organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Crystal structure of the ethyl 2,4-dihy­dr­oxy-6-methyl­benzoate from Illicium difengpi K.I.B et K.I.M.

aSchool of Mathematics and Physics, Shanghai University of Electric Power, Shanghai, 200090, People's Republic of China, and bDepartment of Pharmacy, Xuhui District Central Hospital, Shanghai, 200031, People's Republic of China
*Correspondence e-mail: zhangningpharm@163.com

Edited by M. Zeller, Purdue University, USA (Received 29 November 2018; accepted 15 December 2018; online 21 December 2018)

The title compound, C10H12O4, was isolated from Illicium difengpi K.I.B et K.I.M. An intra­molecular O—H⋯O hydrogen bond stabilizes the mol­ecular conformation. In the crystal, the compound forms offset slanted stacks of alternating inversion-related mol­ecules along the a axis direction. Inter­molecular O—H⋯O hydrogen bonds link the mol­ecules into double strands parallel to the [101] direction.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Illicium difengpi is a small shrub growing in Guangxi province of China, belonging to the family Illiciaceae (He et al., 2014[He, Y.-Z., Osoro, E. K., Palmer, S. I., Wang, L.-N. & Aboud, N. S. (2014). Chinese Herbal Medicines, 6, 76-79.]). The stem bark of I. difengpi is listed in the Chinese Pharmacopoeia (Pharmacopeia Committee of P. R. of China, 2010[Pharmacopeia Committee of P. R. of China (2010). Pharmacopoeia of People's Republic of China. Beijing: Medical Science and Technology Press.]). It is an important traditional Chinese medicine and is mainly used as a treatment for rheumatic arthritics (Huang et al., 1996[Huang, P., Xi, Z.-M., Zheng, X.-Z., Lai, M.-X. & Zhong, X.-Q. (1996). Acta Pharm. Sin, 31, 278-281.]). The alcoholature of the stem bark of I. difengpi showed outstanding clinical efficacy and pharmacodynamics potency. Previous studies led to the isolation of phenyl­propano­ids, lignans, neolignans and triterpenoids from an extract of I. difengpi (Kouno et al., 1992[Kouno, I., Yanagida, Y., Shimono, S., Shintomi, M. & Yang, C.-S. (1992). Chem. Pharm. Bull. 40, 2461-2464.],1993[Kouno, I., Yanagida, Y., Shimono, S., Shintomi, M., Ito, Y. & Chun-Shu, Y. (1993). Phytochemistry, 32, 1573-1577.]; Wang et al., 1994[Wang, J.-L., Yang, C.-S. & Da, W.-R. (1994). China J. Chin. Mater. Med, 19, 422-423.]; Huang et al., 1997[Huang, P., Nishi, M., Zheng, X.-Z., Lai, M.-X. & Naknishi, T. (1997). Acta Pharm. Sin, 32, 704-707.]; Fang et al., 2010[Fang, L., Du, D., Ding, G.-Z., Si, Y.-K., Yu, S.-S., Liu, Y., Wang, W.-J., Ma, S.-G., Xu, S., Qu, J., Wang, J. M. & Liu, Y. X. (2010). J. Nat. Prod. 73, 818-824.], 2011[Fang, L., Wang, X.-J., Ma, S.-G. & Yu, S.-S. (2011). Acta Pharm. Sin. B, 1, 178-183.]; Chu et al., 2011[Chu, S.-S., Wang, C.-F., Du, S.-S., Liu, S.-L. & Liu, Z.-L. (2011). J. Insect Sci. 11, 152.]; Li et al., 2013[Li, C.-T., Wu, Z.-J. & Chen, W.-S. (2013). Evid-Based Compl. Alt, 2013, 942541.], 2015a[Li, C.-T., Wu, Z.-J. & Chen, W.-S. (2015a). Nat. Prod. Res. 29, 1793-1797.],b[Li, C.-T., Wu, Z.-J. & Chen, W.-S. (2015b). Rec. Nat. Prod, 9, 251-261.]; Pan et al., 2016[Pan, Z.-H., Ning, D.-S., Huang, S.-S., Cheng, L., Xia, M.-W., Peng, L.-Y. & Li, D.-P. (2016). Molecules, 21, 607.]). An ongoing search for bioactive natural products from folk medicine resulted in the isolation of the title compound, which was previously obtained from Umbilicaria esculenta (Miyoshi) Minks (Qiu & Ding, 2001[Qiu, C. & Ding, Y. (2001). China J. Chin. Mater. Med, 26, 608-610.]). The isolation of the title compound from the stem bark of I. difengpi and its crystal structure are reported here.

