11β,13-Dihydro­lactucin-8-O-acetate hemihydrate

Fronczek, C.F.; Gomez-Barrios, M.L.; Fischer, N.H.; Fronczek, F.R.

doi:10.1107/S160053680903829X

Volume 65
Part 10
Pages o2564-o2565
October 2009

Received 16 September 2009
Accepted 21 September 2009
Online 30 September 2009

Key indicators
Single-crystal X-ray study
T = 90 K
Mean (C-C) = 0.002 Å
R = 0.027
wR = 0.068
Data-to-parameter ratio = 12.7
Details

11,13-Dihydrolactucin-8-O-acetate hemihydrate

Chris F. Fronczek,^a Marco L. Gomez-Barrios,^a Nikolaus H. Fischer ^a and Frank R. Fronczek ^a ^*

^aDepartment of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804, USA
Correspondence e-mail: ffroncz@lsu.edu

The title structure (systematic name: 9-hydroxymethyl-3,6-dimethyl-3-methylene-2,7-dioxo-3,3a,4,5,9a,9b-hexahydroazuleno[4,5-b]furan-4-yl acetate hemihydrate), C₁₇H₂₀O₆·0.5H₂O, from Lactuca floridana, has two independent sesquiterpene lactone molecules in the asymmetric unit. Both have their seven-membered rings in the chair conformation. In the crystal, the OH groups and the water molecule form classical O-HO hydrogen bonds with OO distances in the range 2.6750 (17)-2.8160 (18) Å.

Related literature

For phytochemical reports of the title compound, see: Bohlmann et al. (1981); Djordjevic et al. (2004); Sarg et al. (1982); Song et al. (1995). The crystal structures of several related compounds have been reported: 8- [alpha] -hydroxyachillin (Campos et al., 1989); matricarin (Parvez et al., 2002); lactucin (Ruban et al., 1978); lactucopicrin (Ren et al., 2003); absolute configuration of sesquiterpene lactones Fischer et al. (1979). For analysis of Bijvoet pairs, see: Hooft et al. (2008).

Experimental

Crystal data

C₁₇H₂₀O₆·0.5H₂O
M_r = 329.34
Monoclinic, P 2₁
a = 10.9276 (5) Å
b = 7.4658 (5) Å
c = 19.8571 (10) Å
= 100.850 (5)°
V = 1591.05 (15) Å³
Z = 4
Cu K radiation
= 0.88 mm^-1
T = 90 K
0.27 × 0.17 × 0.10 mm

Data collection

Bruker Kappa APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004) T_min = 0.796, T_max = 0.917
23565 measured reflections
5642 independent reflections
5513 reflections with I > 2(I)
R_int = 0.031

Refinement

R[F² > 2(F²)] = 0.027
wR(F²) = 0.068
S = 1.03
5642 reflections
445 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
_max = 0.20 e Å^-3
_min = -0.14 e Å^-3
Absolute structure: Flack (1983), 2516 Friedel pairs
Flack parameter: -0.01 (10)

Table 1
Hydrogen-bond geometry (Å, °)

D-HA	D-H	HA	DA	D-HA
O6-H6OO7	0.86 (2)	1.85 (2)	2.6750 (17)	160 (2)
O6A-H60AO6	0.85 (2)	1.91 (2)	2.7593 (17)	174 (2)
O7-H72O5Aⁱ	0.89 (2)	1.95 (2)	2.8160 (18)	165 (2)
O7-H71O6Aⁱⁱ	0.89 (3)	1.86 (3)	2.7397 (18)	176 (3)
Symmetry codes: (i) $[-x+1, y+{\script{1\over 2}}, -z+1]$ ; (ii) x, y+1, z.

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXTL.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2210 ).

Acknowledgements

We are grateful to Rosalind Segesta for financial assistance with the open-access fee.

References

Bohlmann, F., Jakupovic, J., Abraham, W.-R. & Zdero, C. (1981). Phytochemistry, 20, 2371-2374.
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Campos, V., Silva, M., Watson, W. H. & Nagl, A. (1989). Acta Cryst. C45, 678-680.
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Ren, Y.-L., Zhou, Y.-W. & Ye, Y.-H. (2003). Struct. Chem. 14, 581-585.
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Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Song, Q., Gomez-Barrios, M. L., Hopper, E. L., Hjortso, M. A. & Fischer, N. H. (1995). Phytochemistry, 40, 1659-1665.

organic compounds