1-(2,6-Dihydr­oxy-4-methoxy­phen­yl)-3-phenyl­propan-1-one

Chantrapromma, S.; Jeerapong, J.; Kruahong, T.; Laphookhieo, S.; Fun, H.-K.

doi:10.1107/S1600536810013590

organic compounds

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ISSN: 2056-9890

Volume 66| Part 5| May 2010| Pages o1120-o1121

https://doi.org/10.1107/S1600536810013590

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1-(2,6-Dihydroxy-4-methoxyphenyl)-3-phenylpropan-1-one¹

Suchada Chantrapromma,^a ^*‡ Jutatip Jeerapong,^b Thongchai Kruahong,^b Surat Laphookhieo ^c and Hoong-Kun Fun ^d §

^aCrystal Materials Research Unit, Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand, ^bDepartment of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science and Technology, Suratthani Rajabhat University, Mueang, Surat Thani 84100, Thailand, ^cNatural Products Research Laboratory, School of Science, Mae Fah Luang University, Muang, Chiang Rai 57100, Thailand, and ^dX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: suchada.c@psu.ac.th

(Received 2 April 2010; accepted 13 April 2010; online 21 April 2010)

The title compound, C₁₆H₁₆O₄, a dihydrochalcone, was isolated from the rhizomes of Etlingera littoralis. The molecule is twisted with a dihedral angle of 71.69 (6)° between the two aromatic rings. The propanone unit makes dihedral angles of 4.07 (6) and 73.56 (7)°, respectively, with the 2,6-dihydroxy-4-methoxyphenyl and phenyl rings. The methoxy group is approximately coplanar with the attached benzene ring with a dihedral angle of 1.74 (10)°. An intramolecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into chains along [201]. A π–π interaction with a centroid–centroid distance of 3.5185 (6) Å is also observed.

Related literature

For details of hydrogen-bond motifs, see: Bernstein et al. (1995 ). For bond-length data, see: Allen et al. (1987 ). For background to dihydrochalcones and their activities, see: Nilsson (1961 ); Nowakowska (2007 ); Portet et al. (2007 ). For Zingiberaceae plants, see: Chuakul & Boonpleng (2003 ); Reanmongkol et al. (2006 ); Sirirugsa (1999 ); Tewtrakul, Subhadhirasakul & Kummee (2003 ); Tewtrakul, Subhadhirasakul, Puripattanavong & Panphadung (2003 ). For a related structure, see: Ng et al. (2005 ). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₆H₁₆O₄
M_r = 272.29
Monoclinic, C c
a = 7.2142 (6) Å
b = 30.522 (2) Å
c = 6.5587 (5) Å
β = 107.267 (2)°
V = 1379.09 (18) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.46 × 0.34 × 0.18 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.958, T_max = 0.983
17744 measured reflections
3044 independent reflections
2940 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.034
wR(F²) = 0.097
S = 1.08
3044 reflections
186 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.40 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H1O2⋯O1	0.82	1.71	2.4576 (11)	150
O4—H1O4⋯O2ⁱ	0.80 (3)	1.90 (3)	2.6920 (10)	175 (3)
Symmetry code: (i) $[x+1, -y, z+{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810013590/is2537sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810013590/is2537Isup2.hkl

checkCIF report

Comment top

Zingiberaceae plants are the ground plants of tropical forests. Many of them are used for food, spices, medicines, dyes, perfume and aesthetics (Sirirugsa, 1999). Secondary metabolites from Zingiberaceae plants have found to be anti-inflammatory (Reanmongkol et al., 2006), HIV-1 protease inhibitory (Tewtrakul, Subhadhirasakul & Kummee, 2003; Tewtrakul, Subhadhirasakul, Puripattanavong & Panphadung, 2003). Etlingera littoralis is one of the Zingiberaceae plants and its decoction of the rhizomes has been used for the treatment of stomachache, carminative and heart tonic (Chuakul & Boonpleng, 2003). As part of our study of chemical constituents and bioactive compounds from the rhizomes of Etlingera littoralis which were collected from Surat Thani province in the southern of Thailand, the title dihydrochalcone, (I), was isolated. Herein we report its crystal structure. The title compound was found to possess antibacterial (Nowakowska, 2007) and antiplasmodial activities (Portet et al., 2007).