The mol­ecular structure of the title compound is shown in Fig. 1[link]. The mol­ecular structure contains a methyl group, two hydroxyl groups, and a carboeth­oxy group, which are attached to C2, C4, C6 and C7 of the central benzene ring, respectively. An intra­molecular O3—H3⋯O1 hydrogen bond (Table 1[link]) stabilizes the mol­ecular conformation.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O3—H3⋯O1 0.89 (2) 1.72 (3) 2.4868 (18) 143 (3)
O4—H4⋯O3i 0.96 (3) 1.91 (3) 2.853 (2) 169 (3)
C3—H3A⋯O4ii 0.93 2.54 3.290 (2) 138
Symmetry codes: (i) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]; (ii) [x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}].
[Figure 1]
Figure 1
The mol­ecular structure. Displacement ellipsoids are shown at the 50% probability level.

In the crystal, O4—H4⋯O3i and C3—H3A⋯O4ii hydrogen bonds link the mol­ecules into double strands parallel to the [101] direction. (Fig. 2[link], Table 2[link]). In the solid state, the compound also forms offset slanted stacks of alternating inversion-related mol­ecules along the a-axis direction. (Fig. 3[link])

Table 2
Experimental details

Crystal data
Chemical formula C10H12O4
Mr 196.20
Crystal system, space group Monoclinic, P21/n
Temperature (K) 293
a, b, c (Å) 7.818 (3), 17.017 (6), 8.189 (3)
β (°) 117.459 (4)
V3) 966.7 (6)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.10
Crystal size (mm) 0.15 × 0.13 × 0.08
 
Data collection
Diffractometer Bruker SMART APEX CCD area-detector
Absorption correction Multi-scan (SAINT-Plus; Bruker, 1999[Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.405, 0.968
No. of measured, independent and observed [I > 2σ(I)] reflections 4542, 2097, 1390
Rint 0.037
(sin θ/λ)max−1) 0.649
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.057, 0.172, 1.02
No. of reflections 2097
No. of parameters 135
No. of restraints 2
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.45, −0.23
Computer programs: SMART (Bruker, 1997[Bruker (1997). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]), SAINT-Plus (Bruker, 1999[Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXS97 and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2016 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).
[Figure 2]
Figure 2
The packing of the title compound viewed along the a-axis direction. Dashed lines indicate hydrogen bonds.
[Figure 3]
Figure 3
One of the slanted stacks of inversion-related mol­ecules along the a-axis direction.

A search of the Cambridge Crystallographic Database (version 5.39 with updates up to May 2018; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) indicated that no 2,4-dihy­droxy-6-methyl­benzoic acid ethyl ester has been structurally characterized. Four structurally similar 2,4-dihy­droxy-6-methyl­benzoic acid derivatives have been reported, namely (2-eth­oxy­carbonyl-3,5-di­hydroxy­phen­yl)acetic acid monohydrate (Luck & Mendenhall, 2002[Luck, R. L. & Mendenhall, G. D. (2002). Acta Cryst. E58, o1387-o1388.]), phomozin monohydrate (Mazars et al.,1990[Mazars, C., Rossignol, M. P., Auriol, P. & Klaebe, A. (1990). Phytochemistry, 29, 3441-3444.]), 2,3-dimethyl-3-(O-orsellino­yl)lactic acid monohydrate (Declercq et al.,1991[Declercq, J.-P., Klaebe, A., Rossignol, M. & Mazars, C. (1991). Acta Cryst. C47, 470-472.]) and 2,3,4,5-tetra­hydroxy­pentyl 4,6-dihy­droxy-2,3-di­methyl­benzoate (Talontsi et al., 2012[Talontsi, F. M., Nwemeguela Kenla, T. J., Dittrich, B., Douanla-Meli, C. & Laatsch, H. (2012). Planta Med. 78, 1020-1023.]).

Synthesis and crystallization

The stem bark of Illicium difengpi (5.0 kg), which was purchased from Caitongde Pharmacy, Shanghai, China, was powdered and extracted three times with aqueous ethanol (ethanol/water 8:2) under reflux. The solvent was then evaporated under reduced pressure to obtain a dry residue (150 g). The residue was suspended in water (2 L) and extracted successively with petroleum ether (3 × 2 L), EtOAc (3 × 2 L) and BuOH (3 × 2 L), affording 5 g, 70 g, and 40 g, respectively, of each dried fraction. The EtOAc fraction was subjected to silica gel column chromatography using gradient elution (CH2Cl2/CH3OH, 200:1 to 2:1, v/v) to give four main fractions (Fr.1-1–Fr.1-4), of which Fr.1-2 was purified by successive silica gel column chromatography (CH2Cl2/CH3OH, 100:1→20:1); 2,4-dihy­droxy-6-methyl­benzoic acid ethyl ester (30 mg) was obtained from the fraction eluted by CH2Cl2/CH3OH (40:1). Single crystals suitable for X-ray diffraction analysis were obtained by slow evaporation from acetone solution after two weeks at room temperature.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Structural data


Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART (Bruker, 1997); data reduction: SAINT-Plus (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010).

