4-Hy­droxy-3-[(4-hy­droxy-2-oxo-2H-3-chromen­yl)(3-thien­yl)meth­yl]-2H-chromen-2-one

Asad, M.; Oo, C.-W.; Osman, H.; Rosli, M.M.; Fun, H.-K.

doi:10.1107/S1600536811011676

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 5| May 2011| Pages o1037-o1038

doi:10.1107/S1600536811011676

Open

access

4-Hydroxy-3-[(4-hydroxy-2-oxo-2H-3-chromenyl)(3-thienyl)methyl]-2H-chromen-2-one

Mohammad Asad,^a Chuan-Wei Oo,^a ‡ Hasnah Osman,^a Mohd Mustaqim Rosli ^b and Hoong-Kun Fun ^b ^*§

^aSchool of Chemical Sciences, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^bX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 16 March 2011; accepted 29 March 2011; online 7 April 2011)

The whole molecule of the title compound, C₂₃H₁₄O₆S, is disordered over two sets of sites with refined occupancies of 0.8733 (12):0.1267 (12). The dihedral angle between the mean planes through the chromene ring systems is 56.31 (5) and 55.2 (3)° for the major and minor components, respectively. In both components, a pair of intramolecular O—H⋯O interactions generate rings of S(8) graph-set motif. In the crystal, the molecules are linked by intermolecular C—H⋯O interactions, forming chains along the b axis. The structure is further stabilized by π–π interactions with centroid–centroid distances of 3.594 (2) and 3.608 (5) Å.

Related literature

For the biological activity of 4-hydroxycoumarins, see: Abdelhafez et al. (2010 ); Huang et al. (2010 ); Jacquot et al. (2001 ); Kokil et al. (2010 ); Siddiqui & Asad (2010 ); Skulnick et al. (1997 ); Sullivan et al. (1943 ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ).

Experimental

Crystal data

C₂₃H₁₄O₆S
M_r = 418.40
Monoclinic, P 2₁ /c
a = 7.8225 (2) Å
b = 8.9426 (2) Å
c = 27.1317 (6) Å
β = 100.679 (1)°
V = 1865.09 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.22 mm⁻¹
T = 297 K
0.49 × 0.44 × 0.16 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.902, T_max = 0.966
20839 measured reflections
5420 independent reflections
3497 reflections with I > 2σ(I)
R_int = 0.031

Refinement

R[F² > 2σ(F²)] = 0.044
wR(F²) = 0.106
S = 1.02
5420 reflections
524 parameters
252 restraints
H-atom parameters constrained
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3B⋯O4	0.82	1.89	2.7049 (19)	180
O6—H6B⋯O5	0.82	1.79	2.612 (2)	179
C21—H21A⋯O4ⁱ	0.93	2.56	3.475 (8)	168
O3X—H3XB⋯O4X	0.82	1.86	2.682 (15)	178
O6X—H6XB⋯O5X	0.82	1.69	2.49 (2)	168
C23X—H23B⋯O3Xⁱ	0.93	2.53	3.31 (5)	142
Symmetry code: (i) $[-x+2, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

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: 10.1107/S1600536811011676/rz2575sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811011676/rz2575Isup2.hkl

checkCIF report

Comment top

The colourless crystalline bis 4-hydroxycoumarins are obtained from the condensation of coumarin and aldehyde derivatives (Sullivan et al., 1943). A large number of structurally novel 4-hydroxycoumarin derivatives have exhibited estrogenic activity on MCF-7 breast carcinoma cells (Jacquot et al., 2001) and possess several types of biological activities such as antifungal (Kokil et al., 2010), anticoagulant (Abdelhafez et al., 2010) anticancer (Huang et al., 2010), anti-HIV (Skulnick et al., 1997), antibacterial and anti-inflammatory (Siddiqui & Asad, 2010) activities.

In the title compound (Fig. 1), the whole molecule is disordered over two orientations with refined site occupancies of 0.873 (1):0.127 (1). The chromene ring systems are almost planar, with maximum deviation of 0.099 (3) Å for atom C9A (major component, Fig. 2) and 0.12 (2) Å for atom C11X (minor component, Fig. 3). The dihedral angles they form are 56.31 (5) and 55.2 (3)° for the major and minor components, respectively. Two pairs of intramolecular hydrogen bonds, O3—H3B···O4, O6—H6B···O5 (major component) and O3X—H3XB···O4X, O6X—H6XB···O5X (minor component), generate rings of S(8) graph-set motifs (Table 1; Bernstein et al., 1995). In the crystal packing, intermolecular C—H···O hydrogen interactions (Table 1) link the molecules into chains along the b axis (Fig. 4). π—π stacking interactions with centroid-to-centroid distances of 3.594 (2) (major component) and 3.608 (5) Å (minor component) are also observed.

Related literature top

For the biological activity of 4-hydroxycoumarins, see: Abdelhafez et al. (2010); Huang et al. (2010); Jacquot et al. (2001); Kokil et al. (2010); Siddiqui & Asad (2010); Skulnick et al. (1997); Sullivan et al. (1943). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Experimental top

To a well-stirred solution of 4-hydroxycoumarin (6.17 mmol, 1.0 g) in ethanol (10 ml) containing two drops of acetic acid, thiophene-3-carboxaldehyde (3.1 mmol, 0.345 g) was added. The reaction mixture was stirred at room temperature for 8 hr. The completion of the reaction was monitored by TLC. After the reaction was completed, the crystallized solid was separated out, filtered, washed with ethanol and dried. The isolated product was further purified by recrystallization from a chloroform / methanol mixture (1:1 v/v) to give the pure title compound in 70% yield.

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 showing a whole molecule disordered over two orientations.
	Fig. 2. The molecular structure of the major component of the title compund, showing 30% probability displacement ellipsoids. Intramolecular hydrogen bonds are shown as dashed lines.
	Fig. 3. The molecular structure of the minor component of the title compund, showing 30% probability displacement ellipsoids. Intramolecular hydrogen bonds are shown as dashed lines.
	Fig. 4. The crystal packing of the title compound viewed along the c axis. H atoms not involved in the hydrogen bonding interactions (dashed lines) are omitted for clarity. Only the major component of disorder is shown.

