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The Journal of Antibiotics Jan 1991Chemical modification of the side chain in rhizoxin, a potent antimitotic agent, was attempted in order to study structure-activity relationships and also to devise a...
Chemical modification of the side chain in rhizoxin, a potent antimitotic agent, was attempted in order to study structure-activity relationships and also to devise a probe for photoaffinity labeling of tubulin. An OsO4/NaIO4 oxidation gave a nor-rhizoxin 20-al (5) which was converted to 20-ol (6) by a NaBH3CN reduction. Starting from these two compounds as key intermediates, a series of Wittig reaction products 7-2, and of 20-O-acylates 13-21 were prepared and their anti-tubulin activity and cytotoxicity were determined. An aryl azide derivative 23 was synthesized as a photoaffinity analogue.
Topics: Animals; Antibiotics, Antineoplastic; Isomerism; Lactones; Leukemia P388; Macrolides; Molecular Conformation; Structure-Activity Relationship; Tubulin Modulators; Tumor Cells, Cultured
PubMed: 2001986
DOI: 10.7164/antibiotics.44.66 -
Archives of Biochemistry and Biophysics Sep 2022A tritiated derivative of the sponge-derived natural product spongistatin 1 was prepared, and its interactions with tubulin were examined. [H]Spongistatin 1 was found to...
A tritiated derivative of the sponge-derived natural product spongistatin 1 was prepared, and its interactions with tubulin were examined. [H]Spongistatin 1 was found to bind rapidly to tubulin at a single site (the low specific activity of the [H]spongistatin 1, 0.75 Ci/mmol, prevented our defining an association rate), and the inability of spongistatin 1 to cause an aberrant assembly reaction was confirmed. Spongistatin 1 bound to tubulin very tightly, and we could detect no significant dissociation reaction from tubulin. The tubulin-[H]spongistatin 1 complex did dissociate in 8 M urea, so there was no evidence for covalent bond formation. Apparent K values were obtained by Scatchard analysis of binding data and by Hummel-Dreyer chromatography (3.5 and 1.1 μM, respectively). The effects of a large cohort of vinca domain drugs on the binding of [H]spongistatin 1 to tubulin were evaluated. Compounds that did not cause aberrant assembly reactions (halichondrin B, eribulin, maytansine, and rhizoxin) caused little inhibition of [H]spongistatin 1 binding. Little inhibition also occurred with the peptides dolastatin 15, its active pentapeptide derivative, vitilevuamide, or diazonamide A, nor with the vinca alkaloid vinblastine. Strong inhibition was observed with dolastatin 10, hemiasterlin, and cryptophycin 1, all of which cause aberrant assembly reactions that might actually mask the spongistatin 1 binding site. Spongistatin 5 was found to be a competitive inhibitor of [H]spongistatin 1 binding, with an apparent K of 2.2 μM. We propose that the strong picomolar cytotoxicity of spongistatin 1 probably derives from its extremely tight binding to tubulin.
Topics: Antineoplastic Agents; Binding Sites; Macrolides; Microtubules; Tubulin; Vinblastine
PubMed: 35594923
DOI: 10.1016/j.abb.2022.109296 -
Angewandte Chemie (International Ed. in... Jan 2001
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Chembiochem : a European Journal of... Oct 2011Chain armor against tumor cells: The oxazole side chain in the antimitotic agent rhizoxin S2 (1) was successfully replaced through mutasynthesis by using an engineered...
Chain armor against tumor cells: The oxazole side chain in the antimitotic agent rhizoxin S2 (1) was successfully replaced through mutasynthesis by using an engineered mutant impaired in heterocyclization. Incorporation of 12 non-natural surrogates into fully processed rhizoxin analogues revealed a remarkable substrate flexibility of the PKS-NRPS hybrid.
Topics: Amino Acid Sequence; Antibiotics, Antineoplastic; Burkholderia; Genes, Fungal; Genetic Loci; Macrolides; Molecular Sequence Data; Mutation; Oxazoles; Peptide Synthases; Polyketide Synthases
PubMed: 23106078
DOI: 10.1002/cbic.201100387 -
The ISME Journal Jun 2008The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic Burkholderia sp. for the production of the virulence factor, the antimitotic agent rhizoxin....