The molecule of the title dihydrochalcone (Fig. 1), C₁₆H₁₆O₄, is twisted as the dihedral angle between the 2,6-dihydroxy-4-methoxyphenyl and phenyl rings is 71.69 (6)°. Whereas the 1-propanone unit (C7–C9/O1) makes the dihedral angles of 4.07 (6) and 73.56 (7)° with the C1–C6 benzene and C10–C15 phenyl rings, respectively. The two hydroxy and a methoxy groups are co-planar with the attached benzene ring with the r.m.s. of 0.0078 (1) Å for the ten non H atoms and the torsion angle C16–O3–C3–C2 = -1.66 (15)°. An intramolecular O2—H1O2···O1 hydrogen bond generates an S(6) ring motif (Bernstein et al., 1995) (Fig. 1 and Table 1). The bond distances are of normal values (Allen et al., 1987) and are comparable with the closely related structure (Ng et al., 2005).

In the crystal packing (Fig. 2) , O—H···O hydrogen bonds (Table 1) formed between the two hydroxy groups link the molecules into chains along the [201] direction in which the adjacent chains are in anti-parallel manner. A π–π interaction with Cg1···Cg1 distance of 3.5185 (6) Å was observed (symmetry code x, -y, -1/2+z); Cg1 is the centroid of the C1–C6 benzene ring.

Related literature top

For details of hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For background to dihydrochalcones and their activities, see: Nilsson (1961); Nowakowska (2007); Portet et al. (2007). For Zingiberaceae plants, see: Chuakul & Boonpleng (2003); Reanmongkol et al. (2006); Sirirugsa (1999); Tewtrakul, Subhadhirasakul & Kummee (2003); Tewtrakul, Subhadhirasakul, Puripattanavong & Panphadung (2003). For a related structure, see: Ng et al. (2005). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

Experimental top

The fresh rhizomes of E. littoralis (3.89 kg) were chopped and extracted with 50% CH₂Cl₂-MeOH, over the period of 3 days at room temperature. The extraction was filtered and evaporated to dryness under reduced pressure to give crude extract which was further partitioned with water and CH₂Cl₂ to afford the dichloromethane extract (22.88 g). The portion of dichloromethane extract (11.80 g) was subjected to quick column chromatography (QCC) on silica gel eluting with a gradient of EtOAc–hexane to give thirteen fractions. Fraction F8 (322.4 mg) was washed with 20% CH₂Cl₂-hexane yielding solid which was further separated by column chromatography on silica gel with 70% CH₂Cl₂-hexane to give compound (I) (50.1 mg). Yellow block-shaped single crystals of the compound (I) suitable for X-ray structure determination were obtained from ethyl acetate by slow evaporation at room temperature after a few days, Mp 443 K. The NMR spectral data were consistent with the X-ray structure.

Structure description top

For details of hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For background to dihydrochalcones and their activities, see: Nilsson (1961); Nowakowska (2007); Portet et al. (2007). For Zingiberaceae plants, see: Chuakul & Boonpleng (2003); Reanmongkol et al. (2006); Sirirugsa (1999); Tewtrakul, Subhadhirasakul & Kummee (2003); Tewtrakul, Subhadhirasakul, Puripattanavong & Panphadung (2003). For a related structure, see: Ng et al. (2005). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. The crystal packing of the title compound viewed down the b axis, showing chains running along the [201] direction. Hydrogen bonds are shown as dashed lines.