4-Hydroxy-3-[(4-hydroxy-2-oxo-2H-3-chromenyl)(3-thienyl)methyl]- 2H-chromen-2-one top

Crystal data top

C₂₃H₁₄O₆S	F(000) = 864
M_r = 418.40	D_x = 1.490 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5379 reflections
a = 7.8225 (2) Å	θ = 2.4–26.0°
b = 8.9426 (2) Å	µ = 0.22 mm⁻¹
c = 27.1317 (6) Å	T = 297 K
β = 100.679 (1)°	Plate, colourless
V = 1865.09 (8) Å³	0.49 × 0.44 × 0.16 mm
Z = 4

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	5420 independent reflections
Radiation source: fine-focus sealed tube	3497 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.031
ϕ and ω scans	θ_max = 30.0°, θ_min = 1.5°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −11→9
T_min = 0.902, T_max = 0.966	k = −12→12
20839 measured reflections	l = −36→38

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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.106	H-atom parameters constrained
S = 1.02	w = 1/[σ²(F_o²) + (0.0409P)² + 0.2504P] where P = (F_o² + 2F_c²)/3
5420 reflections	(Δ/σ)_max = 0.001
524 parameters	Δρ_max = 0.17 e Å⁻³
252 restraints	Δρ_min = −0.21 e Å⁻³

Crystal data top

C₂₃H₁₄O₆S	V = 1865.09 (8) Å³
M_r = 418.40	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 7.8225 (2) Å	µ = 0.22 mm⁻¹
b = 8.9426 (2) Å	T = 297 K
c = 27.1317 (6) Å	0.49 × 0.44 × 0.16 mm
β = 100.679 (1)°

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	5420 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	3497 reflections with I > 2σ(I)
T_min = 0.902, T_max = 0.966	R_int = 0.031
20839 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.044	252 restraints
wR(F²) = 0.106	H-atom parameters constrained
S = 1.02	Δρ_max = 0.17 e Å⁻³
5420 reflections	Δρ_min = −0.21 e Å⁻³
524 parameters

