6β-Hy­droxy­eremophil-7(11)-en-8β,12-olide

Su, R.-N.; Shi, S.; Wu, H.-B.; Wang, W.-S.

doi:10.1107/S1600536811016308

organic compounds

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ISSN: 2056-9890

Volume 67| Part 6| June 2011| Page o1361

doi:10.1107/S1600536811016308

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6β-Hydroxyeremophil-7(11)-en-8β,12-olide

Ri-Na Su,^a Sha Shi,^a Hai-Bo Wu ^a and Wen-Shu Wang ^a ^*

^aCollege of Life and Environment Science, Minzu University of China, Beijing 100081, People's Republic of China
^*Correspondence e-mail: wangws@muc.edu.cn

(Received 18 March 2011; accepted 29 April 2011; online 7 May 2011)

The title eremophilenolide, C₁₅H₂₂O₃, is a natural compound isolated from Senecio laetus Edgew. The two cis-fused six-membered rings have chair confomations and the five-membered ring has a planar envelope conformation [maximum deviation = 0.010 (1) Å]. The β-hydroxy group participates in intermolecular O—H⋯O hydrogen bonding, forming molecular chains along the a axis.

Related literature

For related compounds extracted from Ligularia fischeri and Ligularia duciformis, see: Wang et al. (2000 ) and Fu et al. (2007 ), respectively.

Experimental

Crystal data

C₁₅H₂₂O₃
M_r = 250.33
Orthorhombic, P 2₁ 2₁ 2₁
a = 8.0141 (16) Å
b = 9.969 (2) Å
c = 16.482 (3) Å
V = 1316.8 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 293 K
0.60 × 0.60 × 0.30 mm

Data collection

Rigaku R-AXIS RAPID IP diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ) T_min = 0.950, T_max = 0.975
8965 measured reflections
1744 independent reflections
1314 reflections with I > 2σ(I)
R_int = 0.061

Refinement

R[F² > 2σ(F²)] = 0.047
wR(F²) = 0.107
S = 0.95
1744 reflections
168 parameters
H-atom parameters constrained
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O1ⁱ	0.82	2.18	2.931 (2)	152
Symmetry code: (i) x+1, y, z.

Data collection: RAPID-AUTO (Rigaku, 2000 ); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2000 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811016308/ld2005sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811016308/ld2005Isup2.hkl

checkCIF report

Comment top

Senecio laetus Edgew. grows in Guizhou province of China, and is traditionally used by the locals as medicine having effects on clearing fever and detoxifcation and relieving cough activities. As a part of our research on biological resources in the western area in China, the title compound, an eremophilenolide, was isolated. The compound was identified by NMR spectra, which were compared with the previous reports (Wang et al., 2000; Fu et al., 2007). Herewith, we present its crystal structure. The molecule consists of a fused three-ring system A/B/C(Fig.1). The rings A(C10–C6/C11)and B(C6–C3/C12–C11) are cis-fused; the hydroxy group at C12 site has the same β-orientation as the two methyl groups at C10 and C11. Rings A and B both are in chair conformations. The lactone ring has an envelope-like conformation with the atoms C1-C4 and O2 deviating from its mean plane by -0.002 (1), 0.008 (1), -0.010 (1), 0.007 (1) and -0.003 (1), respectively. The inter-molecular O—H···O hydrogen bonds apparently stabilize the crystal structure linking molecules into chains along [1 0 0].

Related literature top

For related compounds extracted from Ligularia fischeri and Ligularia duciformis, see: Wang et al. (2000) and Fu et al. (2007), respectively.

Experimental top

The air-dried whole plants of Senecio laetus (0.7 kg) were pulverized and triply extracted with MeOH (each time for 7 days) at room temperature. The extract was concentrated to give a residue (67 g), which was further separated by CC (SiO₂, 200–300mesh, petroleum ether/EtOAc (20:1, 15:1, 10:1, 8:1, 5:1, 3:1, 2:1, 1:1 (v/v)) to yield 8 fractions: Fr. 1–8. Each fraction was examined by TLC and combined to afford many subfractions. Fr.5a (0.5 g) was subjected to CC (SiO₂, 200–300mesh, petroleum ether/ EtOAc 10:1, 5:1 (v/v)) to provide the title compound (20 mg). ¹H and ¹³C NMR spectral data of this compound was recorded on Bruker-AV-500 s pectrometer, using CDCl₃ as solvent and Me₄Si as internal standard. The stereochemistry was established by the X-ray diffraction experiment.

