Neutron diffraction structure of melampodin: its role in the reclassification of the germacranolides.

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  • Author(s): Watkins SF;Watkins SF; Fischer NH; Bernal I
  • Source:
    Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 1973 Aug; Vol. 70 (8), pp. 2434-8.
  • Publication Type:
    Journal Article
  • Language:
    English
  • Additional Information
    • Source:
      Publisher: National Academy of Sciences Country of Publication: United States NLM ID: 7505876 Publication Model: Print Cited Medium: Print ISSN: 0027-8424 (Print) Linking ISSN: 00278424 NLM ISO Abbreviation: Proc Natl Acad Sci U S A Subsets: PubMed not MEDLINE
    • Publication Information:
      Original Publication: Washington, DC : National Academy of Sciences
    • Abstract:
      The precise crystal and molecular structure of melampodin, C(21)H(24)O(9), was determined from three-dimensional neutron diffraction data collected by counter techniques and phases by direct statistical methods. Crystals are orthorhombic, P2(1)2(1)2(1), a = 8,990(9), b = 14.352(14), c = 16.294(16) A, V = 2102 A(3), d(calc.) = 1.328 g.cm(-3), Z = 4 molecules per unit cell. The structural model was refined by full matrix least-squares of 2303 observed independent reflections, with all 54 atoms treated anisotropically, to R(F) = 5.0%. Hydrogen bonds link melampodin molecules together in the solid state. The conformation of the cyclodeca-1,5-diene ring is such that one intraannular hydrogen atom interacts strongly with one double bond, but there is little or no transannular interaction between double bonds. Strain in the ten-membered ring and in the trans-fused lactone ring is discussed, as are chemical implications of the unsymmetric epoxide in the epoxyangelic acid side chain. The previously suggested reclassification of germacranolide sesquiterpene lactones into four subgroups is supported, and a new convention for configurational representations of the four subgroups is proposed.
    • References:
      Science. 1972 Dec 22;178(4067):1282-3. (PMID: 17792122)
      J Am Chem Soc. 1971 Sep;93(19):4916-8. (PMID: 5165740)
      Trans N Y Acad Sci. 1970 Jan;32(1):85-106. (PMID: 5265129)
      J Am Chem Soc. 1971 Sep;93(19):4914-6. (PMID: 5165739)
    • Publication Date:
      Date Created: 19730801 Date Completed: 20100629 Latest Revision: 20190501
    • Publication Date:
      20231215
    • Accession Number:
      PMC433751
    • Accession Number:
      10.1073/pnas.70.8.2434
    • Accession Number:
      16592106