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. 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	Occ. (<1)
S1	1.45953 (7)	−0.16107 (8)	0.88120 (2)	0.06222 (18)	0.8733 (12)
O1	0.84520 (16)	0.13801 (13)	0.97160 (4)	0.0513 (3)	0.8733 (12)
O2	0.76016 (19)	0.09511 (15)	0.72666 (5)	0.0575 (3)	0.8733 (12)
O3	0.9259 (3)	0.42341 (16)	0.85963 (6)	0.0587 (5)	0.8733 (12)
H3B	0.9165	0.3803	0.8326	0.088*	0.8733 (12)
O4	0.89510 (17)	0.28109 (14)	0.77045 (4)	0.0553 (3)	0.8733 (12)
O5	0.91759 (18)	−0.05801 (15)	0.93159 (5)	0.0536 (3)	0.8733 (12)
O6	0.8790 (3)	−0.19519 (16)	0.84525 (7)	0.0568 (5)	0.8733 (12)
H6B	0.8911	−0.1515	0.8722	0.085*	0.8733 (12)
C1	0.9078 (6)	0.0795 (4)	0.93266 (16)	0.0437 (6)	0.8733 (12)
C2	0.8154 (3)	0.2889 (2)	0.97464 (11)	0.0454 (5)	0.8733 (12)
C3	0.7596 (4)	0.3388 (4)	1.01761 (10)	0.0595 (7)	0.8733 (12)
H3A	0.7469	0.2730	1.0432	0.071*	0.8733 (12)
C4	0.7237 (4)	0.4894 (4)	1.02097 (11)	0.0656 (7)	0.8733 (12)
H4A	0.6850	0.5251	1.0492	0.079*	0.8733 (12)
C5	0.7441 (4)	0.5881 (3)	0.98318 (13)	0.0642 (7)	0.8733 (12)
H5A	0.7203	0.6892	0.9864	0.077*	0.8733 (12)
C6	0.7992 (6)	0.5377 (3)	0.94110 (12)	0.0554 (6)	0.8733 (12)
H6A	0.8108	0.6040	0.9155	0.066*	0.8733 (12)
C7	0.8381 (4)	0.3853 (3)	0.93660 (9)	0.0428 (5)	0.8733 (12)
C8	0.9078 (2)	0.32467 (17)	0.89533 (6)	0.0420 (4)	0.8733 (12)
C9	0.9528 (4)	0.1773 (2)	0.89474 (9)	0.0378 (4)	0.8733 (12)
C10	1.0443 (4)	0.1109 (4)	0.85510 (13)	0.0396 (8)	0.8733 (12)
H10A	1.0938	0.1980	0.8409	0.048*	0.8733 (12)
C11	0.9188 (6)	0.0448 (3)	0.81078 (11)	0.0407 (6)	0.8733 (12)
C12	0.8608 (3)	0.1469 (3)	0.76989 (8)	0.0461 (5)	0.8733 (12)
C13	0.7010 (9)	−0.0501 (5)	0.72286 (15)	0.0534 (7)	0.8733 (12)
C14	0.5957 (4)	−0.0905 (4)	0.67758 (12)	0.0706 (8)	0.8733 (12)
H14A	0.5711	−0.0229	0.6512	0.085*	0.8733 (12)
C15	0.5291 (6)	−0.2335 (5)	0.67314 (16)	0.0771 (12)	0.8733 (12)
H15A	0.4580	−0.2631	0.6434	0.093*	0.8733 (12)
C16	0.5671 (5)	−0.3337 (4)	0.71256 (16)	0.0723 (9)	0.8733 (12)
H16A	0.5216	−0.4300	0.7088	0.087*	0.8733 (12)
C17	0.6707 (3)	−0.2930 (3)	0.75702 (11)	0.0623 (6)	0.8733 (12)
H17A	0.6953	−0.3614	0.7832	0.075*	0.8733 (12)
C18	0.7395 (4)	−0.1476 (3)	0.76278 (10)	0.0497 (6)	0.8733 (12)
C19	0.8497 (3)	−0.0960 (2)	0.80817 (8)	0.0447 (4)	0.8733 (12)
C20	1.2020 (10)	0.0152 (9)	0.8759 (4)	0.0407 (7)	0.8733 (12)
C21	1.2656 (6)	−0.0971 (7)	0.8509 (3)	0.0486 (12)	0.8733 (12)
H21A	1.2083	−0.1347	0.8203	0.058*	0.8733 (12)
C22	1.4673 (6)	−0.0292 (5)	0.93173 (17)	0.0635 (9)	0.8733 (12)
H22A	1.5562	−0.0180	0.9594	0.076*	0.8733 (12)
C23	1.3173 (5)	0.0507 (4)	0.92124 (15)	0.0470 (9)	0.8733 (12)
H23A	1.2913	0.1249	0.9427	0.056*	0.8733 (12)
S1X	1.4837 (13)	−0.0494 (11)	0.9255 (3)	0.06222 (18)	0.1267 (12)
O1X	0.7724 (12)	−0.2372 (9)	0.8067 (3)	0.062 (2)	0.1267 (12)
O2X	0.8652 (14)	0.4728 (9)	0.8836 (4)	0.062 (2)	0.1267 (12)
O3X	0.8690 (18)	0.1683 (14)	0.7452 (5)	0.072 (4)	0.1267 (12)
H3XB	0.8894	0.2340	0.7666	0.107*	0.1267 (12)
O4X	0.9408 (13)	0.3872 (9)	0.8135 (3)	0.063 (2)	0.1267 (12)
O5X	0.9168 (13)	−0.1677 (9)	0.8805 (4)	0.057 (2)	0.1267 (12)
O6X	0.921 (3)	0.041 (2)	0.9416 (9)	0.060 (5)	0.1267 (12)
H6XB	0.9180	−0.0187	0.9186	0.089*	0.1267 (12)
C1X	0.867 (2)	−0.1342 (16)	0.8351 (5)	0.044 (3)	0.1267 (12)
C2X	0.708 (2)	−0.205 (2)	0.7575 (5)	0.041 (3)	0.1267 (12)
C3X	0.612 (4)	−0.319 (2)	0.7318 (8)	0.067 (5)	0.1267 (12)
H3XA	0.5931	−0.4090	0.7469	0.081*	0.1267 (12)
C4X	0.547 (4)	−0.289 (2)	0.6821 (8)	0.063 (6)	0.1267 (12)
H4XA	0.4900	−0.3648	0.6620	0.075*	0.1267 (12)
C5X	0.564 (3)	−0.150 (2)	0.6611 (7)	0.062 (4)	0.1267 (12)
H5XA	0.5047	−0.1309	0.6287	0.074*	0.1267 (12)
C6X	0.662 (2)	−0.041 (2)	0.6862 (7)	0.057 (4)	0.1267 (12)
H6XA	0.6848	0.0477	0.6706	0.068*	0.1267 (12)
C7X	0.730 (6)	−0.067 (3)	0.7375 (9)	0.053 (5)	0.1267 (12)
C8X	0.8470 (16)	0.0409 (14)	0.7668 (4)	0.051 (3)	0.1267 (12)
C9X	0.903 (4)	0.007 (2)	0.8152 (6)	0.044 (4)	0.1267 (12)
C10X	1.036 (3)	0.109 (2)	0.8465 (9)	0.035 (3)	0.1267 (12)
H10B	1.0791	0.1734	0.8222	0.042*	0.1267 (12)
C11X	0.964 (3)	0.2153 (14)	0.8809 (6)	0.044 (3)	0.1267 (12)
C12X	0.924 (2)	0.3609 (12)	0.8574 (5)	0.047 (3)	0.1267 (12)
C13X	0.829 (3)	0.4443 (15)	0.9315 (6)	0.038 (3)	0.1267 (12)
C14X	0.774 (4)	0.565 (2)	0.9559 (8)	0.053 (5)	0.1267 (12)
H14B	0.7633	0.6592	0.9412	0.064*	0.1267 (12)
C15X	0.737 (3)	0.5410 (17)	1.0020 (8)	0.054 (6)	0.1267 (12)
H15B	0.7079	0.6225	1.0200	0.065*	0.1267 (12)
C16X	0.741 (3)	0.4021 (18)	1.0232 (7)	0.062 (6)	0.1267 (12)
H16B	0.7078	0.3873	1.0540	0.074*	0.1267 (12)
C17X	0.796 (3)	0.2868 (17)	0.9977 (6)	0.047 (4)	0.1267 (12)
H17B	0.8025	0.1920	1.0120	0.057*	0.1267 (12)
C18X	0.8430 (18)	0.3042 (14)	0.9506 (6)	0.037 (3)	0.1267 (12)
C19X	0.9143 (15)	0.1805 (13)	0.9233 (5)	0.042 (2)	0.1267 (12)