The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic Burkholderia sp. for the production of the virulence factor, the antimitotic agent rhizoxin. Since the toxin highly efficiently blocks mitosis in most eukaryotes, it remained elusive how self-resistance emerged in the fungal host. In this study, rhizoxin sensitivity was systematically correlated with the nature of beta-tubulin sequences in the kingdom Fungi. A total of 49 new beta-tubulin sequences were generated for representative species of Ascomycota, Basidiomycota and Zygomycota. Rhizoxin sensitivity assays revealed two further amino acids at position 100 (Ser-100 and Ala-100), in addition to the known Ile-100 and Val-100, which convey rhizoxin resistance. All sensitive strains feature Asn-100. This hot spot was verified by modeling studies, which support the finding that rhizoxin preferentially interacts with the tubulin molecule in a cavity near position 100. Ancestral character state reconstructions conducted in a Bayesian framework suggest that rhizoxin sensitivity represents the ancestral character state in fungi, and that evolution of rhizoxin resistance took place in the ancestor of extant resistant Zygomycota. These findings support a model according to which endosymbiosis became possible through a parasitism--mutualism shift in insensitive fungi.
Topics: Amino Acid Sequence; Bacterial Toxins; Burkholderia; Drug Resistance, Fungal; Evolution, Molecular; Fungal Proteins; Fungi; Macrolides; Models, Molecular; Molecular Sequence Data; Phylogeny; Protein Binding; Rhizopus; Symbiosis; Tubulin
PubMed: 18309361
DOI: 10.1038/ismej.2008.19 -
The Journal of Organic Chemistry Nov 2002Rhizoxin D (2) was synthesized from four subunits, A, B, C, and D representing C3-C9, C10-C13, C14-C19, and C20-C27, respectively. Subunit A was prepared by cyclization...
Rhizoxin D (2) was synthesized from four subunits, A, B, C, and D representing C3-C9, C10-C13, C14-C19, and C20-C27, respectively. Subunit A was prepared by cyclization of iodo acetal 21, which set the configuration at C5 of 2 through a stereoselective addition of the radical derived from dehalogenation of 21 at the beta carbon of the (Z)-alpha,beta-unsaturated ester. Aldehyde 29 was obtained from phenylthioacetal 24 and condensed with phosphorane 30, representing subunit B, in a Wittig reaction that gave the (E,E)-dienoate 31. This ester was converted to aldehyde 33 in preparation for coupling with subunit C. The latter in the form of methyl ketone 55 was obtained in six steps from propargyl alcohol. An aldol reaction of 33 with the enolate of 55 prepared with (+)-DIPCl gave the desired beta-hydroxy ketone 56 bearing a (13S)-configuration in a 17-20:1 ratio with its (13R)-diastereomer. After reduction to anti diol 57 and selective protection as TIPS ether 58, the C15 hydroxyl was esterified to give phosphonate 59. An intramolecular Wadsworth-Emmons reaction of aldehyde 62, derived from delta-lactone 60, furnished macrolactone 63, which was coupled in a Stille reaction with stannane 68 to give 2 after cleavage of the TIPS ether.
Topics: Antineoplastic Agents; Lactones; Molecular Structure; Rhizopus
PubMed: 12398499
DOI: 10.1021/jo020537q -
Molecules (Basel, Switzerland) Oct 2020Efforts are described towards the total synthesis of the bacterial macrolide rhizoxin F, which is a potent tubulin assembly and cancer cell growth inhibitor. A...
