Structural relationships between senfolomycins and paulomycins.

Senfolomycins A and B (Antimicrob. Agents Chemother.-1965: 828-831, 1966) are two antibacterial agents with physico-chemical and biological properties similar to those of paulomycin. Recent studies indicate that senfolomycin A (C29H36N2O16S, MW 700) has molecular composition and fast atom bombardment MS fragmentation pattern identical to those of paulomycin E. Extensive NMR work indicates that the two antibiotics, which have been separated by HPLC and TLC, differ only in the stereochemistry of the OCH3 group present in their respective sugar moieties. Indirect evident suggests that senfolomycin B is dihydrosenfolomycin A (C29H38N2O16S, MW 702) and in this respect it is related to paulomycin F. The proposed structures for senfolomycins A and B are discussed.

Chemical modification of steffimycin B.

Fifteen 3-substituted analogues of steffimycin B (1) have been synthesized and their activity against P388 murine leukemia has been determined. Three of these were substantially more active than the parent compound.

Paulomycin-related antibiotics: paldimycins and antibiotics 273a2. Isolation and characterization.

The isolation of paulomycins A and B from fermentations of Streptomyces paulus has been reported earlier [J. Antibiotics 35: 285-294, 1982]. Further work on the antibiotics produced by S. paulus revealed the production of two paulomycin-related compounds, antibiotics 273a1 and 273a2 which were isolated by procedures involving extractions and chromatography over buffered silica gel. Antibiotic 273a1 which has been named paldimycin, was found to be a mixture of two materials, paldimycins A and B (antibiotics 273a1 alpha, and 273a1 beta). Similarly, antibiotic 273a2 was found to consist of antibiotic 273a2 alpha and antibiotic 273a2 beta. Paldimycin and antibiotic 273a2, which are produced by addition of two or one molecules of N-acetyl-L-cysteine, respectively, to paulomycins A and B, are active vs. Gram-positive bacteria.

Enzymatic phosphorylation of macrolide antibiotics.

Five macrolide antibiotics (erythromycin A, 1; oleandomycin, 3a; tylosin, 4a; spiramycins, 5a; leucomycin A3, 6a) have been phosphorylated enzymatically using cell-free extracts derived from Streptomyces coelicolor UC 5240. The necessary cofactors and the rates of the conversion have been determined.

Structure--activity relationships of nogalamycin analogues.

Nogalamycin (1) has been modified by changes at C-10 and C-7 and in the dimethylamino group to prepare an extensive series of analogues. The chemistry involved in the modifications and structure--activity relationships among these nogalamycin analogues are discussed, as well as comparisons with previously reported compounds 1, 7-con-O-methylnogarol (2), and disnogamycin (11).

Primary amoebic meningoencephalitis.

The third case in the UK of primary amoebic meningoencephalitis is reported; it affected an 11-year-old girl. Six days before admission the girl had swum in a pool fed by hot spring water in which the causative agent Naegleria fowleri was found. Early treatment with amphotericin B would seem to offer the only hope of recovery in this almost uniformly fatal infection.

Microbial conversion of steffimycin and steffimycin B to 10-dihydrosteffimycin and 10-dihydrosteffimycin B.

It has been shown that steffimycin (1) and steffmycin B (2) are reduced at the C-10 carbonyl by Actinoplanes utahensis, UC-5885 and Chaetomium sp., UC-4634, respectively. Using cell-free extracts of the latter organism, the optimum conversion time, pH, and enzyme concentration have been determined for the conversion of 2 to 4. The biochemical conversion of 2 has been found to be TPNH linked.

Improved antitumor activity by modification of nogalamycin.

Nogalamycin, an antitumor antibiotic, has been converted to a series of analogs by removal of the carbomethoxy group at C-10 and replacement of the neutral sugar at C-7 by other groups. Removal of the carbomethoxy group to give disnogamycin (6) followed by acidic alcoholysis gave pairs of isomeric 7-alkoxy compounds differing in configuration at C-7. Treatment of 6 with trifluoroacetic acid followed by nucleophiles gave a series of analogs having substituents at C-7 with a configuration at C-7 opposite to that of nogalamycin. Among the analogs prepared, 7-con-O-methylnogarol (7) is a highly active antitumor agent.