C20X	1.196 (7)	0.025 (7)	0.873 (3)	0.0407 (7)	0.1267 (12)
C21X	1.319 (3)	0.076 (3)	0.9116 (10)	0.037 (4)	0.1267 (12)
H21B	1.3146	0.1672	0.9278	0.044*	0.1267 (12)
C22X	1.411 (2)	−0.149 (2)	0.8693 (7)	0.0635 (9)	0.1267 (12)
H22B	1.4762	−0.2128	0.8532	0.076*	0.1267 (12)
C23X	1.242 (4)	−0.114 (5)	0.8543 (18)	0.047 (6)	0.1267 (12)
H23B	1.1634	−0.1750	0.8336	0.057*	0.1267 (12)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0455 (3)	0.0719 (3)	0.0698 (4)	0.0188 (3)	0.0120 (2)	0.0105 (3)
O1	0.0552 (8)	0.0543 (7)	0.0469 (7)	−0.0024 (6)	0.0156 (6)	0.0068 (5)
O2	0.0571 (8)	0.0671 (8)	0.0436 (7)	0.0022 (7)	−0.0034 (6)	−0.0004 (6)
O3	0.0849 (12)	0.0401 (8)	0.0535 (9)	0.0056 (10)	0.0192 (8)	0.0106 (8)
O4	0.0653 (9)	0.0515 (7)	0.0476 (7)	−0.0016 (6)	0.0069 (6)	0.0115 (6)
O5	0.0626 (9)	0.0421 (6)	0.0557 (8)	−0.0001 (7)	0.0100 (6)	0.0122 (6)
O6	0.0620 (10)	0.0443 (9)	0.0625 (11)	−0.0074 (9)	0.0068 (8)	0.0063 (8)
C1	0.0369 (11)	0.0434 (16)	0.0490 (15)	−0.0004 (13)	0.0036 (10)	0.0047 (12)
C2	0.0351 (13)	0.0552 (11)	0.0458 (19)	−0.0018 (9)	0.0069 (14)	−0.0021 (12)
C3	0.0526 (15)	0.074 (2)	0.0549 (15)	−0.0058 (18)	0.0174 (11)	−0.0067 (15)
C4	0.0537 (14)	0.081 (2)	0.0664 (17)	−0.0012 (18)	0.0211 (13)	−0.0181 (16)
C5	0.0624 (17)	0.0629 (16)	0.066 (2)	0.0120 (15)	0.0087 (16)	−0.0126 (14)
C6	0.0563 (16)	0.0508 (15)	0.058 (2)	0.0082 (13)	0.0068 (16)	−0.0037 (13)
C7	0.0374 (10)	0.0428 (15)	0.0464 (12)	0.0009 (16)	0.0029 (9)	0.0018 (11)
C8	0.0404 (9)	0.0421 (8)	0.0422 (9)	0.0003 (7)	0.0044 (7)	0.0050 (7)
C9	0.0321 (10)	0.0401 (11)	0.0405 (13)	−0.0009 (10)	0.0048 (9)	0.0053 (9)
C10	0.0350 (14)	0.0411 (13)	0.0414 (15)	−0.0036 (9)	0.0034 (10)	0.0042 (11)
C11	0.0325 (14)	0.0473 (12)	0.0423 (12)	−0.0031 (10)	0.0067 (11)	0.0021 (9)
C12	0.0412 (10)	0.0550 (13)	0.0421 (12)	0.0008 (9)	0.0077 (10)	0.0008 (10)
C13	0.041 (2)	0.0665 (15)	0.051 (2)	0.0010 (14)	0.0069 (18)	−0.0136 (14)
C14	0.051 (2)	0.093 (3)	0.0623 (18)	0.0062 (17)	−0.0046 (14)	−0.0223 (15)
C15	0.0396 (16)	0.106 (3)	0.083 (2)	−0.004 (2)	0.0024 (15)	−0.046 (2)
C16	0.046 (2)	0.0877 (18)	0.088 (3)	−0.0199 (13)	0.023 (2)	−0.0410 (19)
C17	0.0452 (15)	0.0625 (14)	0.0822 (18)	−0.0150 (11)	0.0201 (12)	−0.0222 (13)
C18	0.0351 (14)	0.0551 (16)	0.0600 (14)	−0.0031 (12)	0.0118 (10)	−0.0122 (12)
C19	0.0356 (10)	0.0474 (10)	0.0515 (11)	0.0002 (8)	0.0091 (9)	0.0009 (9)
C20	0.0356 (10)	0.0425 (15)	0.0438 (15)	−0.0002 (7)	0.0070 (7)	0.0053 (14)
C21	0.0420 (16)	0.0546 (18)	0.0502 (16)	0.0024 (13)	0.0109 (14)	0.0014 (16)
C22	0.0570 (19)	0.069 (2)	0.0671 (18)	−0.0021 (13)	0.0172 (12)	−0.0084 (12)
C23	0.0445 (13)	0.0495 (16)	0.0445 (17)	−0.0007 (11)	0.0016 (12)	0.0047 (14)
S1X	0.0455 (3)	0.0719 (3)	0.0698 (4)	0.0188 (3)	0.0120 (2)	0.0105 (3)
O1X	0.063 (6)	0.060 (5)	0.062 (5)	−0.018 (4)	0.008 (4)	−0.010 (4)
O2X	0.076 (7)	0.044 (5)	0.070 (6)	0.015 (4)	0.025 (5)	0.003 (4)
O3X	0.067 (8)	0.079 (7)	0.066 (8)	0.017 (6)	0.002 (7)	0.027 (7)
O4X	0.073 (6)	0.048 (5)	0.069 (5)	−0.004 (4)	0.018 (5)	0.011 (4)
O5X	0.064 (6)	0.045 (5)	0.057 (5)	−0.001 (4)	−0.003 (5)	0.008 (4)
O6X	0.064 (10)	0.049 (8)	0.074 (11)	0.003 (8)	0.033 (9)	0.009 (6)
C1X	0.040 (7)	0.045 (8)	0.047 (7)	−0.001 (8)	0.006 (7)	−0.011 (6)
C2X	0.025 (8)	0.054 (10)	0.046 (6)	−0.005 (8)	0.010 (5)	−0.010 (7)
C3X	0.057 (17)	0.083 (11)	0.060 (11)	−0.026 (8)	0.005 (10)	−0.026 (9)
C4X	0.072 (15)	0.081 (12)	0.045 (8)	−0.007 (12)	0.036 (9)	−0.034 (8)
C5X	0.030 (9)	0.076 (14)	0.074 (11)	−0.004 (8)	−0.003 (8)	−0.022 (8)
C6X	0.042 (10)	0.075 (10)	0.048 (8)	0.001 (7)	−0.007 (7)	−0.018 (7)
C7X	0.047 (16)	0.063 (10)	0.047 (11)	0.001 (12)	0.002 (12)	−0.021 (7)
C8X	0.045 (7)	0.054 (7)	0.054 (6)	−0.006 (5)	0.007 (5)	−0.005 (5)
C9X	0.037 (8)	0.068 (11)	0.031 (6)	−0.014 (10)	0.014 (5)	0.004 (5)
C10X	0.042 (9)	0.032 (7)	0.034 (7)	0.011 (5)	0.012 (5)	0.022 (5)
C11X	0.043 (7)	0.035 (6)	0.055 (9)	−0.008 (6)	0.010 (7)	0.009 (4)
C12X	0.046 (7)	0.031 (6)	0.062 (7)	0.000 (7)	0.004 (6)	−0.006 (5)
C13X	0.039 (7)	0.019 (6)	0.060 (7)	0.005 (8)	0.016 (6)	0.005 (6)
C14X	0.082 (18)	0.038 (7)	0.040 (11)	0.002 (8)	0.011 (9)	−0.010 (7)
C15X	0.063 (10)	0.035 (7)	0.080 (15)	−0.005 (8)	0.051 (13)	0.004 (7)
C16X	0.099 (15)	0.023 (8)	0.073 (10)	−0.001 (10)	0.045 (9)	−0.002 (7)
C17X	0.052 (9)	0.046 (7)	0.047 (12)	0.006 (6)	0.018 (10)	−0.005 (7)
C18X	0.031 (6)	0.038 (6)	0.045 (8)	−0.003 (6)	0.011 (6)	0.007 (5)
C19X	0.037 (6)	0.040 (6)	0.048 (7)	0.002 (5)	0.003 (5)	0.000 (5)
C20X	0.0356 (10)	0.0425 (15)	0.0438 (15)	−0.0002 (7)	0.0070 (7)	0.0053 (14)
C21X	0.037 (7)	0.035 (6)	0.041 (9)	−0.003 (5)	0.011 (5)	0.024 (5)
C22X	0.0570 (19)	0.069 (2)	0.0671 (18)	−0.0021 (13)	0.0172 (12)	−0.0084 (12)
C23X	0.039 (8)	0.047 (9)	0.058 (11)	0.004 (8)	0.015 (9)	0.009 (7)