1-(2,6-Dihydroxy-4-methoxyphenyl)-3-phenylpropan-1-one top

Crystal data top

C₁₆H₁₆O₄	F(000) = 576
M_r = 272.29	D_x = 1.311 Mg m⁻³
Monoclinic, Cc	Melting point: 443 K
Hall symbol: C -2yc	Mo Kα radiation, λ = 0.71073 Å
a = 7.2142 (6) Å	Cell parameters from 3044 reflections
b = 30.522 (2) Å	θ = 2.7–35.0°
c = 6.5587 (5) Å	µ = 0.09 mm⁻¹
β = 107.267 (2)°	T = 100 K
V = 1379.09 (18) Å³	Block, yellow
Z = 4	0.46 × 0.34 × 0.18 mm

Data collection top

Bruker APEX DUO CCD area-detector diffractometer	3044 independent reflections
Radiation source: sealed tube	2940 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
φ and ω scans	θ_max = 35.0°, θ_min = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −11→11
T_min = 0.958, T_max = 0.983	k = −49→48
17744 measured reflections	l = −10→10

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.097	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ²(F_o²) + (0.0648P)² + 0.1812P] where P = (F_o² + 2F_c²)/3
3044 reflections	(Δ/σ)_max = 0.001
186 parameters	Δρ_max = 0.34 e Å⁻³
2 restraints	Δρ_min = −0.40 e Å⁻³

Crystal data top

C₁₆H₁₆O₄	V = 1379.09 (18) Å³
M_r = 272.29	Z = 4
Monoclinic, Cc	Mo Kα radiation
a = 7.2142 (6) Å	µ = 0.09 mm⁻¹
b = 30.522 (2) Å	T = 100 K
c = 6.5587 (5) Å	0.46 × 0.34 × 0.18 mm
β = 107.267 (2)°

Data collection top

Bruker APEX DUO CCD area-detector diffractometer	3044 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	2940 reflections with I > 2σ(I)
T_min = 0.958, T_max = 0.983	R_int = 0.025
17744 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.034	2 restraints
wR(F²) = 0.097	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	Δρ_max = 0.34 e Å⁻³
3044 reflections	Δρ_min = −0.40 e Å⁻³
186 parameters

