukturanalyse des 3-Acetoxy-2-methyl-4-oxopentansäure-p-bromphenacylesters (11) wurde die R-Konfiguration für C-12 und C-13 bestimmt. Die S-Konfiguration von C-1′ wurde durch Vergleich von synthetischem O-Acetyl-N-pyruvoyl-L-alaninol (12) mit dem identischen Abbauprodukt ermittelt. Aus dem Abbau zu (S)-2-Methylbuttersäure (17) folgt S-Konfiguration für das zusätzliche Chiralitätszentrum C-16 im Myxalamid A (1).
    Additional Material: 1 Ill.
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  • 10
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Antibiotics from Gliding Bacteria, XXIII.  -  Stigmatellin A and B  -  Two Novel Antibiotics from Stigmatella Aurantiaca (Myxobacterales)From the cells of the gliding bacterium Stigmatella aurantiaca strain Sg a15 two novel antibiotics named stigmatellin A and B were isolated as a mixture in addition to the known myxalamides. The structure elucidation of the crystalline main component A (7a), using spectroscopic methods, degradation, and chemical transformations revealed the structure of an 8-hydroxy-5,7-dimethoxychromone system with a modified long-chain alkyl substituent in position 2. A simple synthesis for chromones with this substitution pattern not yet known also from natural products was developed.
    Notes: Aus den Zellen des Gleitenden Bakteriums Stigmatella aurantiaca Stamm Sg a15 (Myxobacterales) wurden neben den bekannten Myxalamiden zwei neue, Stigmatellin A und B (7a, b) genannte Antibiotika als Gemisch isoliert. Die Strukturaufklärung der kristallinen Hauptkomponente A (7a) mit Hilfe spektroskopischer Methoden, Abbau und Derivatisierung ergab ein 8-Hydroxy-5,7-dimethoxychromon-System mit einem langkettigen modifizierten Alkylrest in 2-Stellung. Eine einfache Synthese für Chromone mit diesem auch in der Natur bisher nicht bekannten Substitutionsmuster wurde ausgearbeitet.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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