Geometric parameters (Å, º) top

S1—C21	1.686 (4)	S1X—C21X	1.696 (18)
S1—C22	1.801 (3)	S1X—C22X	1.767 (15)
O1—C1	1.350 (5)	O1X—C1X	1.335 (14)
O1—C2	1.374 (2)	O1X—C2X	1.369 (13)
O2—C12	1.367 (3)	O2X—C12X	1.359 (12)
O2—C13	1.376 (3)	O2X—C13X	1.403 (14)
O3—C8	1.337 (2)	O3X—C8X	1.306 (13)
O3—H3B	0.8200	O3X—H3XB	0.8200
O4—C12	1.230 (3)	O4X—C12X	1.243 (14)
O5—C1	1.232 (3)	O5X—C1X	1.256 (14)
O6—C19	1.329 (2)	O6X—C19X	1.337 (13)
O6—H6B	0.8200	O6X—H6XB	0.8200
C1—C9	1.443 (4)	C1X—C9X	1.422 (15)
C2—C7	1.381 (3)	C2X—C7X	1.368 (16)
C2—C3	1.392 (3)	C2X—C3X	1.375 (15)
C3—C4	1.382 (4)	C3X—C4X	1.378 (17)
C3—H3A	0.9300	C3X—H3XA	0.9300
C4—C5	1.385 (4)	C4X—C5X	1.385 (18)
C4—H4A	0.9300	C4X—H4XA	0.9300
C5—C6	1.369 (3)	C5X—C6X	1.348 (15)
C5—H5A	0.9300	C5X—H5XA	0.9300
C6—C7	1.407 (3)	C6X—C7X	1.416 (15)
C6—H6A	0.9300	C6X—H6XA	0.9300
C7—C8	1.439 (3)	C7X—C8X	1.459 (15)
C8—C9	1.365 (2)	C8X—C9X	1.341 (15)
C9—C10	1.519 (4)	C9X—C10X	1.522 (17)
C10—C20	1.521 (3)	C10X—C11X	1.511 (17)
C10—C11	1.524 (3)	C10X—C20X	1.520 (17)
C10—H10A	0.9800	C10X—H10B	0.9800
C11—C19	1.368 (3)	C11X—C19X	1.320 (13)
C11—C12	1.443 (3)	C11X—C12X	1.457 (14)
C13—C18	1.380 (4)	C13X—C18X	1.352 (12)
C13—C14	1.394 (4)	C13X—C14X	1.374 (14)
C14—C15	1.378 (5)	C14X—C15X	1.352 (16)
C14—H14A	0.9300	C14X—H14B	0.9300
C15—C16	1.385 (5)	C15X—C16X	1.367 (15)
C15—H15A	0.9300	C15X—H15B	0.9300
C16—C17	1.372 (4)	C16X—C17X	1.355 (14)
C16—H16A	0.9300	C16X—H16B	0.9300
C17—C18	1.405 (3)	C17X—C18X	1.400 (14)
C17—H17A	0.9300	C17X—H17B	0.9300
C18—C19	1.442 (3)	C18X—C19X	1.496 (13)
C20—C21	1.356 (6)	C20X—C21X	1.36 (2)
C20—C23	1.420 (5)	C20X—C23X	1.42 (2)
C21—H21A	0.9300	C21X—H21B	0.9300
C22—C23	1.358 (5)	C22X—C23X	1.34 (2)
C22—H22A	0.9300	C22X—H22B	0.9300
C23—H23A	0.9300	C23X—H23B	0.9300

