[Journal logo]

Volume 69 
Part 8 
Page o1290  
August 2013  

Received 10 July 2013
Accepted 16 July 2013
Online 20 July 2013

Key indicators
Single-crystal X-ray study
T = 200 K
Mean [sigma](C-C) = 0.004 Å
R = 0.043
wR = 0.100
Data-to-parameter ratio = 13.9
Details
Open access

Isotenulin

aDepartment of Chemistry, The University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA
Correspondence e-mail: kyle-knight@utc.edu

Isotenulin, C17H22O5, is a sesquiterpene lactone isolated from sneezeweed Helenium amarum. It crystallizes with two independent molecules in the asymmetric unit. In each molecule, two five-membered rings (cyclopentenone and lactone) are trans-fused to the central seven-membered ring. The five-membered rings each adopt envelope conformations. The seven-membered ring adopts a twist-chair conformation. In the crystal, the molecules are linked by C-H...O interactions, which generate a three-dimensional network.

Related literature

For the discovery and structural identification of tenulin, see: Clark (1939[Clark, E. P. (1939). J. Am. Chem. Soc. 61, 1836-1840.]); Herz et al. (1975[Herz, W. & Sharma, R. P. (1975). J. Org. Chem. 40, 2557-2559.]); Braun et al. (1956[Braun, B. H., Herz, W. & Rabindran, K. (1956). J. Am. Chem. Soc. 78, 4423-4429.]); Barton et al. (1956[Barton, D. H. R. & De Mayo, P. (1956). J. Chem. Soc. pp. 142-149.]). For biological activity that has been observed for tenulin and its analogs, see: Lee et al. (1977[Lee, K. H., Hall, I. H., Mar, E. C., Starnes, C. O., ElGebaly, S. A., Waddell, T. G., Hadgraft, R. I., Ruffner, C. G. & Weidner, I. (1977). Science, 196, 533-536.]); Li et al. (2008[Li, X.-J. & Zhang, H.-Y. (2008). Trends Mol. Med. 14, 1-2.]); Hodge et al. (1995[Hodge, J. S. & Waddell, T. G. (1995). J. Nat. Prod. 58, 149-151.], and references therein). For the crystal structure of tenulin, see: Knight et al. (2013[Knight, K. S., Smith, C. T., Waddell, T. G. & Noll, B. (2013). Acta Cryst. E69, o1237-o1238.]). For the crystal structure of bromoisotenulin, see: Mazhar-Ul-Haque et al. (1974[Mazhar-Ul-Haque, Rogers, D. & Caughlan, C. N. (1974). J. Chem. Soc. Perkin Trans. 2, pp. 223-228.]).

[Scheme 1]

Experimental

Crystal data
  • C17H22O5

  • Mr = 306.34

  • Orthorhombic, P 21 21 21

  • a = 6.4565 (11) Å

  • b = 17.625 (3) Å

  • c = 27.997 (4) Å

  • V = 3186.0 (9) Å3

  • Z = 8

  • Mo K[alpha] radiation

  • [mu] = 0.09 mm-1

  • T = 200 K

  • 0.55 × 0.3 × 0.2 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • 34729 measured reflections

  • 5611 independent reflections

  • 4883 reflections with I > 2[sigma](I)

  • Rint = 0.047

Refinement
  • R[F2 > 2[sigma](F2)] = 0.043

  • wR(F2) = 0.100

  • S = 1.01

  • 5611 reflections

  • 405 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 0.13 e Å-3

  • [Delta][rho]min = -0.17 e Å-3

Table 1
Hydrogen-bond geometry (Å, °)

D-H...A D-H H...A D...A D-H...A
C4-H4...O4i 1.00 2.50 3.324 (4) 139
C21-H21...O5ii 1.00 2.44 3.421 (4) 167
Symmetry codes: (i) [x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]; (ii) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: APEX2 (Bruker, 2009[Bruker (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2009[Bruker (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]); software used to prepare material for publication: OLEX2.


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CV5424 ).


Acknowledgements

Acknowledgements are made to the National Science Foundation MRI Program (CHE-0951711) and the Grote Chemistry Fund at the University of Tennessee at Chattanooga for their generous support of our work.

References

Barton, D. H. R. & De Mayo, P. (1956). J. Chem. Soc. pp. 142-149.  [CrossRef]
Braun, B. H., Herz, W. & Rabindran, K. (1956). J. Am. Chem. Soc. 78, 4423-4429.  [CrossRef] [ChemPort] [Web of Science]
Bruker (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.
Clark, E. P. (1939). J. Am. Chem. Soc. 61, 1836-1840.  [CrossRef] [ChemPort]
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.  [Web of Science] [CrossRef] [ChemPort] [IUCr Journals]
Herz, W. & Sharma, R. P. (1975). J. Org. Chem. 40, 2557-2559.  [CrossRef] [ChemPort]
Hodge, J. S. & Waddell, T. G. (1995). J. Nat. Prod. 58, 149-151.  [CrossRef] [ChemPort] [Web of Science]
Knight, K. S., Smith, C. T., Waddell, T. G. & Noll, B. (2013). Acta Cryst. E69, o1237-o1238.  [CrossRef] [IUCr Journals]
Lee, K. H., Hall, I. H., Mar, E. C., Starnes, C. O., ElGebaly, S. A., Waddell, T. G., Hadgraft, R. I., Ruffner, C. G. & Weidner, I. (1977). Science, 196, 533-536.  [CrossRef] [PubMed] [ChemPort] [Web of Science]
Li, X.-J. & Zhang, H.-Y. (2008). Trends Mol. Med. 14, 1-2.  [Web of Science] [CrossRef] [PubMed]
Mazhar-Ul-Haque, Rogers, D. & Caughlan, C. N. (1974). J. Chem. Soc. Perkin Trans. 2, pp. 223-228.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.  [CrossRef] [ChemPort] [IUCr Journals]


Acta Cryst (2013). E69, o1290  [ doi:10.1107/S1600536813019703 ]

This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.