3-Benzyl-6-methyl-2-sulfanylidene-2,3-di­hydroquinazolin-4(1H)-one

Al-Salahi, R.; Al-Omar, M.; El-Subbagh, H.; Hemamalini, M.; Fun, H.-K.

doi:10.1107/S1600536812006009

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 68| Part 3| March 2012| Pages o717-o718

doi:10.1107/S1600536812006009

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3-Benzyl-6-methyl-2-sulfanylidene-2,3-dihydroquinazolin-4(1H)-one

Rashad Al-Salahi,^a Mohamed Al-Omar,^b Hussein El-Subbagh,^c Madhukar Hemamalini ^d and Hoong-Kun Fun ^d ^*‡

^aDepartment of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia, ^bDrug Exploration and Development Chair, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia, ^cCollege of Pharmaceutical Sciences, Future University, Cairo 12311, Egypt, and ^dX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 6 February 2012; accepted 10 February 2012; online 17 February 2012)

In the title compound, C₁₆H₁₄N₂OS, the quinazoline ring system is essentially planar, with a maximum deviation of 0.029 (3) Å. The dihedral angle between the quinazoline and benzene rings is 88.4 (2)°. In the crystal, adjacent molecules are connected via pairs of N—H⋯S and C—H⋯O hydrogen bonds, which generate R²₂(8) and R²₂(10) graph-set motifs, respectively, resulting in a supramolecular chain along the a axis.

Related literature

For details and applications of quinazoline compounds, see: Roth & Fenner (2000 ); Jantova et al. (2004 ); Harris & Thorarensen (2004 ); Andries et al. (2005 ); Al-Rashood et al. (2006 ); Ghorab et al. (2007 ); Rádl et al. (2000 ); Klepser & Klepser (1997 ); Al-Omar et al. (2004 ); Al-Omary et al. (2010 ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ). For bond-length data, see: Allen et al. (1987 ).

Experimental

Crystal data

C₁₆H₁₄N₂OS
M_r = 282.35
Monoclinic, C 2/c
a = 24.2438 (18) Å
b = 5.1618 (5) Å
c = 24.4265 (17) Å
β = 111.532 (6)°
V = 2843.4 (4) Å³
Z = 8
Cu Kα radiation
μ = 1.99 mm⁻¹
T = 296 K
0.83 × 0.12 × 0.06 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.289, T_max = 0.890
9528 measured reflections
2592 independent reflections
1421 reflections with I > 2σ(I)
R_int = 0.104

Refinement

R[F² > 2σ(F²)] = 0.055
wR(F²) = 0.166
S = 0.93
2592 reflections
182 parameters
H-atom parameters constrained
Δρ_max = 0.24 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
N1—H1A⋯S1ⁱ	0.86	2.50	3.335 (3)	165
C4—H4A⋯O1ⁱⁱ	0.93	2.41	3.295 (4)	159
Symmetry codes: (i) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]$ ; (ii) -x, -y+2, -z.

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/S1600536812006009/is5070sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812006009/is5070Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536812006009/is5070Isup3.cml

checkCIF report

Comment top

Quinazoline moiety is present in many classes of biologically-active compounds. A number of them have been clinically used as antifungal, antibacterial and antiprotozoic drugs (Roth & Fenner, 2000; Jantova et al., 2004; Harris & Thorarensen, 2004), as well as antituberculotic agents (Andries et al., 2005). Furthermore, they have drawn much attention due to their broad range of pharmacological properties which include antitumor (Al-Rashood et al., 2006), anticancer (Ghorab et al., 2007) and analgesic (Rádl et al., 2000) properties. Certain quinazoline analogs also showed remarkable activity against the opportunistic infections of Pneumocystis carinii and Toxoplasma gondii. Those microorganisms proved to be the priniciple cause of death in patients with immunocompromised diseases such as acquired immune deficiency syndrome (Klepser & Klepser, 1997). This work is a continuation of this program with the aim of obtaining an interesting series of quinazolines that contain the thioxo functional group which was identified as a possible pharmacophore of the antimicrobial activity (Al-Omar et al., 2004; Al-Omary et al., 2010).

The molecular structure of the title compound is shown in Fig. 1. The quinazoline (N1,N2/C1–C8) ring is essentially planar, with a maximum deviation of 0.029 (3) Å for atom C2. The dihedral angle between the quinazoline (N1,N2/C1–C8) and the benzene (C10–C15) rings is 88.4 (2)°. The bond lengths (Allen et al., 1987) and angles are within normal ranges. In the crystal, (Fig. 2), the adjacent molecules are connected via a pair of N—H···S and C—H···O (Table 1) hydrogen bonds, generating R²₂(8) and R²₂(10) graph-set motifs (Bernstein et al., 1995), respectively, resulting in a supramolecular [100] chain.

