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Volume 57 
Part 4 
Page 499  
April 2001  

Received 6 December 2000
Accepted 18 December 2000

Tricoccin R2. Erratum

aDepartment of Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai 600 025, India,bLaboratory Voor Kristallografie, Nieuwe Achtergracht 166, 1018 WU, Amsterdam, The Netherlands, and cInstitute of Organic Chemistry, University of Kiel, D-2300 Kiel, Olshausenstrasse, Be 40-60, Germany
Correspondence e-mail: partha24@hotmail.com

The crystal structure of the title compound, C25H26O7, was published with erroneous positions for a C atom and the O atom in ring F [Sekar et al. (1996[Sekar, K., Parthasarathy, S., Schenk, H., Epe, B. & Mondon, A. (1996). Acta Cryst. C52, 92-94.]). Acta Cryst. (1996), C52, 92-94 ]. This has now been corrected and leads to a more sensible bond length and angle geometry.

Comment

During a comparative study of the molecular structure of Tricoccin R6 (Abdul Ajees et al., 2001[Abdul Ajees, A., Sekar, K., Parthasarathy, S., Schenk, H., Epe, B. & Mondon, A. (2001). Acta Cryst. E57 o116-117.]) with that of the related compound Tricoccin R2[link] (Sekar et al., 1996[Sekar, K., Parthasarathy, S., Schenk, H., Epe, B. & Mondon, A. (1996). Acta Cryst. C52, 92-94.]) it was found that

[Scheme 1]
the geometry of the molecules in the two structures agreed well except in the region of ring F of Tricoccin R2[link]. This could be traced to a wrong assignment of two of the atoms in ring F of Tricoccin R2[link]. That is, the neighbours of atoms C21 and C22 in ring F of Tricoccin R2 are to be taken as O and C atoms, respectively, instead of C and O as in the original report. The structure of Tricoccin R2[link] thus modified was refined and converged to a lower R value and the final difference Fourier was better. There is now better agreement of the geometry of ring F of Tricoccin R2[link] with that of Tricoccin R6.
[Figure 1]
Figure 1
The molecular structure of the title compound with 30% probability displacement ellipsoids

Experimental

Crystal data
  • C25H26O7

  • Mr = 438.46

  • Monoclinic, C2

  • a = 22.939 (1) Å

  • b = 6.574 (2) Å

  • c = 16.481 (2) Å

  • [beta] = 114.67 (1)°

  • V = 2258.5 (7) Å3

  • Z = 4

  • Dx = 1.289 Mg m-3

  • Cu K[alpha] radiation

  • Cell parameters from 25 reflections

  • [theta] = 20-30°

  • [mu] = 0.78 mm-1

  • T = 293 (2) K

  • Needle, colourless

  • 0.30 × 0.25 × 0.20 mm

Data collection
  • Enraf-Nonius CAD-4 diffractometer

  • [omega]/2[theta] scans

  • Absorption correction: empirical [psi] scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.])Tmin = 0.961, Tmax = 0.991

  • 2312 measured reflections

  • 2230 independent reflections

  • 2054 reflections with I > 2[sigma](I)

  • Rint = 0.027

  • [theta]max = 70.3°

  • h = -25 [rightwards arrow] 27

  • k = 0 [rightwards arrow] 8

  • l = -19 [rightwards arrow] 0

  • 2 standard reflections frequency: 120 min intensity decay: <1%

Refinement
  • Refinement on F2

  • R[F2 > 2[sigma](F2)] = 0.036

  • wR(F2) = 0.103

  • S = 1.07

  • 2230 reflections

  • 293 parameters

  • H-atom parameters constrained

  • w = 1/[[sigma]2(Fo2) + (0.0588P)2 + 0.6138P] where P = (Fo2 + 2Fc2)/3

  • ([Delta]/[sigma])max < 0.001

  • [Delta][rho]max = 0.27 e Å-3

  • [Delta][rho]min = -0.12 e Å-3

  • Extinction correction: SHELXL97

  • Extinction coefficient: 0.0018 (2)

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.])

  • Flack parameter = 0.1 (3)

Data collection: CAD-4 Software (Enraf-Nonius, 1989[Enraf-Nonius (1989). CAD-4 Software. Version 5.0. Enraf-Nonius, Delft, The Netherlands.]); cell refinement: SDP (Frenz, 1978[Frenz, B. A. (1978). The Enraf-Nonius CAD-4 SDP. Computing in Crystallography, edited by H. Schenk, R. Olthof-Hazekamp, H. van Koningsveld & G. C. Bassi, pp. 64-71. Delft University Press.]); data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. Release 97-2. University of Göttingen, Germany.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. Release 97-2. University of Göttingen, Germany.]).


Supplementary data for this paper are available from the IUCr electronic archives (Reference: VJ1131 ). Services for accessing these data are described at the back of the journal.


References

Abdul Ajees, A., Sekar, K., Parthasarathy, S., Schenk, H., Epe, B. & Mondon, A. (2001). Acta Cryst. E57 o116-117. [details]
Enraf-Nonius (1989). CAD-4 Software. Version 5.0. Enraf-Nonius, Delft, The Netherlands.
Flack, H. D. (1983). Acta Cryst. A39, 876-881. [CrossRef] [details]
Frenz, B. A. (1978). The Enraf-Nonius CAD-4 SDP. Computing in Crystallography, edited by H. Schenk, R. Olthof-Hazekamp, H. van Koningsveld & G. C. Bassi, pp. 64-71. Delft University Press.
North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359. [CrossRef] [details]
Sekar, K., Parthasarathy, S., Schenk, H., Epe, B. & Mondon, A. (1996). Acta Cryst. C52, 92-94. [CrossRef] [details]
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. Release 97-2. University of Göttingen, Germany.


Acta Cryst (2001). C57, 499  [ doi:10.1107/S010827010002045X ]