Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2014-10-11
    Description: Cycloaddition is an essential tool in chemical synthesis. Instead of using light or heat as a driving force, marine sponges promote cycloaddition with a more versatile but poorly understood mechanism in producing pyrrole-imidazole alkaloids sceptrin, massadine, and ageliferin. Through de novo synthesis of sceptrin and massadine, we show that sponges may use single-electron oxidation as a central mechanism to promote three different types of cycloaddition. Additionally, we provide surprising evidence that, in contrast to previous reports, sceptrin, massadine, and ageliferin have mismatched chirality. Therefore, massadine cannot be an oxidative rearrangement product of sceptrin or ageliferin, as is commonly believed. Taken together, our results demonstrate unconventional chemical approaches to achieving cycloaddition reactions in synthesis and uncover enantiodivergence as a new biosynthetic paradigm for natural products.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4205478/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4205478/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ma, Zhiqiang -- Wang, Xiaolei -- Wang, Xiao -- Rodriguez, Rodrigo A -- Moore, Curtis E -- Gao, Shuanhu -- Tan, Xianghui -- Ma, Yuyong -- Rheingold, Arnold L -- Baran, Phil S -- Chen, Chuo -- R01 GM073949/GM/NIGMS NIH HHS/ -- R01 GM079554/GM/NIGMS NIH HHS/ -- R01-GM073949/GM/NIGMS NIH HHS/ -- R01-GM079554/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2014 Oct 10;346(6206):219-24. doi: 10.1126/science.1255677.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. ; Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA. ; Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA. ; Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. chuo.chen@utsouthwestern.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25301624" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biosynthetic Pathways ; *Cycloaddition Reaction ; Molecular Structure ; Porifera/*metabolism ; Pyrroles/*chemical synthesis/chemistry/metabolism ; Stereoisomerism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2015-07-15
    Description: Sherman et al. commented on the precedence of enantiodivergence, listing a number of congeneric natural products with opposite chirality. However, these "congeners" are not derived from enantiodivergent biosyntheses. Instead, they are antipodes arising from separate enantiomeric biosyntheses. A distinct feature of the biosynthesis of the cyclic pyrrole-imidazole dimers is the production of antipodal congeners without the corresponding enantiomers.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4536548/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4536548/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ma, Zhiqiang -- Wang, Xiaolei -- Wang, Xiao -- Rodriguez, Rodrigo A -- Moore, Curtis E -- Gao, Shuanhu -- Tan, Xianghui -- Ma, Yuyong -- Rheingold, Arnold L -- Baran, Phil S -- Chen, Chuo -- R01 GM073949/GM/NIGMS NIH HHS/ -- R01 GM079554/GM/NIGMS NIH HHS/ -- R01-GM073949/GM/NIGMS NIH HHS/ -- R01-GM079554/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2015 Jul 10;349(6244):149. doi: 10.1126/science.aaa9626. Epub 2015 Jul 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. chuo.chen@utsouthwestern.edu. ; Department of Biochemistry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. ; Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA. ; Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26160939" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Cycloaddition Reaction ; Porifera/*metabolism ; Pyrroles/*chemical synthesis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Eine neue organische Substanz, 3, 3′-bis (trifluoromethyl)tetranitrodiphenylamine ist synthetisch hergestellt worden. Die antibakteriellen Eigenschaften gegen Gram-positive Bakterien und gegen Sulfadiazin resistente und empfindliche Arten vonNeisseria meningitidis werden beschrieben.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 217 (1968), S. 350-350 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It was found that a sealed tube reaction was feasible when a slurry of equal amounts of 3,5-dimethylaniline and its hydrochloride, not exceeding a total of 7 g, was packed into a glass tube by means of a glass wool plug. The tube, selected to have a volume of 3 ml./g of material, was sealed and ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 34 (1962), S. 1503-1504 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0020-7608
    Keywords: diacetylene ; dimer ; C8H4 ; ab initio ; DFT ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geometry optimizations were performed for singlet, triplet, and quintet states on the planar structures (in C2h and C2v symmetries) of the diacetylene dimer, using restricted open-shell Hartree-Fock (ROHF), unrestricted Hartree-Fock (UHF), and unrestricted hybrid density functional theory (UB3LYP) methods, with 6-31G(d) and 6-311G(d, p) basis sets. The 1Ag state of the planar van der Waals dimer is lower in energy than are any covalently bonded dimers. At our best B3LYP/6-311G(d, p) level, the most stable covalently bonded diacetylene dimer is the 3Bu state in C2h symmetry, 11 kcal mol-1 above the van der Waals dimer, followed by the 3B2 state in C2v symmetry with 13 kcal mol-1 above the van der Waals dimer. Both structures were confirmed to be local minima. The two diacetylene monomers of these structures are bridged through a single bond and they exhibit a small bend at the neighboring carbons to the bridge, trans to the hydrogens. The 1Bu and 5Ag states in C2h and the 1B2 and 5A1 states in C2v are between 39 and 43 kcal mol-1 above the van der Waals dimer.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 189-202, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-1459
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The absorption spectrum of Sii in the wavelength region 1500–1900 Å has been photographed at high resolution. The silicon vapour was produced in a 122 cm long King furnace at 1800–2300°C. Forty-two Rydberg series have been observed from the ground state terms 3p 2 3 P and1 D to terms associated with the 3pns and 3pnd configurations. All of the series from these configurations withJ〈4 have been extended with the 3pnd 3 D 3 o levels reachingn=56. Numerous perturbations have been observed. This laboratory work has provided the basis for extending the identification of silicon lines in the solar spectrum. Nearly all lines found in the laboratory spectrum are also found in rocket spectrograms of the solar chromosphere. More than 300 lines have been attributed to Sii. The excellent correlation between laboratory and solar Sii lines will be illustrated.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...