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Biomedical subjects

A Zeeck

Publications and source records attributed to A Zeeck.

At least 73 records · Page 4Linked to original sources
PubMed1990

Secondary metabolites by chemical screening: II. Amycins A and B two novel niphimycin analogs isolated from a high producer strain of elaiophylin and nigericin.

Two novel natural niphimycin analogs, amycins A (5) and B (3) were isolated from the culture broth of the Streptomyces sp. DSM 3816 by chemical screening methods. In addition this strain produces the antibiotics niphimycin (4), elaiophylin (2) and nigericin (1). Fermentation, isolation, structure elucidation and biological activity of the amycins are described.

Anti-Bacterial Agents↗
PubMed1990

Derivatives of saquayamycins A and B. Regio- and diastereoselective addition of alcohols to the L-aculose moiety.

In continuation of our structure-activity investigations on angucycline antibiotics we prepared derivatives of saquayamycins A (1) and B (4) by regio- and diastereoselective nucleophilic addition of different alcohols to the L-aculose moiety. Reversible protection of the 4'-hydroxy group in 1 by silylation allowed a derivatization at both L-aculose moieties without cyclization towards cinerulose B. The in vitro cytotoxic activity remained almost unchanged after variation at the L-aculose moieties whereas a change in the aglycone structure led to a total loss of the biological activity.

Alcohols↗
PubMed1989

Identification of oestrogen metabolites in human urine by capillary gas chromatography and mass spectrometry.

Oestrogen metabolites from the urine of males and pregnant and non-pregnant females were enriched by a procedure involving column chromatography on adsorber resins, gels and ion exchangers, enzymatic solvolysis and extraction, thereby separating the oestrogens from most of the interfering material. After derivatization of the oestrogens as their trimethylsilyl ethers profiles were measured with a fused silica column and a flame ionization detector by gas chromatography. Using a combination of capillary gas chromatography and mass spectrometry approximately 50 oestrogen metabolites were detected in the human urine of males and females, of which 19 were unknown urine compounds. Not all could be identified definitely owing to the lack of reference material. Mass spectra of trimethylsilylated oestrogens with functional groups at position 11 (11-dehydroestradiol, 11-dehydroestrone and 11 beta-hydroxyestrone) were discussed in their common and discernible fragmentations.

Chromatography, Gas↗
PubMed1989

Urdamycins, new angucycline antibiotics from Streptomyces fradiae. V. Derivatives of urdamycin A.

Derivatives of the angucycline urdamycin A (1) were prepared in order to study structure-activity relationships in this group of antitumor antibiotics. Derivatives of 1 formed by methanolysis, O-acylation, hydrogenation and treatment with diazomethane were isolated and characterized by their spectroscopic data. Urdamycin G (20) was isolated from Streptomyces fradiae by shortening the fermentation time. The different glycosidation pattern of the aglycone 14 did not lead to significant differences in the biological activity. O-Acylation was shown to enhance the in vitro activity of 1 against stem cells of murine L1210 leukemia depending on the lipophilicity of the molecules. The importance of the 5,6-double bond of 1 with regard to the antitumor activities is discussed.

Acetylation↗
PubMed1989

Viriplanin A, a new anthracycline antibiotic of the nogalamycin group. II. The structure of a novel hydroxyamino sugar from reduced viriplanin A.

Methyl 2,3,6-trideoxy-3-hydroxyamino-3-C-methyl-alpha-D-ribo-hexopyranoside+ ++ (2) and the corresponding amino sugar (4) were isolated from reduced viriplanin A by acidic methanolysis and esterified to the di-p-bromobenzoates (3 and 5), respectively. The absolute configuration of crystalline 3 was determined by X-ray analysis to be alpha-D. This result could be confirmed by oxidation of 2 to methyl alpha-D-decilonitroside (6) and from the CD spectra of 3 and 5. Thus, the nitrogen-containing sugars of viriplanin A and probably those of decilorubicin and arugomycin belong to the D-series.

Anthracyclines↗
PubMed1988

Metabolic products of microorganisms. 249. Tetracenomycins B3 and D3, key intermediates of the elloramycin and tetracenomycin C biosynthesis.

Tetracenomycins B3 and D3, besides tetracenomycin D (D1), were produced by a blocked mutant of the elloramycin producer Streptomyces olivaceus TU 2353. The compounds were isolated as red powders, and their structures were elucidated by comparing their physicochemical data with those of the known tetracenomycins A2, B1, B2, D and E. Tetracenomycin B3 (2), the main compound, and tetracenomycin D (3) were antibiotically inactive against Gram-positive and Gram-negative bacteria, whereas tetracenomycin D3 (1) showed a moderate activity against Bacillus subtilis and Arthrobacter aurescens. Tetracenomycin B3 (2) is the key intermediate where the biosynthesis of the elloramycins branches off from the line leading to tetracenomycin C (5) as the final product of the tetracenomycin biosynthesis branch.

Anthraquinones↗
PubMed1988

Metabolic products of microorganisms. 244. Colabomycins, new antibiotics of the manumycin group from Streptomyces griseoflavus. I. Isolation, characterization and biological properties.