C21—S1—C22	92.8 (2)	C21X—S1X—C22X	91.7 (11)
C1—O1—C2	121.19 (19)	C1X—O1X—C2X	118.8 (11)
C12—O2—C13	121.07 (19)	C12X—O2X—C13X	119.8 (9)
C8—O3—H3B	109.5	C8X—O3X—H3XB	109.5
C19—O6—H6B	109.5	C19X—O6X—H6XB	109.5
O5—C1—O1	116.0 (3)	O5X—C1X—O1X	116.0 (13)
O5—C1—C9	124.3 (4)	O5X—C1X—C9X	122.6 (11)
O1—C1—C9	119.6 (3)	O1X—C1X—C9X	121.4 (13)
O1—C2—C7	121.4 (3)	C7X—C2X—O1X	121.7 (15)
O1—C2—C3	116.6 (3)	C7X—C2X—C3X	124.3 (13)
C7—C2—C3	122.0 (2)	O1X—C2X—C3X	113.9 (15)
C4—C3—C2	117.8 (3)	C2X—C3X—C4X	114.9 (16)
C4—C3—H3A	121.1	C2X—C3X—H3XA	122.5
C2—C3—H3A	121.1	C4X—C3X—H3XA	122.5
C3—C4—C5	121.3 (3)	C3X—C4X—C5X	122.0 (18)
C3—C4—H4A	119.4	C3X—C4X—H4XA	119.0
C5—C4—H4A	119.4	C5X—C4X—H4XA	119.0
C6—C5—C4	120.3 (3)	C6X—C5X—C4X	122.1 (18)
C6—C5—H5A	119.8	C6X—C5X—H5XA	119.0
C4—C5—H5A	119.8	C4X—C5X—H5XA	119.0
C5—C6—C7	119.9 (3)	C5X—C6X—C7X	116.9 (16)
C5—C6—H6A	120.1	C5X—C6X—H6XA	121.6
C7—C6—H6A	120.1	C7X—C6X—H6XA	121.6
C2—C7—C6	118.7 (2)	C2X—C7X—C6X	119.2 (14)
C2—C7—C8	117.8 (2)	C2X—C7X—C8X	119.6 (15)
C6—C7—C8	123.5 (2)	C6X—C7X—C8X	120.5 (16)
O3—C8—C9	124.53 (17)	O3X—C8X—C9X	126.1 (13)
O3—C8—C7	114.90 (17)	O3X—C8X—C7X	117.1 (12)
C9—C8—C7	120.56 (18)	C9X—C8X—C7X	116.2 (12)
C8—C9—C1	118.7 (3)	C8X—C9X—C1X	121.5 (14)
C8—C9—C10	122.8 (2)	C8X—C9X—C10X	118.5 (14)
C1—C9—C10	118.5 (3)	C1X—C9X—C10X	118.8 (15)
C9—C10—C20	114.5 (5)	C11X—C10X—C20X	112 (2)
C9—C10—C11	113.0 (3)	C11X—C10X—C9X	115.0 (19)
C20—C10—C11	115.7 (3)	C20X—C10X—C9X	113 (2)
C9—C10—H10A	103.9	C11X—C10X—H10B	105.1
C20—C10—H10A	103.9	C20X—C10X—H10B	105.1
C11—C10—H10A	103.9	C9X—C10X—H10B	105.1
C19—C11—C12	118.5 (2)	C19X—C11X—C12X	121.3 (12)
C19—C11—C10	126.1 (3)	C19X—C11X—C10X	126.5 (14)
C12—C11—C10	115.2 (2)	C12X—C11X—C10X	111.4 (13)
O4—C12—O2	115.5 (2)	O4X—C12X—O2X	117.9 (11)
O4—C12—C11	124.8 (2)	O4X—C12X—C11X	122.5 (11)
O2—C12—C11	119.7 (2)	O2X—C12X—C11X	119.6 (11)
O2—C13—C18	121.1 (3)	C18X—C13X—C14X	123.4 (13)
O2—C13—C14	116.5 (3)	C18X—C13X—O2X	120.6 (12)
C18—C13—C14	122.4 (3)	C14X—C13X—O2X	115.9 (12)
C15—C14—C13	118.0 (3)	C15X—C14X—C13X	117.5 (15)
C15—C14—H14A	121.0	C15X—C14X—H14B	121.3
C13—C14—H14A	121.0	C13X—C14X—H14B	121.3
C14—C15—C16	120.6 (3)	C14X—C15X—C16X	122.7 (15)
C14—C15—H15A	119.7	C14X—C15X—H15B	118.7
C16—C15—H15A	119.7	C16X—C15X—H15B	118.7
C17—C16—C15	121.0 (3)	C17X—C16X—C15X	117.5 (15)
C17—C16—H16A	119.5	C17X—C16X—H16B	121.3
C15—C16—H16A	119.5	C15X—C16X—H16B	121.3
C16—C17—C18	119.7 (3)	C16X—C17X—C18X	122.8 (14)
C16—C17—H17A	120.2	C16X—C17X—H17B	118.6
C18—C17—H17A	120.2	C18X—C17X—H17B	118.6
C13—C18—C17	118.3 (3)	C13X—C18X—C17X	115.9 (12)
C13—C18—C19	118.5 (3)	C13X—C18X—C19X	120.3 (13)
C17—C18—C19	123.2 (3)	C17X—C18X—C19X	123.6 (13)
O6—C19—C11	124.4 (2)	C11X—C19X—O6X	123.0 (14)
O6—C19—C18	115.2 (2)	C11X—C19X—C18X	117.1 (11)
C11—C19—C18	120.5 (2)	O6X—C19X—C18X	119.8 (15)
C21—C20—C23	111.5 (3)	C21X—C20X—C23X	112.2 (15)
C21—C20—C10	125.4 (5)	C21X—C20X—C10X	127 (2)
C23—C20—C10	122.4 (3)	C23X—C20X—C10X	120 (2)
C20—C21—S1	112.8 (3)	C20X—C21X—S1X	110.6 (15)
C20—C21—H21A	123.6	C20X—C21X—H21B	124.7
S1—C21—H21A	123.6	S1X—C21X—H21B	124.7
C23—C22—S1	106.2 (3)	C23X—C22X—S1X	106.7 (17)
C23—C22—H22A	126.9	C23X—C22X—H22B	126.7
S1—C22—H22A	126.9	S1X—C22X—H22B	126.7
C22—C23—C20	116.7 (4)	C22X—C23X—C20X	113 (2)
C22—C23—H23A	121.7	C22X—C23X—H23B	123.4
C20—C23—H23A	121.7	C20X—C23X—H23B	123.4