Efforts are described towards the total synthesis of the bacterial macrolide rhizoxin F, which is a potent tubulin assembly and cancer cell growth inhibitor. A significant amount of work was expanded on the construction of the rhizoxin core macrocycle by ring-closing olefin metathesis (RCM) between C(9) and C(10), either directly or by using relay substrates, but in no case was ring-closure achieved. Macrocycle formation was possible by ring-closing alkyne metathesis (RCAM) at the C(9)/C(10) site. The requisite diyne was obtained from advanced intermediates that had been prepared as part of the synthesis of the RCM substrates. While the direct conversion of the triple bond formed in the ring-closing step into the C(9)-C(10) double bond of the rhizoxin macrocycle proved to be elusive, the corresponding Z isomer was accessible with high selectivity by reductive decomplexation of the biscobalt hexacarbonyl complex of the triple bond with ethylpiperidinium hypophosphite. Radical-induced double bond isomerization, full elaboration of the C(15) side chain, and directed epoxidation of the C(11)-C(12) double bond completed the total synthesis of rhizoxin F.
Topics: Acids; Alkenes; Alkynes; Cyclization; Macrolides; Models, Molecular
PubMed: 33023218
DOI: 10.3390/molecules25194527 -
Chembiochem : a European Journal of... Jan 2007
Topics: Antimitotic Agents; Burkholderia; Chromatography, High Pressure Liquid; Cosmids; Fungi; Gene Library; Macrolides; Models, Chemical; Multigene Family; Mutation; Rhizopus; Sequence Analysis, DNA; Symbiosis; Time Factors
PubMed: 17154220
DOI: 10.1002/cbic.200600393 -
Comprehensive Reviews in Food Science... Nov 2022Fermented soybean products are widely consumed worldwide, and their popularity is increasing. Filamentous fungi, such as Actinomucor, Aspergillus, Monascus, Mucor,... (Review)
Review
Fermented soybean products are widely consumed worldwide, and their popularity is increasing. Filamentous fungi, such as Actinomucor, Aspergillus, Monascus, Mucor, Penicillium, Rhizopus, and Zymomonas, play critical roles in the fermentation processes of many soybean foods. However, besides producing essential enzymes for food fermentation, filamentous fungi can release undesirable or even toxic metabolites into the food. Mycotoxins are toxic secondary metabolites produced by certain filamentous fungi and may be detected during the food production process. Without effective prevention strategies, mycotoxin contamination in fermented soybean products poses a risk to human health. This review focused on the changes in mycotoxigenic fungal abundance and mycotoxin contamination at different stages during the production of soybean-based fermented foods, as well as effective strategies for preventing mycotoxin contamination in such products. Data from relevant studies demonstrated a tendency of change in the genera of mycotoxigenic fungi and types of mycotoxins (aflatoxins, alternariol, alternariol monomethyl ether, deoxynivalenol, fumonisins, ochratoxin A, rhizoxins, T-2 toxin, and zearalenone) present in the raw materials and the middle and final products. The applicability of traditional chemical and physical mitigation strategies and novel eco-friendly biocontrol approaches to prevent mycotoxin contamination in soybean-based fermented foods were discussed. The present review highlights the risks of mycotoxin contamination during the production of fermented soybean products and recommends promising strategies for eliminating mycotoxin contamination risk in soybean-based fermented foods.
Topics: Humans; Mycotoxins; Glycine max; Food Contamination; Fumonisins; Fungi
PubMed: 36084140
DOI: 10.1111/1541-4337.13032 -
Organic & Biomolecular Chemistry Aug 2012Through metabolic profiling of mutants and wild type of the endofungal bacterium Burkholderia rhizoxinica two novel rhizoxin derivatives with unusual nitrile...
Through metabolic profiling of mutants and wild type of the endofungal bacterium Burkholderia rhizoxinica two novel rhizoxin derivatives with unusual nitrile substitutions were discovered. The nitrile groups result from a photochemical oxidative cleavage of the oxazolyl moiety. In vitro studies revealed that the photooxidation by singlet oxygen also takes place in the absence of a photosensitizer, and that also a thiazolyl-substituted rhizoxin analogue undergoes the same transformation. The resulting nitriles have antimitotic properties but are significantly less active than the parent compounds. These results highlight the impact of photoreactions onto the antiproliferative agent and encourage the introduction of bioisosteric groups that render the compound less susceptible towards photooxidation.
Topics: Antimitotic Agents; Cell Line, Tumor; Humans; Macrolides; Nitriles; Oxazoles; Photochemical Processes
PubMed: 22453231
DOI: 10.1039/c2ob25250c