The yellow colabomycins A to C, three new antibiotics of the manumycin group produced by Streptomyces griseoflavus (strain Tü 2880), were detected by chemical screening. They were isolated from mycelium extracts by column chromatography on various adsorbents, followed by preparative reversed phase HPLC. The main compound, colabomycin A (1), was characterized and shown to be chiefly biologically active against Gram-positive bacteria and stem cells of murine L1210 leukemia.

Alkenes↗
PubMed1988

Metabolic products of microorganisms. 245. Colabomycins, new antibiotics of the manumycin group from Streptomyces griseoflavus. II. Structure of colabomycin A.

The structure of colabomycin A (1) was elucidated by a detailed spectroscopic analysis. Two-dimensional NMR spectroscopy experiments provided assignments of the proton and carbon resonances of the tetraene carboxamide chains occurring in 1. The configurations of eight out of nine double bonds were determined by analysis of their coupling constants. The absolute configurations of C-4 (4S), C-5 (5R) and C-6 (6S) were established from the CD spectra of the parent compound and of 2-(6-oxo-2,4-hexadienoylamino)-5,6-epoxy-1,4-benzoquinone (2), which was obtained from 1 by mild chromic acid oxidation.

Alkenes↗
PubMed1988

Metabolic products of microorganisms. 243. Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger.

Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger sp. griseofuscus (strain Tü 2557), was detected in a selective screening against Mucor hiemalis (Tü 179/180). The amino acid side chain of 1 can be seen as L-ornithine, whose gamma-nitrogen atom is part of a pyridazine ring building a quaternary ammonium system. The structure of 1 was established by spectroscopic analysis of the parent compound and degradation products. The occurrence of a pyridazine ring in microbial secondary metabolites is unique.

Antifungal Agents↗
PubMed1987

Metabolic products of microorganisms. 239. Bacimethrin isolated from Streptomyces albus identification, derivatives, synthesis and biological properties.

Bacimethrin (1), known as a thiamine antagonist produced by Bacillus megatherium, was isolated from Streptomyces albus and has been further characterized by NMR spectra and acetylation. A new easy three step synthesis for 1 is described. The biological activity of 1, and its mode of action were discussed. There are indications that bacimethrin inhibits the phosphorylation of 4-amino-5-hydroxymethyl-2-methylpyrimidine (Pyr-OH) during thiamine biosynthesis.

Acetylation↗
PubMed1987

The structure of manumycin. I. Characterization, structure elucidation and biological activity.

Manumycin (1), produced by Streptomyces parvulus (strain Tü 64), was isolated from the mycelium by extraction with acetone and could easily be purified chromatographically. Chemical degradation of 1 (C31H38N2O7) gave 2-acetamino-3-hydroxycyclopent-2-enone (2) by acetolysis, 2,4,6-trimethyl-2,4-decadienoic acid (3) by alkaline hydrolysis, and 2-(2,4,6-trimethyl-2,4-decadienoylamino)-5,6-epoxy-1,4-benzoquinon e (5) by chromic acid oxidation. In connection with a detailed spectroscopic analysis, the structure of 1 could be elucidated and the (E)-configuration of the double bonds in the triene and diene chain was established. Manumycin exhibits biological activity against Gram-positive bacteria and fungi and furthermore, an inhibition of the developmental processes of some insects.

Alkenes↗
PubMed1987

The structure of manumycin. II. Derivatives.

Derivatives of manumycin (1) were obtained by acetylation and reduction, respectively, and characterized by their spectroscopic data. Structure-activity relationships of the antibiotic were discussed.

Acetylation↗
PubMed1987

The structure of manumycin. III. Absolute configuration and conformational studies.

Chromic acid oxidation of manumycin (1), an antibiotic produced by Streptomyces parvulus (strain Tü 64), led to the isolation of 2-(2-methyl-4-oxo-2-pentenoylamino)-5,6-epoxy-1,4-benzoquinone (3) and (-)-(R)-2-methylhexanoic acid (4). From the absolute configuration of 4, determined by comparing its optical rotation with published data, follows the absolute configuration at the center of chirality in the diene side chain of manumycin (1) to be (6'R). Based on the direct comparison of the CD spectra of the two chromic acid oxidation products 2 and 3 with those of the antibiotic G7063-2 (5) and (-)-terreic acid (6) the stereochemistry at C-5 and C-6 of 1 was determined as (5R, 6S). From the negative CD-couplet of manumycin (1) its stereochemistry at C-4 was assigned as (4R).

Alkenes↗
PubMed1987

Metabolic products of microorganisms. 240. Urdamycins, new angucycline antibiotics from Streptomyces fradiae. II. Structural studies of urdamycins B to F.

The structures of the angucycline antibiotics urdamycin B (5), E (2) and F (9) were established by comparing of their spectra with those of urdamycin A (1). The structures of urdamycins C and D, the largest compounds of this series, are still incomplete (10 and 11). The aglycones urdamycinone C, D and E can be liberated by methanolysis of the corresponding urdamycins. The liberation of urdamycinone B (6) requires an alcohol-free medium, to prevent its rearrangement to the naphthacenequinone 7 or 8. The urdamycins differ from other O-glycoside series in their variety of aglycones.

Aminoglycosides↗