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K C Nicolaou, Pengxi Chen, Shugao Zhu, Quan Cai, Rohan D Erande, Ruofan Li, Hongbao Sun, Kiran Kumar Pulukuri, Stephan Rigol, Monette Aujay, Joseph Sandoval, Julia Gavrilyuk
A streamlined total synthesis of the naturally occurring antitumor agents trioxacarcins is described, along with its application to the construction of a series of designed analogues of these complex natural products. Biological evaluation of the synthesized compounds revealed a number of highly potent, and yet structurally simpler, compounds that are effective against certain cancer cell lines, including a drug-resistant line. A novel one-step synthesis of anthraquinones and chloro anthraquinones from simple ketone precursors and phenylselenyl chloride is also described...
November 1, 2017: Journal of the American Chemical Society
K C Nicolaou, Quan Cai, Hongbao Sun, Bo Qin, Shugao Zhu
Trioxacarcins DC-45-A2, DC-45-A1, A, D, C7″-epi-C, and C have been synthesized through stereoselective strategies involving BF3·Et2O-catalyzed ketone-epoxide opening and gold-catalyzed glycosylation reactions, and the full structural assignment of trioxacacin C was deciphered via the syntheses of both of its C7″ epimers. The gathered knowledge sets the foundation for the design, synthesis, and biological evalution of analogues of these natural products as potential payloads for antibody-drug conjugates and other delivery systems for targeted and personalized cancer chemotherapy...
March 9, 2016: Journal of the American Chemical Society
Kui Yang, Li-Hua Qi, Mei Zhang, Xian-Feng Hou, Hai-Xue Pan, Gong-Li Tang, Wei Wang, Hua Yuan
Trioxacarcin A is a polyoxygenated, structurally complex antibiotic produced by Streptomyces spp., which possesses high anti-bacterial, anti-malaria, and anti-tumor activities. The trioxacarcin biosynthetic pathway involves type II polyketide synthases (PKSs) with L-isoleucine as a unique starter unit, as well as many complex post-PKS tailoring enzymes and resistance and regulatory proteins. In this work, two regulatory genes, txn9 coding for a Streptomyces antibiotic regulatory protein family regulator and txn11 for a two-component response regulator, were revealed to be absolutely required for trioxacarcin production by individually inactivating all the six annotated regulatory genes in the txn cluster...
October 2015: Current Microbiology
K C Nicolaou, Quan Cai, Bo Qin, Mette T Petersen, Remi J T Mikkelsen, Philipp Heretsch
An enantioselective total synthesis of trioxacarcin DC-45-A2 (1) featuring a novel Lewis acid-induced cascade rearrangement of epoxyketone 6 to forge the polyoxygenated 2,7-dioxabicyclo[2.2.1]heptane core of the molecule is described.
March 2, 2015: Angewandte Chemie
Kevin Pröpper, Birger Dittrich, Daniel J Smaltz, Thomas Magauer, Andrew G Myers
X-ray crystallographic characterization of products derived from natural and fully synthetic trioxacarcins, molecules with potent antiproliferative effects, illuminates aspects of their reactivity and mechanism of action. Incubation of the fully synthetic trioxacarcin analog 3, which lacks one of the carbohydrate residues present in the natural product trioxacarcin A (1) as well as oxygenation at C2 and C4 yet retains potent antiproliferative effects, with the self-complimentary duplex oligonucleotide d(AACCGGTT) led to production of a crystalline covalent guanine adduct (6)...
September 15, 2014: Bioorganic & Medicinal Chemistry Letters
Thomas Magauer, Daniel J Smaltz, Andrew G Myers
The trioxacarcins are polyoxygenated, structurally complex natural products that potently inhibit the growth of cultured human cancer cells. Here we describe syntheses of trioxacarcin A, DC-45-A1 and structural analogues by late-stage stereoselective glycosylation reactions of fully functionalized, differentially protected aglycon substrates. Key issues addressed in this work include the identification of an appropriate means to activate and protect each of the two 2-deoxysugar components, trioxacarcinose A and trioxacarcinose B, as well as a viable sequencing of the glycosidic couplings...
October 2013: Nature Chemistry
Jakub Švenda, Nicholas Hill, Andrew G Myers
Many first-line cancer drugs are natural products or are derived from them by chemical modification. The trioxacarcins are an emerging class of molecules of microbial origin with potent antiproliferative effects, which may derive from their ability to covalently modify duplex DNA. All trioxacarcins appear to be derivatives of a nonglycosylated natural product known as DC-45-A2. To explore the potential of the trioxacarcins for the development of small-molecule drugs and probes, we have designed a synthetic strategy toward the trioxacarcin scaffold that enables access to both the natural trioxacarcins and nonnatural structural variants...
April 26, 2011: Proceedings of the National Academy of Sciences of the United States of America
Roland Pfoh, Hartmut Laatsch, George M Sheldrick
We report a crystal structure that shows an antibiotic that extracts a nucleobase from a DNA molecule 'caught in the act' after forming a covalent bond but before departing with the base. The structure of trioxacarcin A covalently bound to double-stranded d(AACCGGTT) was determined to 1.78 A resolution by MAD phasing employing brominated oligonucleotides. The DNA-drug complex has a unique structure that combines alkylation (at the N7 position of a guanine), intercalation (on the 3'-side of the alkylated guanine), and base flip-out...
June 2008: Nucleic Acids Research
Ansgar Fitzner, Holm Frauendorf, Hartmut Laatsch, Ulf Diederichsen
Formation and fragmentation of recognition complexes between trioxacarcin A and various DNA sequences were examined by temperature-dependent UV and CD spectroscopy, HPLC analysis, and ESI mass spectrometry with regard to reaction conditions, intermediates, products, mechanism, and sequence specificity. Cleavage of the trioxacarcin-DNA complexes provided the natural product gutingimycin by guanine abstraction. The resulting DNA with an abasic site was further cleaved into a DNA fragment with a furanyl unit at the 3'-end and an oligonucleotide with a phosphorylated 5'-end...
February 2008: Analytical and Bioanalytical Chemistry
Rajendra P Maskey, Elisabeth Helmke, Oliver Kayser, Heinz H Fiebig, Armin Maier, Andreas Busche, Hartmut Laatsch
The ethyl acetate extract from the Streptomyces sp. isolate B8652 delivered the trioxacarcins A to approximately C (2a to approximately 2c) and additionally three new derivatives designated as trioxacarcins D to approximately F (2d to approximately 2f). All trioxacarcins showed high anti-bacterial and some of them high anti-tumor and anti-malaria activity. The structures of the new antibiotics were derived from mass, 1D and 2D NMR spectra and confirmed by comparison of the NMR data with those of known derivatives...
December 2004: Journal of Antibiotics
F Tomita, T Tamaoki, M Morimoto, K Fujimoto
No abstract text is available yet for this article.
December 1981: Journal of Antibiotics
T Tamaoki, K Shirahata, T Iida, F Tomita
No abstract text is available yet for this article.
December 1981: Journal of Antibiotics
K Fujimoto, M Morimoto
The novel antitumor antibiotic, trioxacarcin C, was studied for antitumor activities against murine tumor systems. When mice with i.p.-inoculated B16 melanoma were given intraperitoneal injections of trioxacarcin C, the maximal T/C% was 164 by successive administration of 0.125 mg/kg/day (day 1 approximately 10). It also gave the prolongation of life span of mice bearing i.p. P388 leukemia (T/C 141%) by i.p. injection for 10 days, and inhibited the growth of sarcoma 180 (T/C 42%) and Lewis lung carcinoma implanted s...
September 1983: Journal of Antibiotics
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