Mammalian and microbial cell-free conversion of anthracycline antibiotics and analogs.

Cell-free preparations of Streptomyces nogalater and rat liver catalyze reduced pyridine nucleotide dependent conversion of nogalamycin to 7-deoxynogalarol and nogalose (Scheme 1). The mammalian process requires TPNH and has a specific activity of 85 nmoles of 7-deoxynogalarol formed per hour per mg of protein while the bacterial process prefers DPNH and has a specific activity of 5. The oxygen-sensitive conversions have pH optima of 7.5 (rat) and 9 (S. nogalater). Other anthracycline substrates converted to their 7-deoxyaglycones by both systems include nogamycin, 7(R)-O-methylnogarol, 7(R)-O-methylnogalarol, doxorubicin (Adriamycin), steffimycin, and steffimycin B.

Carbon-13 nuclear magnetic resonance assignments of pactamycin and related compounds.

All resonances observed in the 13C NMR spectrum of the antitumor antibiotic pactamycin and its degradation product pactamyçate have been assigned, employing off-resonance and specific proton decoupling as well as comparison with the 13C NMR spectra of the model compounds m-aminoacetophenone and ethyl 6-methylsalicylate.

Microbial metabolism of anthracycline antibiotics daunomycin and adriamycin.

It has been shown that the antitumor antibiotics daunomycin (1) and adriamycin (4) are metabolized by microorganisms in a fashion similar to their metabolism by mammalian cells. Both the fungus Mucor spinosus and its cell-free extracts reduce the 13-keto group of daunomycin to give daunomycinol (2) by a TPNH-dependent process. Cell-free extracts of Streptomyces steffisburgensis convert adriamycin and daunomycinol to their 7-deoxyaglycones (5) and (3) by DPNH-linked reductive glycosidic cleavage. Cell-free extracts of the latter organism convert 7-deoxyadriamycinone (5) to 7-deoxyadriamycinol aglycone (6) by TPNH-linked 13-keto reduction.

Detection and assay of antitumor antibiotics.

Cell culture techniques and antimicrobial systems can be used as detection systems for new antibiotic structures. Antimicrobial systems by virtue of their speed, economy, ease of use, and adaptation to chromatographic (bioautographic) techniques are definitely superior for assay and for dereplication purposes. A prescreen assay system which combines the advantages and minimizes the disadvantages of the two approaches is described.

Bacterial metabolism of anthracycline antibiotics. Steffimycinone and steffimycinol conversions.

Streptomyces nogalater, UC-2783, and Streptomyces peucetius var. caesius, IMRU-3920/UC-5633, catalyze ketonic carbonyl reduction of steffimycinone (1, Scheme 1). Using cell-free preparations of S. nogalater, the process of ketonic carbonyl reduction has been shown to be TPNH linked. The product, steffimycinol (2), is reduced further by Aeromonas hydrophila, 2C/UC-6303, by the process of microaerophilic conversion of anthracyclinones previously reported1,2) with the result being the formation of 7-deoxysteffimycinol (3). The products (2 and 3) were isolated by extraction from the fermentations followed by chromatographic purification. Identification was by comparison of various physical properties and spectral data with those of authentic materials obtained by chemical means. Catalytic activity of the crude enzyme preparations of S. nogalater was lost by dialysis by restored by addition of TPNH although not by addition of DPNH demonstrating TPNH dependence. The reaction rate increased linearly with added crude enzyme protein up to 4 mg/ml and was highest between pH 6.5 and 7.0.

Analogs and conversion products of streptozotocin.

Reduction of the nitroso group in streptozotocin (1a) has led to cyclized products rather than a semicarbazide (1c). Some analogs (1e, 9a, 9b, 9c and 9d) of streptozotocin in which the nitroso group was replaced by other groups have been prepared.