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

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. 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 > 2sigma(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
O1	0.57929 (10)	0.09273 (3)	0.16110 (12)	0.01772 (14)
O2	0.40256 (10)	0.02283 (2)	0.09183 (12)	0.01659 (14)
H1O2	0.4212	0.0494	0.0997	0.025*
O3	0.76008 (12)	−0.11076 (2)	0.22402 (13)	0.01827 (13)
O4	1.09458 (10)	0.02313 (2)	0.35682 (12)	0.01540 (13)
H1O4	1.186 (4)	0.0088 (8)	0.419 (4)	0.043 (6)*
C1	0.57479 (11)	0.00170 (3)	0.15654 (13)	0.01230 (14)
C2	0.56979 (13)	−0.04392 (3)	0.15433 (14)	0.01400 (15)
H2A	0.4524	−0.0589	0.1102	0.017*
C3	0.74533 (14)	−0.06642 (3)	0.21997 (15)	0.01307 (13)
C4	0.92225 (13)	−0.04409 (3)	0.28721 (14)	0.01272 (14)
H4A	1.0381	−0.0597	0.3298	0.015*
C5	0.92521 (11)	0.00137 (3)	0.29051 (12)	0.01140 (13)
C6	0.75073 (14)	0.02604 (3)	0.22318 (15)	0.01112 (13)
C7	0.74075 (13)	0.07385 (3)	0.21838 (14)	0.01271 (13)
C8	0.91965 (13)	0.10221 (3)	0.27702 (14)	0.01421 (14)
H8A	1.0023	0.0936	0.1911	0.017*
H8B	0.9911	0.0971	0.4255	0.017*
C9	0.87479 (16)	0.15107 (3)	0.24454 (17)	0.01880 (16)
H9A	0.7893	0.1559	0.1013	0.023*
H9B	0.8081	0.1608	0.3448	0.023*
C10	1.05757 (16)	0.17743 (3)	0.27659 (18)	0.01983 (18)
C11	1.1302 (2)	0.20381 (4)	0.4562 (2)	0.0303 (2)
H11A	1.0662	0.2049	0.5601	0.036*
C12	1.2988 (3)	0.22868 (4)	0.4815 (3)	0.0440 (4)
H12A	1.3455	0.2463	0.6013	0.053*
C13	1.3961 (2)	0.22708 (5)	0.3287 (3)	0.0453 (4)
H13A	1.5074	0.2438	0.3455	0.054*
C14	1.3276 (2)	0.20066 (5)	0.1517 (3)	0.0396 (3)
H14A	1.3938	0.1992	0.0499	0.048*
C15	1.15876 (19)	0.17616 (4)	0.1255 (2)	0.0273 (2)
H15A	1.1128	0.1587	0.0049	0.033*
C16	0.58350 (17)	−0.13568 (3)	0.16199 (18)	0.0230 (2)
H16A	0.6136	−0.1664	0.1775	0.034*
H16B	0.5142	−0.1294	0.0157	0.034*
H16C	0.5046	−0.1279	0.2513	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0124 (3)	0.0166 (3)	0.0227 (3)	0.0027 (2)	0.0030 (2)	0.0000 (3)
O2	0.0085 (3)	0.0182 (3)	0.0212 (3)	0.0004 (2)	0.0016 (2)	−0.0017 (2)
O3	0.0201 (3)	0.0120 (3)	0.0216 (3)	−0.0026 (2)	0.0044 (2)	−0.0005 (2)
O4	0.0072 (2)	0.0147 (3)	0.0221 (3)	−0.0008 (2)	0.0010 (2)	0.0007 (2)
C1	0.0087 (3)	0.0161 (3)	0.0118 (3)	−0.0003 (3)	0.0025 (2)	−0.0004 (3)
C2	0.0119 (3)	0.0157 (3)	0.0139 (3)	−0.0030 (3)	0.0030 (3)	−0.0011 (3)
C3	0.0144 (3)	0.0129 (3)	0.0116 (3)	−0.0014 (3)	0.0034 (2)	−0.0004 (3)
C4	0.0111 (3)	0.0132 (3)	0.0134 (3)	0.0002 (3)	0.0029 (2)	0.0002 (3)
C5	0.0089 (3)	0.0135 (3)	0.0114 (3)	−0.0005 (3)	0.0025 (2)	0.0002 (3)
C6	0.0087 (3)	0.0128 (3)	0.0114 (3)	−0.0007 (3)	0.0022 (2)	−0.0004 (3)
C7	0.0117 (3)	0.0137 (3)	0.0124 (3)	0.0003 (3)	0.0032 (2)	−0.0002 (3)
C8	0.0130 (3)	0.0125 (3)	0.0161 (3)	−0.0013 (3)	0.0028 (3)	−0.0007 (3)
C9	0.0179 (4)	0.0126 (3)	0.0242 (4)	0.0011 (3)	0.0036 (3)	−0.0009 (3)
C10	0.0203 (4)	0.0112 (3)	0.0232 (4)	−0.0016 (3)	−0.0010 (3)	0.0012 (3)
C11	0.0361 (6)	0.0168 (4)	0.0293 (5)	−0.0027 (4)	−0.0035 (4)	−0.0040 (4)
C12	0.0459 (8)	0.0190 (5)	0.0472 (8)	−0.0115 (5)	−0.0170 (6)	0.0002 (5)
C13	0.0297 (6)	0.0271 (6)	0.0637 (10)	−0.0136 (5)	−0.0098 (6)	0.0190 (6)
C14	0.0266 (5)	0.0360 (7)	0.0532 (8)	−0.0074 (5)	0.0073 (6)	0.0202 (6)
C15	0.0251 (5)	0.0238 (5)	0.0308 (5)	−0.0043 (4)	0.0052 (4)	0.0054 (4)
C16	0.0263 (5)	0.0178 (4)	0.0227 (4)	−0.0090 (4)	0.0040 (4)	−0.0014 (3)

