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Shunichi Kusumi Harunobu Nakayama Takumi Kobayashi Hajime Kuriki Yuka Matsumoto Prof. Dr. Daisuke Takahashi Prof. Dr. Kazunobu Toshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18733-18736
An efficient and practical total synthesis of aquayamycin has been accomplished. The highly oxidized and stereochemically complex tetracyclic ring system was constructed using three key reactions: 1) highly diastereoselective 1,2‐addition of C‐glycosyl naphthyllithium to a cyclic ketone, 2) indium‐mediated site‐selective allylation‐rearrangement sequence of naphthoquinone, and 3) diastereoselective intramolecular pinacol coupling. This synthetic strategy offers a novel and efficient pathway to prepare aquayamycin‐type angucycline antibiotics. 相似文献
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Divalent Transition‐Metal‐Ion Stress Induces Prodigiosin Biosynthesis in Streptomyces coelicolor M145: Formation of Coeligiosins
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Dr. Anne Morgenstern Dr. Christian Paetz Dr. Anne Behrend Prof. Dr. Dieter Spiteller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6027-6032
The bacterium Streptomyces coelicolor M145 reacts to transition‐metal‐ion stress with myriad growth responses, leading to different phenotypes. In particular, in the presence of Co2+ ions (0.7 mM ) S. coelicolor consistently produced a red phenotype. This phenotype, when compared to the wild type, differed strongly in its production of volatile compounds as well as high molecular weight secondary metabolites. LC‐MS analysis revealed that in the red phenotype the production of the prodigiosins, undecylprodigiosin and streptorubin B, was strongly induced and, in addition, several intense signals appeared in the LC‐MS chromatogram. Using LC‐MS/MS and NMR spectroscopy, two new prodigiosin derivatives were identified, that is, coeligiosin A and B, which contained an additional undecylpyrrolyl side chain attached to the central carbon of the tripyrrole ring system of undecylprodigiosin or streptorubin B. This example demonstrates that environmental factors such as heavy metal ion stress can not only induce the production of otherwise not observed metabolites from so called sleeping genes but alter the products from well‐studied biosynthetic pathways. 相似文献
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Christopher Selleck Prof. James A. Larrabee Assoc. Prof. Jeffrey Harmer Assoc. Prof. Luke W. Guddat Dr. Nataša Mitić Waleed Helweh Prof. David L. Ollis Dr. Whitney R. Craig Prof. David L. Tierney Dr. Marcelo Monteiro Pedroso Prof. Gerhard Schenk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17704-17714
Antibiotic resistance has emerged as a major threat to global health care. This is largely due to the fact that many pathogens have developed strategies to acquire resistance to antibiotics. Metallo‐β‐lactamases (MBL) have evolved to inactivate most of the commonly used β‐lactam antibiotics. AIM‐1 is one of only a few MBLs from the B3 subgroup that is encoded on a mobile genetic element in a major human pathogen. Here, its mechanism of action was characterised with a combination of spectroscopic and kinetic techniques and compared to that of other MBLs. Unlike other MBLs it appears that AIM‐1 has two avenues available for the turnover of the substrate nitrocefin, distinguished by the identity of the rate‐limiting step. This observation may be relevant with respect to inhibitor design for this group of enzymes as it demonstrates that at least some MBLs are very flexible in terms of interactions with substrates and possibly inhibitors. 相似文献
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Eva‐Maria Christ Sophie S. Müller Elena Berger‐Nicoletti Holger Frey 《Journal of polymer science. Part A, Polymer chemistry》2014,52(19):2850-2859
Synthesis and characterization of novel hydroxyl‐functionalized oxetane‐inimers with varied alkyl chain length—3‐hydroxymethyl‐3‐methoxymethyloxetane, 3‐hydroxymethyl‐3‐propoxymethyloxetane, and 3‐hexoxymethyl‐3‐hydroxymethyloxetane—is reported. Cationic ring‐opening polymerization of these latent, cyclic AB2‐monomers leads to hyperbranched (hb) polyether polyols with degrees of branching between 34 and 69%, confirmed by inverse‐gated (IG) 13C NMR spectroscopy. The hyperbranching polymerization yielded apparent molecular weights (Mn) ranging from 500 to 2500 g mol?1 (size exclusion chromatography). Remarkably, by copolymerization of 1,1,1‐tris(4‐hydroxyphenyl)ethane as a “focal” unit, polymerization under slow monomer addition conditions lead to higher apparent molecular weights up to 11,220 g mol?1. The end groups of the hb polymers were studied via matrix‐assisted laser desorption/ionization time of flight mass and NMR spectrometry. By varying the alkyl chain length, tailoring of the solubility and glass transition temperatures of the materials is possible. Potential applications range from macroinitiators with defined polarity to tailoring of surface properties of antifouling materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2850–2859 相似文献