Computing details top

Data collection: RAPID-AUTO (Rigaku, 2000); cell refinement: RAPID-AUTO (Rigaku, 2000); data reduction: CrystalStructure (Rigaku/MSC, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. View of the title molecule showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

6β-Hydroxyeremophil-7(11)-en-8β,12-olide top

Crystal data top

C₁₅H₂₂O₃	F(000) = 544
M_r = 250.33	D_x = 1.263 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 8965 reflections
a = 8.0141 (16) Å	θ = 2.4–27.5°
b = 9.969 (2) Å	µ = 0.09 mm⁻¹
c = 16.482 (3) Å	T = 293 K
V = 1316.8 (5) Å³	Block, colourless
Z = 4	0.60 × 0.60 × 0.30 mm

Data collection top

Rigaku R-AXIS RAPID IP diffractometer	1744 independent reflections
Radiation source: fine-focus sealed tube	1314 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.061
ω scans	θ_max = 27.5°, θ_min = 2.4°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = 0→10
T_min = 0.950, T_max = 0.975	k = 0→12
8965 measured reflections	l = 0→21

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.047	H-atom parameters constrained
wR(F²) = 0.107	w = 1/[σ²(F_o²) + (0.0635P)²] where P = (F_o² + 2F_c²)/3
S = 0.95	(Δ/σ)_max = 0.002
1744 reflections	Δρ_max = 0.21 e Å⁻³
168 parameters	Δρ_min = −0.20 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.180 (11)

Crystal data top

C₁₅H₂₂O₃	V = 1316.8 (5) Å³
M_r = 250.33	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 8.0141 (16) Å	µ = 0.09 mm⁻¹
b = 9.969 (2) Å	T = 293 K
c = 16.482 (3) Å	0.60 × 0.60 × 0.30 mm

Data collection top

Rigaku R-AXIS RAPID IP diffractometer	1744 independent reflections
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	1314 reflections with I > 2σ(I)
T_min = 0.950, T_max = 0.975	R_int = 0.061
8965 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.047	0 restraints
wR(F²) = 0.107	H-atom parameters constrained
S = 0.95	Δρ_max = 0.21 e Å⁻³
1744 reflections	Δρ_min = −0.20 e Å⁻³
168 parameters

Special details top

Experimental. Since the two skeleton methyl groups in eremophilenolides are in biogenic β orientation, we assigned the relative stereochemistry of the title eremophilenolide, by reference to the structures of related eremophilenolides in Wang et al. (2000) and Fu et al. (2007) although the absolute configuration could not be reliably determined from anomalous dispersion effects with Mo radiation used in the experiment. Furthermore, the relative stereochemistry in the title compound was confirmed by NMR data. ¹³C NMR(125 MHz, CDCl₃, δ, p.p.m.): 175.15(C1), 162.95(C3), 122.08(C2), 77.55(C4), 70.18(C12), 45.60(C11), 35.88(C5), 35.31(C6), 31.68(C10), 28.33(C7), 28.33(C9), 20.17(C8), 18.96(C14), 15.14(C15), 8.93(C13).