Ethyl 2,4-dihydroxy-6-methylbenzoate top
Crystal data top
C10H12O4F(000) = 416
Mr = 196.20Dx = 1.348 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 7.818 (3) ÅCell parameters from 878 reflections
b = 17.017 (6) Åθ = 2.4–26.4°
c = 8.189 (3) ŵ = 0.10 mm1
β = 117.459 (4)°T = 293 K
V = 966.7 (6) Å3Sheet, colorless
Z = 40.15 × 0.13 × 0.08 mm
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
1390 reflections with I > 2σ(I)
phi and ω scansRint = 0.037
Absorption correction: multi-scan
(SAINT-Plus; Bruker, 1999)
θmax = 27.5°, θmin = 2.4°
Tmin = 0.405, Tmax = 0.968h = 510
4542 measured reflectionsk = 2122
2097 independent reflectionsl = 108
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.057Hydrogen site location: mixed
wR(F2) = 0.172H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.1019P)2]
where P = (Fo2 + 2Fc2)/3
2097 reflections(Δ/σ)max < 0.001
135 parametersΔρmax = 0.45 e Å3
2 restraintsΔρmin = 0.23 e Å3
Special details top

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

Refinement. The positions of hydroxyl H atoms attached to O3 and O4 were refined. All other H atoms were positioned geometrically and treated as riding atoms: C—H = 0.93–0.97 Å. Uiso(H) were set to 1.5Ueq(C/O) for CH3 and OH, and to 1.2Ueq(C) for CH2 and aromatic C—H.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.0021 (2)0.46363 (7)0.27773 (18)0.0663 (5)
O20.11562 (18)0.57656 (6)0.13811 (16)0.0529 (4)
O30.1367 (2)0.33529 (7)0.13142 (19)0.0679 (5)
H30.050 (4)0.3664 (16)0.216 (3)0.102*
O40.6778 (2)0.32885 (8)0.44828 (18)0.0718 (5)
H40.648 (4)0.2753 (16)0.410 (4)0.108*
C10.2660 (2)0.45967 (8)0.0181 (2)0.0420 (4)
C20.2682 (2)0.37634 (9)0.0131 (2)0.0484 (4)
C30.4047 (3)0.33288 (9)0.1552 (3)0.0551 (5)
H3A0.4036370.2783120.1487120.066*
C40.5412 (3)0.37051 (10)0.3052 (2)0.0524 (5)
C50.5453 (3)0.45134 (10)0.3168 (2)0.0525 (5)
H50.6405220.4756440.4206320.063*
C60.4098 (2)0.49723 (9)0.1763 (2)0.0450 (4)
C70.1165 (2)0.49885 (9)0.1435 (2)0.0450 (4)
C80.0274 (3)0.61634 (11)0.3005 (3)0.0612 (5)
H8A0.1562710.6009670.3241300.073*
H8B0.0103410.6028900.4072050.073*
C90.0009 (4)0.70282 (12)0.2630 (3)0.0802 (7)
H9A0.0157840.7152820.1569110.120*
H9B0.0918980.7313000.3675760.120*
H9C0.1286380.7172790.2405240.120*
C100.4251 (3)0.58478 (9)0.2029 (3)0.0592 (5)
H10A0.5357260.5970630.3172800.089*
H10B0.3109700.6042870.2051700.089*
H10C0.4383650.6089150.1034190.089*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0702 (9)0.0471 (7)0.0545 (8)0.0021 (6)0.0056 (7)0.0024 (5)
O20.0591 (8)0.0349 (6)0.0567 (8)0.0057 (5)0.0198 (6)0.0033 (5)
O30.0783 (10)0.0327 (6)0.0659 (9)0.0050 (6)0.0105 (7)0.0064 (5)
O40.0743 (10)0.0545 (8)0.0646 (9)0.0156 (7)0.0131 (8)0.0103 (6)
C10.0470 (9)0.0329 (8)0.0473 (9)0.0001 (6)0.0228 (8)0.0009 (6)