C2—O1—C1—O5	−174.8 (3)	C2X—O1X—C1X—O5X	177.2 (14)
C2—O1—C1—C9	3.2 (5)	C2X—O1X—C1X—C9X	0 (3)
C1—O1—C2—C7	4.0 (4)	C1X—O1X—C2X—C7X	−4 (4)
C1—O1—C2—C3	−176.7 (3)	C1X—O1X—C2X—C3X	−180.0 (19)
O1—C2—C3—C4	−178.1 (2)	C7X—C2X—C3X—C4X	4 (5)
C7—C2—C3—C4	1.2 (4)	O1X—C2X—C3X—C4X	−180 (2)
C2—C3—C4—C5	−0.7 (5)	C2X—C3X—C4X—C5X	−6 (4)
C3—C4—C5—C6	0.7 (6)	C3X—C4X—C5X—C6X	8 (4)
C4—C5—C6—C7	−1.1 (7)	C4X—C5X—C6X—C7X	−8 (4)
O1—C2—C7—C6	177.6 (3)	O1X—C2X—C7X—C6X	179 (3)
C3—C2—C7—C6	−1.7 (4)	C3X—C2X—C7X—C6X	−5 (6)
O1—C2—C7—C8	−4.9 (4)	O1X—C2X—C7X—C8X	9 (6)
C3—C2—C7—C8	175.8 (2)	C3X—C2X—C7X—C8X	−175 (3)
C5—C6—C7—C2	1.6 (6)	C5X—C6X—C7X—C2X	6 (6)
C5—C6—C7—C8	−175.7 (4)	C5X—C6X—C7X—C8X	176 (3)
C2—C7—C8—O3	179.7 (2)	C2X—C7X—C8X—O3X	177 (3)
C6—C7—C8—O3	−3.0 (4)	C6X—C7X—C8X—O3X	7 (6)
C2—C7—C8—C9	−1.4 (4)	C2X—C7X—C8X—C9X	−11 (6)
C6—C7—C8—C9	175.9 (3)	C6X—C7X—C8X—C9X	179 (4)
O3—C8—C9—C1	−172.9 (3)	O3X—C8X—C9X—C1X	178 (2)
C7—C8—C9—C1	8.2 (4)	C7X—C8X—C9X—C1X	8 (5)
O3—C8—C9—C10	5.5 (4)	O3X—C8X—C9X—C10X	−15 (4)
C7—C8—C9—C10	−173.3 (2)	C7X—C8X—C9X—C10X	175 (3)
O5—C1—C9—C8	168.5 (3)	O5X—C1X—C9X—C8X	−179 (2)
O1—C1—C9—C8	−9.3 (5)	O1X—C1X—C9X—C8X	−2 (4)
O5—C1—C9—C10	−10.0 (6)	O5X—C1X—C9X—C10X	14 (4)
O1—C1—C9—C10	172.2 (3)	O1X—C1X—C9X—C10X	−170 (2)
C8—C9—C10—C20	131.6 (5)	C8X—C9X—C10X—C11X	102 (3)
C1—C9—C10—C20	−50.0 (6)	C1X—C9X—C10X—C11X	−90 (3)
C8—C9—C10—C11	−93.1 (4)	C8X—C9X—C10X—C20X	−127 (5)
C1—C9—C10—C11	85.3 (4)	C1X—C9X—C10X—C20X	41 (6)
C9—C10—C11—C19	−84.8 (5)	C20X—C10X—C11X—C19X	−56 (5)
C20—C10—C11—C19	49.9 (9)	C9X—C10X—C11X—C19X	75 (3)
C9—C10—C11—C12	90.6 (4)	C20X—C10X—C11X—C12X	134 (4)
C20—C10—C11—C12	−134.7 (7)	C9X—C10X—C11X—C12X	−95 (2)
C13—O2—C12—O4	−174.6 (4)	C13X—O2X—C12X—O4X	174.1 (16)
C13—O2—C12—C11	5.4 (5)	C13X—O2X—C12X—C11X	−5 (3)
C19—C11—C12—O4	170.1 (3)	C19X—C11X—C12X—O4X	−166.6 (18)
C10—C11—C12—O4	−5.6 (5)	C10X—C11X—C12X—O4X	4 (3)
C19—C11—C12—O2	−9.9 (6)	C19X—C11X—C12X—O2X	13 (3)
C10—C11—C12—O2	174.3 (3)	C10X—C11X—C12X—O2X	−177.1 (16)
C12—O2—C13—C18	0.8 (9)	C12X—O2X—C13X—C18X	−4 (3)
C12—O2—C13—C14	178.4 (4)	C12X—O2X—C13X—C14X	178 (2)
O2—C13—C14—C15	−177.7 (5)	C18X—C13X—C14X—C15X	2 (4)
C18—C13—C14—C15	−0.2 (9)	O2X—C13X—C14X—C15X	179 (2)
C13—C14—C15—C16	−0.3 (7)	C13X—C14X—C15X—C16X	−4 (4)
C14—C15—C16—C17	0.4 (7)	C14X—C15X—C16X—C17X	4 (4)
C15—C16—C17—C18	0.0 (6)	C15X—C16X—C17X—C18X	−2 (4)
O2—C13—C18—C17	178.1 (5)	C14X—C13X—C18X—C17X	1 (3)
C14—C13—C18—C17	0.6 (9)	O2X—C13X—C18X—C17X	−176.9 (18)
O2—C13—C18—C19	−2.5 (9)	C14X—C13X—C18X—C19X	−176 (2)
C14—C13—C18—C19	180.0 (5)	O2X—C13X—C18X—C19X	6 (3)
C16—C17—C18—C13	−0.5 (7)	C16X—C17X—C18X—C13X	−1 (3)
C16—C17—C18—C19	−179.9 (3)	C16X—C17X—C18X—C19X	175.9 (18)
C12—C11—C19—O6	−173.1 (3)	C12X—C11X—C19X—O6X	168 (2)
C10—C11—C19—O6	2.2 (7)	C10X—C11X—C19X—O6X	−1 (3)
C12—C11—C19—C18	8.2 (6)	C12X—C11X—C19X—C18X	−10 (3)
C10—C11—C19—C18	−176.5 (4)	C10X—C11X—C19X—C18X	−178.7 (17)
C13—C18—C19—O6	179.0 (5)	C13X—C18X—C19X—C11X	1 (3)
C17—C18—C19—O6	−1.6 (5)	C17X—C18X—C19X—C11X	−176 (2)
C13—C18—C19—C11	−2.2 (6)	C13X—C18X—C19X—O6X	−177 (2)
C17—C18—C19—C11	177.2 (4)	C17X—C18X—C19X—O6X	6 (3)
C9—C10—C20—C21	154.2 (10)	C11X—C10X—C20X—C21X	−33 (11)
C11—C10—C20—C21	20.1 (15)	C9X—C10X—C20X—C21X	−165 (8)
C9—C10—C20—C23	−36.7 (13)	C11X—C10X—C20X—C23X	156 (7)
C11—C10—C20—C23	−170.8 (9)	C9X—C10X—C20X—C23X	24 (10)
C23—C20—C21—S1	0.5 (13)	C23X—C20X—C21X—S1X	−3 (9)
C10—C20—C21—S1	170.7 (9)	C10X—C20X—C21X—S1X	−174 (7)
C22—S1—C21—C20	−1.0 (9)	C22X—S1X—C21X—C20X	14 (5)
C21—S1—C22—C23	1.3 (4)	C21X—S1X—C22X—C23X	−21 (3)
S1—C22—C23—C20	−1.3 (8)	S1X—C22X—C23X—C20X	24 (7)
C21—C20—C23—C22	0.6 (13)	C21X—C20X—C23X—C22X	−15 (10)
C10—C20—C23—C22	−169.9 (8)	C10X—C20X—C23X—C22X	157 (6)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3B···O4	0.82	1.89	2.7049 (19)	180
O6—H6B···O5	0.82	1.79	2.612 (2)	179
C21—H21A···O4ⁱ	0.93	2.56	3.475 (8)	168
O3X—H3XB···O4X	0.82	1.86	2.682 (15)	178
O6X—H6XB···O5X	0.82	1.69	2.49 (2)	168
C23X—H23B···O3Xⁱ	0.93	2.53	3.31 (5)	142