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.1478 (3)	1.0934 (2)	−0.03828 (13)	0.0498 (5)
C2	0.3268 (3)	1.0825 (2)	−0.05855 (13)	0.0440 (5)
C3	0.4112 (3)	1.0805 (2)	0.01139 (12)	0.0413 (5)
C4	0.2914 (2)	1.0938 (3)	0.08081 (12)	0.0481 (6)
H4	0.3130	1.1778	0.1099	0.058*
C5	0.3057 (3)	0.9777 (3)	0.13851 (14)	0.0539 (6)
H5A	0.2681	0.8962	0.1120	0.065*
H5B	0.2354	0.9933	0.1854	0.065*
C6	0.4879 (3)	0.9612 (3)	0.16573 (12)	0.0468 (5)
H6	0.4924	0.8796	0.1989	0.056*
C7	0.5409 (3)	1.0768 (3)	0.22055 (13)	0.0549 (6)
H7A	0.4673	1.0804	0.2672	0.066*
H7B	0.5293	1.1606	0.1911	0.066*
C8	0.7215 (3)	1.0626 (3)	0.24987 (13)	0.0614 (7)
H8A	0.7529	1.1411	0.2811	0.074*
H8B	0.7314	0.9845	0.2846	0.074*
C9	0.8371 (3)	1.0479 (3)	0.17726 (13)	0.0550 (6)
H9A	0.9506	1.0361	0.1965	0.066*
H9B	0.8336	1.1297	0.1455	0.066*
C10	0.7906 (3)	0.9293 (2)	0.12286 (13)	0.0497 (6)
H10	0.8622	0.9345	0.0748	0.060*
C11	0.6069 (2)	0.9379 (2)	0.09238 (12)	0.0427 (5)
C12	0.5903 (2)	1.0574 (2)	0.03156 (12)	0.0413 (5)
H12	0.6343	1.1384	0.0576	0.050*
C13	0.3809 (3)	1.0747 (3)	−0.14545 (12)	0.0561 (6)
H13A	0.4807	1.1265	−0.1528	0.084*
H13B	0.2943	1.1096	−0.1797	0.084*
H13C	0.4024	0.9829	−0.1596	0.084*
C14	0.5597 (3)	0.8095 (2)	0.04675 (15)	0.0633 (7)
H14A	0.6471	0.7864	0.0095	0.095*
H14B	0.4578	0.8239	0.0173	0.095*
H14C	0.5444	0.7377	0.0848	0.095*
C15	0.8317 (4)	0.7963 (3)	0.16557 (18)	0.0727 (8)
H15A	0.9469	0.7961	0.1815	0.109*
H15B	0.8113	0.7230	0.1291	0.109*
H15C	0.7625	0.7867	0.2128	0.109*
O1	0.0277 (2)	1.09467 (19)	−0.08281 (10)	0.0629 (5)
O2	0.12877 (17)	1.09976 (19)	0.04302 (9)	0.0568 (5)
O3	0.67936 (19)	1.0359 (2)	−0.04189 (9)	0.0647 (6)
H3	0.7767	1.0594	−0.0360	0.097*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0432 (11)	0.0585 (13)	0.0476 (11)	−0.0017 (11)	−0.0011 (10)	0.0074 (12)
C2	0.0401 (10)	0.0499 (12)	0.0420 (10)	−0.0017 (10)	−0.0004 (9)	0.0037 (10)
C3	0.0377 (9)	0.0479 (11)	0.0383 (9)	−0.0040 (10)	0.0045 (9)	0.0014 (9)
C4	0.0310 (9)	0.0733 (15)	0.0399 (10)	0.0022 (11)	0.0015 (9)	0.0018 (11)
C5	0.0352 (10)	0.0824 (17)	0.0441 (11)	−0.0036 (12)	0.0082 (9)	0.0135 (12)
C6	0.0361 (10)	0.0641 (13)	0.0403 (10)	−0.0009 (10)	0.0069 (9)	0.0113 (10)
C7	0.0448 (11)	0.0820 (16)	0.0378 (10)	0.0094 (13)	0.0056 (10)	−0.0024 (11)
C8	0.0484 (12)	0.0904 (19)	0.0455 (11)	−0.0002 (14)	−0.0053 (11)	−0.0075 (13)
C9	0.0384 (11)	0.0781 (16)	0.0486 (11)	−0.0010 (12)	−0.0044 (11)	−0.0014 (12)
C10	0.0381 (11)	0.0629 (14)	0.0481 (11)	0.0058 (11)	0.0048 (10)	0.0028 (11)
C11	0.0356 (10)	0.0507 (12)	0.0418 (10)	−0.0012 (9)	0.0024 (9)	−0.0009 (9)
C12	0.0327 (9)	0.0556 (12)	0.0357 (9)	−0.0045 (9)	0.0031 (8)	0.0033 (10)
C13	0.0574 (14)	0.0724 (15)	0.0386 (10)	−0.0003 (13)	0.0000 (11)	0.0016 (11)
C14	0.0605 (14)	0.0576 (13)	0.0717 (15)	−0.0026 (12)	−0.0018 (14)	−0.0084 (13)
C15	0.0631 (16)	0.0726 (16)	0.0825 (17)	0.0173 (14)	−0.0060 (16)	0.0115 (15)
O1	0.0436 (8)	0.0838 (12)	0.0612 (9)	−0.0014 (9)	−0.0117 (8)	0.0080 (9)
O2	0.0333 (7)	0.0884 (12)	0.0488 (8)	0.0062 (9)	0.0030 (7)	0.0099 (9)
O3	0.0375 (8)	0.1178 (16)	0.0388 (7)	−0.0027 (10)	0.0079 (7)	−0.0008 (10)