Geometric parameters (Å, º) top

O1—C7	1.2531 (11)	C8—H8B	0.9700
O2—C1	1.3516 (11)	C9—C10	1.5052 (14)
O2—H1O2	0.8200	C9—H9A	0.9700
O3—C3	1.3574 (11)	C9—H9B	0.9700
O3—C16	1.4349 (13)	C10—C11	1.3943 (15)
O4—C5	1.3445 (10)	C10—C15	1.3951 (17)
O4—H1O4	0.79 (3)	C11—C12	1.401 (2)
C1—C2	1.3928 (13)	C11—H11A	0.9300
C1—C6	1.4230 (12)	C12—C13	1.384 (3)
C2—C3	1.3917 (14)	C12—H12A	0.9300
C2—H2A	0.9300	C13—C14	1.379 (3)
C3—C4	1.3978 (13)	C13—H13A	0.9300
C4—C5	1.3877 (12)	C14—C15	1.3956 (18)
C4—H4A	0.9300	C14—H14A	0.9300
C5—C6	1.4201 (12)	C15—H15A	0.9300
C6—C7	1.4607 (11)	C16—H16A	0.9600
C7—C8	1.5061 (13)	C16—H16B	0.9600
C8—C9	1.5276 (13)	C16—H16C	0.9600
C8—H8A	0.9700

C1—O2—H1O2	109.5	C10—C9—C8	111.21 (8)
C3—O3—C16	117.72 (9)	C10—C9—H9A	109.4
C5—O4—H1O4	115.4 (18)	C8—C9—H9A	109.4
O2—C1—C2	117.08 (8)	C10—C9—H9B	109.4
O2—C1—C6	120.02 (8)	C8—C9—H9B	109.4
C2—C1—C6	122.90 (8)	H9A—C9—H9B	108.0
C3—C2—C1	118.14 (8)	C11—C10—C15	118.14 (11)
C3—C2—H2A	120.9	C11—C10—C9	121.36 (11)
C1—C2—H2A	120.9	C15—C10—C9	120.50 (9)
O3—C3—C2	123.84 (9)	C10—C11—C12	120.52 (15)
O3—C3—C4	114.90 (9)	C10—C11—H11A	119.7
C2—C3—C4	121.26 (7)	C12—C11—H11A	119.7
C5—C4—C3	120.05 (8)	C13—C12—C11	120.27 (14)
C5—C4—H4A	120.0	C13—C12—H12A	119.9
C3—C4—H4A	120.0	C11—C12—H12A	119.9
O4—C5—C4	120.48 (8)	C14—C13—C12	119.88 (13)
O4—C5—C6	118.37 (7)	C14—C13—H13A	120.1
C4—C5—C6	121.15 (8)	C12—C13—H13A	120.1
C5—C6—C1	116.50 (7)	C13—C14—C15	119.88 (16)
C5—C6—C7	124.74 (8)	C13—C14—H14A	120.1
C1—C6—C7	118.76 (8)	C15—C14—H14A	120.1
O1—C7—C6	120.09 (8)	C10—C15—C14	121.29 (13)
O1—C7—C8	117.52 (7)	C10—C15—H15A	119.4
C6—C7—C8	122.38 (8)	C14—C15—H15A	119.4
C7—C8—C9	113.30 (7)	O3—C16—H16A	109.5
C7—C8—H8A	108.9	O3—C16—H16B	109.5
C9—C8—H8A	108.9	H16A—C16—H16B	109.5
C7—C8—H8B	108.9	O3—C16—H16C	109.5
C9—C8—H8B	108.9	H16A—C16—H16C	109.5
H8A—C8—H8B	107.7	H16B—C16—H16C	109.5