Symmetry code: (i) −x+2, y−1/2, −z+3/2.

Experimental details

Crystal data
Chemical formula	C₂₃H₁₄O₆S
M_r	418.40
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	297
a, b, c (Å)	7.8225 (2), 8.9426 (2), 27.1317 (6)
β (°)	100.679 (1)
V (Å³)	1865.09 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.22
Crystal size (mm)	0.49 × 0.44 × 0.16

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.902, 0.966
No. of measured, independent and observed [I > 2σ(I)] reflections	20839, 5420, 3497
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.106, 1.02
No. of reflections	5420
No. of parameters	524
No. of restraints	252
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.21

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
O3—H3B···O4	0.82	1.89	2.7049 (19)	180
O6—H6B···O5	0.82	1.79	2.612 (2)	179
C21—H21A···O4ⁱ	0.93	2.56	3.475 (8)	168
O3X—H3XB···O4X	0.82	1.86	2.682 (15)	178
O6X—H6XB···O5X	0.82	1.69	2.49 (2)	168
C23X—H23B···O3Xⁱ	0.93	2.53	3.31 (5)	142

Symmetry code: (i) −x+2, y−1/2, −z+3/2.

Footnotes

‡Additional correspondence author, e-mail: oocw@usm.my.

§Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

The authors are thankful to Universiti Sains Malaysia (USM) for providing the necessary research facilities and RU research funding under the grant No. 1001/PKIMIA/811134. MA also thanks Universiti Sains Malaysia for the award of post-doctoral fellowship. HKF and MMR thank USM for the Research University Grant (No. 1001/PFIZIK/811160).

References

Abdelhafez, O. M., Amin, K. M., Batran, R. Z., Maher, T. J., Nada, S. A. & Sethumadhavan, S. (2010). Bioorg. Med. Chem. 18, 3371–3378. Web of Science CrossRef CAS PubMed Google Scholar
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Huang, W. Y., Cai, Y. Z. & Zhang, Y. (2010). Nutr. Cancer 62, 1–20. Web of Science CrossRef PubMed Google Scholar
Jacquot, Y., Bermont, L., Giorgi, H., Refouvelet, B., Adessi, G., Daubrosse, E. & Xicluna, A. (2001). Eur. J. Med. Chem. 36, 127–136. Web of Science CrossRef PubMed CAS Google Scholar
Kokil, G. R., Rewatkar, P. V., Gosain, S., Aggarwal, S., Verma, A., Kalra, A. & Thareja, S. (2010). Lett. Drug Des. Discov. 7, 46–49. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siddiqui, Z. N. & Asad, M. (2010). Indian J. Chem. Soc. 87, 501–506. CAS Google Scholar
Skulnick, H. I., Johnson, P. D., Aristoff, P. A., Morris, J. K. & Lovasz, K. D. (1997). J. Med. Chem. 40, 1149–1164. CrossRef CAS PubMed Web of Science Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sullivan, W. R., Hubbner, C. F., Stahmann, M. A. & Link, K. P. (1943). J. Am. Chem. Soc. 65, 2288–2291. CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.