Geometric parameters (Å, º) top

C1—O1	1.210 (3)	C8—H8B	0.9700
C1—O2	1.350 (3)	C9—C10	1.530 (3)
C1—C2	1.477 (3)	C9—H9A	0.9700
C2—C3	1.337 (3)	C9—H9B	0.9700
C2—C13	1.499 (3)	C10—C15	1.537 (3)
C3—C12	1.492 (3)	C10—C11	1.557 (3)
C3—C4	1.500 (3)	C10—H10	0.9800
C4—O2	1.445 (2)	C11—C14	1.532 (3)
C4—C5	1.502 (3)	C11—C12	1.563 (3)
C4—H4	0.9800	C12—O3	1.421 (2)
C5—C6	1.536 (3)	C12—H12	0.9800
C5—H5A	0.9700	C13—H13A	0.9600
C5—H5B	0.9700	C13—H13B	0.9600
C6—C7	1.525 (4)	C13—H13C	0.9600
C6—C11	1.557 (3)	C14—H14A	0.9600
C6—H6	0.9800	C14—H14B	0.9600
C7—C8	1.532 (3)	C14—H14C	0.9600
C7—H7A	0.9700	C15—H15A	0.9600
C7—H7B	0.9700	C15—H15B	0.9600
C8—C9	1.521 (3)	C15—H15C	0.9600
C8—H8A	0.9700	O3—H3	0.8200

O1—C1—O2	120.8 (2)	C8—C9—H9B	109.0
O1—C1—C2	129.5 (2)	C10—C9—H9B	109.0
O2—C1—C2	109.71 (19)	H9A—C9—H9B	107.8
C3—C2—C1	107.30 (19)	C9—C10—C15	110.24 (19)
C3—C2—C13	132.62 (19)	C9—C10—C11	112.15 (19)
C1—C2—C13	120.07 (19)	C15—C10—C11	113.4 (2)
C2—C3—C12	132.96 (19)	C9—C10—H10	106.9
C2—C3—C4	109.45 (18)	C15—C10—H10	106.9
C12—C3—C4	117.38 (17)	C11—C10—H10	106.9
O2—C4—C3	104.59 (16)	C14—C11—C6	110.74 (18)
O2—C4—C5	111.93 (18)	C14—C11—C10	110.26 (19)
C3—C4—C5	111.4 (2)	C6—C11—C10	109.67 (16)
O2—C4—H4	109.6	C14—C11—C12	107.52 (16)
C3—C4—H4	109.6	C6—C11—C12	109.39 (17)
C5—C4—H4	109.6	C10—C11—C12	109.22 (17)
C4—C5—C6	109.90 (18)	O3—C12—C3	108.46 (17)
C4—C5—H5A	109.7	O3—C12—C11	112.88 (18)
C6—C5—H5A	109.7	C3—C12—C11	110.02 (16)
C4—C5—H5B	109.7	O3—C12—H12	108.5
C6—C5—H5B	109.7	C3—C12—H12	108.5
H5A—C5—H5B	108.2	C11—C12—H12	108.5
C7—C6—C5	110.9 (2)	C2—C13—H13A	109.5
C7—C6—C11	113.71 (18)	C2—C13—H13B	109.5
C5—C6—C11	111.80 (17)	H13A—C13—H13B	109.5
C7—C6—H6	106.7	C2—C13—H13C	109.5
C5—C6—H6	106.7	H13A—C13—H13C	109.5
C11—C6—H6	106.7	H13B—C13—H13C	109.5
C6—C7—C8	112.3 (2)	C11—C14—H14A	109.5
C6—C7—H7A	109.1	C11—C14—H14B	109.5
C8—C7—H7A	109.1	H14A—C14—H14B	109.5
C6—C7—H7B	109.1	C11—C14—H14C	109.5
C8—C7—H7B	109.1	H14A—C14—H14C	109.5
H7A—C7—H7B	107.9	H14B—C14—H14C	109.5
C9—C8—C7	109.66 (18)	C10—C15—H15A	109.5
C9—C8—H8A	109.7	C10—C15—H15B	109.5
C7—C8—H8A	109.7	H15A—C15—H15B	109.5
C9—C8—H8B	109.7	C10—C15—H15C	109.5
C7—C8—H8B	109.7	H15A—C15—H15C	109.5
H8A—C8—H8B	108.2	H15B—C15—H15C	109.5
C8—C9—C10	112.8 (2)	C1—O2—C4	108.92 (16)
C8—C9—H9A	109.0	C12—O3—H3	109.5
C10—C9—H9A	109.0