O2—C1—C2—C3	179.91 (8)	C5—C6—C7—O1	−178.29 (8)
C6—C1—C2—C3	−0.16 (14)	C1—C6—C7—O1	1.64 (14)
C16—O3—C3—C2	−1.66 (15)	C5—C6—C7—C8	2.74 (15)
C16—O3—C3—C4	178.47 (8)	C1—C6—C7—C8	−177.33 (8)
C1—C2—C3—O3	−179.62 (8)	O1—C7—C8—C9	−3.30 (12)
C1—C2—C3—C4	0.24 (14)	C6—C7—C8—C9	175.70 (8)
O3—C3—C4—C5	−179.79 (8)	C7—C8—C9—C10	−172.32 (8)
C2—C3—C4—C5	0.34 (14)	C8—C9—C10—C11	−108.05 (11)
C3—C4—C5—O4	179.38 (7)	C8—C9—C10—C15	72.21 (12)
C3—C4—C5—C6	−1.01 (14)	C15—C10—C11—C12	0.83 (17)
O4—C5—C6—C1	−179.33 (7)	C9—C10—C11—C12	−178.92 (11)
C4—C5—C6—C1	1.05 (13)	C10—C11—C12—C13	−0.5 (2)
O4—C5—C6—C7	0.60 (14)	C11—C12—C13—C14	−0.4 (2)
C4—C5—C6—C7	−179.02 (8)	C12—C13—C14—C15	1.0 (2)
O2—C1—C6—C5	179.46 (8)	C11—C10—C15—C14	−0.27 (17)
C2—C1—C6—C5	−0.46 (14)	C9—C10—C15—C14	179.47 (11)
O2—C1—C6—C7	−0.47 (13)	C13—C14—C15—C10	−0.6 (2)
C2—C1—C6—C7	179.60 (8)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O1	0.82	1.71	2.4576 (11)	150
O4—H1O4···O2ⁱ	0.80 (3)	1.90 (3)	2.6920 (10)	175 (3)

Symmetry code: (i) x+1, −y, z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₆O₄
M_r	272.29
Crystal system, space group	Monoclinic, Cc
Temperature (K)	100
a, b, c (Å)	7.2142 (6), 30.522 (2), 6.5587 (5)
β (°)	107.267 (2)
V (Å³)	1379.09 (18)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.46 × 0.34 × 0.18

Data collection
Diffractometer	Bruker APEX DUO CCD area-detector
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.958, 0.983
No. of measured, independent and observed [I > 2σ(I)] reflections	17744, 3044, 2940
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.807

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.034, 0.097, 1.08
No. of reflections	3044
No. of parameters	186
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.34, −0.40

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O1	0.82	1.71	2.4576 (11)	150
O4—H1O4···O2ⁱ	0.80 (3)	1.90 (3)	2.6920 (10)	175 (3)

Symmetry code: (i) x+1, −y, z+1/2.

Footnotes

¹This paper is dedicated to Her Royal Highness Princess Maha Chakri Sirindhorn of Thailand on the occasion of her 55th Birthday Anniversary which fell on April 2nd, 2010.

‡Thomson Reuters ResearcherID: A-5085-2009.

§Additional correspondence author, e-mail: hkfun@usm.my. Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

JJ and TK thank the Center of Excellence for Innovation in Chemistry (PERCH-CIC) and the Faculty of Science and Technology, Suratthani Rajabhat University, for financial support. The Natural Products Research Laboratory, School of Science, Mae Fah Luang University, is gratefully acknowledged for laboratory facilities. SC thanks the Prince of Songkla University for financial support. Mr Nawong Boonnak is acknowledged for providing useful information. The authors also thank the Malaysian Government and Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

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