C20.0547 (10)0.0351 (8)0.0517 (10)0.0036 (7)0.0214 (8)0.0036 (7)
C30.0657 (12)0.0326 (8)0.0659 (11)0.0043 (8)0.0294 (10)0.0027 (8)
C40.0542 (10)0.0455 (9)0.0558 (10)0.0095 (8)0.0238 (9)0.0080 (8)
C50.0501 (10)0.0517 (10)0.0479 (10)0.0036 (7)0.0159 (8)0.0053 (7)
C60.0497 (9)0.0377 (8)0.0484 (9)0.0032 (7)0.0234 (8)0.0029 (7)
C70.0496 (9)0.0357 (8)0.0485 (9)0.0018 (7)0.0217 (8)0.0015 (7)
C80.0674 (12)0.0505 (10)0.0580 (11)0.0125 (9)0.0223 (10)0.0125 (8)
C90.0965 (17)0.0464 (11)0.0998 (17)0.0137 (10)0.0471 (14)0.0177 (10)
C100.0657 (12)0.0390 (9)0.0612 (11)0.0087 (8)0.0192 (10)0.0093 (8)
Geometric parameters (Å, º) top
O1—C71.220 (2)C4—C51.378 (3)
O2—C71.323 (2)C5—C61.390 (2)
O2—C81.451 (2)C5—H50.9300
O3—C21.3502 (19)C6—C101.502 (2)
O3—H30.89 (2)C8—C91.499 (3)
O4—C41.365 (2)C8—H8A0.9700
O4—H40.96 (3)C8—H8B0.9700
C1—C61.417 (2)C9—H9A0.9600
C1—C21.419 (2)C9—H9B0.9600
C1—C71.461 (2)C9—H9C0.9600
C2—C31.377 (2)C10—H10A0.9600
C3—C41.359 (2)C10—H10B0.9600
C3—H3A0.9300C10—H10C0.9600
C7—O2—C8116.70 (13)O1—C7—O2120.51 (15)
C2—O3—H3112.1 (18)O1—C7—C1123.39 (15)
C4—O4—H4103.7 (17)O2—C7—C1116.10 (13)
C6—C1—C2117.54 (14)O2—C8—C9106.95 (15)
C6—C1—C7126.02 (14)O2—C8—H8A110.3
C2—C1—C7116.42 (14)C9—C8—H8A110.3
O3—C2—C3116.31 (14)O2—C8—H8B110.3
O3—C2—C1121.87 (14)C9—C8—H8B110.3
C3—C2—C1121.82 (15)H8A—C8—H8B108.6
C4—C3—C2119.36 (15)C8—C9—H9A109.5
C4—C3—H3A120.3C8—C9—H9B109.5
C2—C3—H3A120.3H9A—C9—H9B109.5
C3—C4—O4120.56 (15)C8—C9—H9C109.5
C3—C4—C5121.07 (15)H9A—C9—H9C109.5
O4—C4—C5118.36 (16)H9B—C9—H9C109.5
C4—C5—C6121.27 (16)C6—C10—H10A109.5
C4—C5—H5119.4C6—C10—H10B109.5
C6—C5—H5119.4H10A—C10—H10B109.5
C5—C6—C1118.93 (15)C6—C10—H10C109.5
C5—C6—C10117.23 (15)H10A—C10—H10C109.5
C1—C6—C10123.84 (14)H10B—C10—H10C109.5
C6—C1—C2—O3179.79 (15)C2—C1—C6—C50.4 (2)
C7—C1—C2—O31.4 (2)C7—C1—C6—C5178.29 (16)
C6—C1—C2—C30.3 (2)C2—C1—C6—C10179.25 (15)
C7—C1—C2—C3178.47 (16)C7—C1—C6—C102.1 (3)
O3—C2—C3—C4179.87 (17)C8—O2—C7—O12.1 (2)
C1—C2—C3—C40.3 (3)C8—O2—C7—C1177.74 (14)
C2—C3—C4—O4179.75 (17)C6—C1—C7—O1178.68 (16)
C2—C3—C4—C50.2 (3)C2—C1—C7—O10.0 (2)
C3—C4—C5—C60.3 (3)C6—C1—C7—O21.1 (2)
O4—C4—C5—C6179.68 (16)C2—C1—C7—O2179.83 (14)
C4—C5—C6—C10.4 (2)C7—O2—C8—C9179.38 (14)
C4—C5—C6—C10179.29 (16)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3···O10.89 (2)1.72 (3)2.4868 (18)143 (3)
O4—H4···O3i0.96 (3)1.91 (3)2.853 (2)169 (3)
C3—H3A···O4ii0.932.543.290 (2)138
Symmetry codes: (i) x+1/2, y+1/2, z+1/2; (ii) x1/2, y+1/2, z1/2.
 

Acknowledgements

The authors thank Professor Zhenxia Chen (Department of Chemistry, Fudan University, Shanghai) for the structure analysis.

Funding information

Funding for this research was provided by: Research Project of Xuhui District Central Hospital (award No. 201706).

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