O1—C1—C2—C3	−177.7 (3)	C7—C6—C11—C10	50.5 (2)
O2—C1—C2—C3	1.0 (3)	C5—C6—C11—C10	177.0 (2)
O1—C1—C2—C13	1.6 (4)	C7—C6—C11—C12	−69.2 (2)
O2—C1—C2—C13	−179.7 (2)	C5—C6—C11—C12	57.3 (2)
C1—C2—C3—C12	172.8 (2)	C9—C10—C11—C14	−173.30 (18)
C13—C2—C3—C12	−6.4 (4)	C15—C10—C11—C14	−47.6 (3)
C1—C2—C3—C4	−1.6 (3)	C9—C10—C11—C6	−51.1 (2)
C13—C2—C3—C4	179.2 (3)	C15—C10—C11—C6	74.6 (3)
C2—C3—C4—O2	1.6 (3)	C9—C10—C11—C12	68.8 (2)
C12—C3—C4—O2	−173.75 (18)	C15—C10—C11—C12	−165.52 (19)
C2—C3—C4—C5	122.8 (2)	C2—C3—C12—O3	0.9 (3)
C12—C3—C4—C5	−52.6 (3)	C4—C3—C12—O3	174.9 (2)
O2—C4—C5—C6	170.32 (18)	C2—C3—C12—C11	−123.0 (3)
C3—C4—C5—C6	53.6 (3)	C4—C3—C12—C11	51.0 (3)
C4—C5—C6—C7	69.5 (2)	C14—C11—C12—O3	−52.3 (2)
C4—C5—C6—C11	−58.5 (3)	C6—C11—C12—O3	−172.67 (16)
C5—C6—C7—C8	179.21 (18)	C10—C11—C12—O3	67.3 (2)
C11—C6—C7—C8	−53.8 (3)	C14—C11—C12—C3	69.0 (2)
C6—C7—C8—C9	55.2 (3)	C6—C11—C12—C3	−51.4 (2)
C7—C8—C9—C10	−56.9 (3)	C10—C11—C12—C3	−171.41 (18)
C8—C9—C10—C15	−71.1 (3)	O1—C1—O2—C4	178.9 (2)
C8—C9—C10—C11	56.3 (3)	C2—C1—O2—C4	0.1 (3)
C7—C6—C11—C14	172.43 (19)	C3—C4—O2—C1	−1.0 (3)
C5—C6—C11—C14	−61.0 (3)	C5—C4—O2—C1	−121.8 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O1ⁱ	0.82	2.18	2.931 (2)	152

Symmetry code: (i) x+1, y, z.

Experimental details

Crystal data
Chemical formula	C₁₅H₂₂O₃
M_r	250.33
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	293
a, b, c (Å)	8.0141 (16), 9.969 (2), 16.482 (3)
V (Å³)	1316.8 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.60 × 0.60 × 0.30

Data collection
Diffractometer	Rigaku R-AXIS RAPID IP diffractometer
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
T_min, T_max	0.950, 0.975
No. of measured, independent and observed [I > 2σ(I)] reflections	8965, 1744, 1314
R_int	0.061
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.047, 0.107, 0.95
No. of reflections	1744
No. of parameters	168
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.21, −0.20

Computer programs: RAPID-AUTO (Rigaku, 2000), CrystalStructure (Rigaku/MSC, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O1ⁱ	0.82	2.18	2.931 (2)	152

Symmetry code: (i) x+1, y, z.

Acknowledgements

The project was supported by the 985 Project (MUC985) Minzu University of China, and the Major Project for Young Teachers in Minzu University of China CUN10A, together with the "Programme of Introducing Talents of Discipline to Universities" (B08044), and the "Project for Scientific and Technical Achievements in Industrialization", Beijing Education Commission.

References

Fu, K. Z., Yu, N. J., Zhang, Y. & Zhao, Y. M. (2007). Yaoxue Xuebao, 42, 621–624. CAS Google Scholar
Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku (2000). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku/MSC (2000). Crystal Structure. Rigaku/MSC, The Woodlands, Texas, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wang, W. S., Gao, K., Yang, L. & Jia, Z. J. (2000). Planta Med. 66, 189–191. Web of Science CrossRef PubMed CAS Google Scholar