Related literature top

For details and applications of quinazoline compounds, see: Roth & Fenner (2000); Jantova et al. (2004); Harris & Thorarensen (2004); Andries et al. (2005); Al-Rashood et al. (2006); Ghorab et al. (2007); Rádl et al. (2000); Klepser & Klepser (1997); Al-Omar et al. (2004); Al-Omary et al. (2010). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987).

Experimental top

A mixture of benzyl isothiocyanate (10 mmol) and 2-amino-5-methyl benzoic acid (10 mmol) in ethanol (30 ml) was heated under reflux in the presence of triethylamine (5 mmol) for 2 h. After cooling, the mixture was poured into ice/water. The resulting solid was filtered, washed with water and dried. Recrystallization from ethanol gave 3-benzyl-2,3-dihydro-6-methyl-2-thioxo-quinazoline-4(1H)-one as colorless crystals.

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 30% probability displacement ellipsoids.
	Fig. 2. The crystal packing view of the title compound along the b axis.

3-Benzyl-6-methyl-2-sulfanylidene-2,3-dihydroquinazolin-4(1H)-one top

Crystal data top

C₁₆H₁₄N₂OS	F(000) = 1184
M_r = 282.35	D_x = 1.319 Mg m⁻³
Monoclinic, C2/c	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -C 2yc	Cell parameters from 339 reflections
a = 24.2438 (18) Å	θ = 3.9–53.5°
b = 5.1618 (5) Å	µ = 1.99 mm⁻¹
c = 24.4265 (17) Å	T = 296 K
β = 111.532 (6)°	Needle, colourless
V = 2843.4 (4) Å³	0.83 × 0.12 × 0.06 mm
Z = 8

Data collection top

Bruker SMART APEXII CCD diffractometer	2592 independent reflections
Radiation source: fine-focus sealed tube	1421 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.104
ϕ and ω scans	θ_max = 69.8°, θ_min = 3.9°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −29→29
T_min = 0.289, T_max = 0.890	k = −6→5
9528 measured reflections	l = −28→28

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)] = 0.055	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.166	H-atom parameters constrained
S = 0.93	w = 1/[σ²(F_o²) + (0.0875P)²] where P = (F_o² + 2F_c²)/3
2592 reflections	(Δ/σ)_max = 0.001
182 parameters	Δρ_max = 0.24 e Å⁻³
0 restraints	Δρ_min = −0.21 e Å⁻³

Crystal data top

C₁₆H₁₄N₂OS	V = 2843.4 (4) Å³
M_r = 282.35	Z = 8
Monoclinic, C2/c	Cu Kα radiation
a = 24.2438 (18) Å	µ = 1.99 mm⁻¹
b = 5.1618 (5) Å	T = 296 K
c = 24.4265 (17) Å	0.83 × 0.12 × 0.06 mm
β = 111.532 (6)°

Data collection top

Bruker SMART APEXII CCD diffractometer	2592 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	1421 reflections with I > 2σ(I)
T_min = 0.289, T_max = 0.890	R_int = 0.104
9528 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.055	0 restraints
wR(F²) = 0.166	H-atom parameters constrained
S = 0.93	Δρ_max = 0.24 e Å⁻³
2592 reflections	Δρ_min = −0.21 e Å⁻³
182 parameters

Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
S1	0.22029 (4)	0.1447 (2)	0.07055 (4)	0.0718 (3)
N1	0.17921 (10)	0.4985 (6)	−0.01167 (11)	0.0630 (7)
H1A	0.2097	0.4590	−0.0199	0.076*
N2	0.12318 (10)	0.4401 (5)	0.04598 (11)	0.0574 (7)
O1	0.04534 (10)	0.7057 (5)	0.03541 (11)	0.0747 (7)
C1	0.17206 (13)	0.3706 (7)	0.03308 (14)	0.0594 (8)
C2	0.08423 (13)	0.6424 (7)	0.01808 (14)	0.0600 (8)
C3	0.09395 (12)	0.7664 (7)	−0.03127 (13)	0.0585 (8)
C4	0.05611 (13)	0.9575 (7)	−0.06444 (14)	0.0630 (9)
H4A	0.0243	1.0100	−0.0544	0.076*
C5	0.06438 (15)	1.0717 (7)	−0.11196 (15)	0.0691 (9)
C6	0.11382 (16)	0.9891 (8)	−0.12434 (16)	0.0763 (10)
H6A	0.1206	1.0638	−0.1559	0.092*
C7	0.15210 (15)	0.8048 (7)	−0.09221 (15)	0.0715 (10)
H7A	0.1848	0.7578	−0.1013	0.086*
C8	0.14201 (13)	0.6879 (7)	−0.04573 (14)	0.0578 (8)
C9	0.10920 (14)	0.2997 (7)	0.09172 (15)	0.0657 (9)
H9A	0.1263	0.1276	0.0958	0.079*
H9B	0.0665	0.2799	0.0788	0.079*
C10	0.13111 (14)	0.4281 (7)	0.15093 (14)	0.0641 (9)
C11	0.1103 (2)	0.3376 (10)	0.1930 (2)	0.0988 (15)
H11A	0.0831	0.2022	0.1840	0.119*
C12	0.1298 (3)	0.4483 (15)	0.2483 (2)	0.131 (2)
H12A	0.1144	0.3902	0.2758	0.157*
C13	0.1710 (3)	0.6401 (16)	0.2634 (2)	0.133 (2)
H13A	0.1854	0.7057	0.3015	0.160*
C14	0.1912 (2)	0.7364 (11)	0.2216 (2)	0.1082 (15)
H14A	0.2179	0.8737	0.2306	0.130*
C15	0.17129 (17)	0.6268 (8)	0.16567 (16)	0.0783 (11)
H15A	0.1856	0.6898	0.1377	0.094*
C16	0.02217 (18)	1.2711 (9)	−0.14931 (18)	0.0893 (12)
H16B	−0.0064	1.3143	−0.1321	0.134*
H16A	0.0021	1.2027	−0.1881	0.134*
H16C	0.0438	1.4238	−0.1516	0.134*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.0640 (5)	0.0875 (7)	0.0707 (6)	0.0172 (4)	0.0327 (5)	0.0084 (5)
N1	0.0558 (14)	0.083 (2)	0.0576 (17)	0.0153 (13)	0.0295 (14)	0.0029 (15)
N2	0.0510 (13)	0.0688 (18)	0.0577 (16)	0.0036 (11)	0.0264 (13)	−0.0049 (13)
O1	0.0601 (12)	0.0924 (19)	0.0855 (17)	0.0135 (11)	0.0430 (13)	−0.0007 (13)
C1	0.0500 (16)	0.076 (2)	0.0554 (19)	0.0024 (14)	0.0231 (16)	−0.0121 (17)
C2	0.0498 (16)	0.073 (2)	0.059 (2)	0.0022 (14)	0.0228 (16)	−0.0124 (17)
C3	0.0472 (16)	0.076 (2)	0.051 (2)	−0.0010 (14)	0.0169 (16)	−0.0104 (17)
C4	0.0543 (17)	0.070 (2)	0.066 (2)	0.0069 (15)	0.0225 (17)	−0.0068 (18)
C5	0.065 (2)	0.074 (2)	0.066 (2)	0.0057 (16)	0.0211 (18)	−0.0006 (19)
C6	0.077 (2)	0.086 (3)	0.072 (2)	0.0089 (18)	0.035 (2)	0.008 (2)
C7	0.068 (2)	0.090 (3)	0.068 (2)	0.0134 (17)	0.0375 (19)	0.009 (2)
C8	0.0472 (16)	0.073 (2)	0.0540 (19)	0.0062 (13)	0.0194 (15)	−0.0060 (16)
C9	0.0629 (19)	0.065 (2)	0.080 (2)	−0.0013 (14)	0.0393 (19)	−0.0001 (18)
C10	0.0643 (18)	0.074 (2)	0.063 (2)	0.0196 (16)	0.0343 (18)	0.0090 (18)
C11	0.115 (3)	0.114 (4)	0.090 (3)	0.020 (3)	0.065 (3)	0.028 (3)
C12	0.150 (6)	0.185 (7)	0.080 (4)	0.064 (5)	0.069 (4)	0.043 (4)
C13	0.131 (5)	0.196 (7)	0.068 (3)	0.061 (4)	0.031 (4)	−0.018 (4)
C14	0.108 (4)	0.117 (4)	0.092 (3)	0.010 (3)	0.027 (3)	−0.030 (3)
C15	0.082 (2)	0.089 (3)	0.066 (3)	0.002 (2)	0.029 (2)	−0.011 (2)
C16	0.082 (3)	0.091 (3)	0.092 (3)	0.014 (2)	0.028 (2)	0.012 (2)

Geometric parameters (Å, º) top

S1—C1	1.667 (3)	C7—H7A	0.9300
N1—C1	1.342 (4)	C9—C10	1.500 (5)
N1—C8	1.382 (4)	C9—H9A	0.9700
N1—H1A	0.8600	C9—H9B	0.9700
N2—C1	1.381 (3)	C10—C15	1.369 (5)
N2—C2	1.405 (4)	C10—C11	1.381 (5)
N2—C9	1.472 (4)	C11—C12	1.382 (7)
O1—C2	1.212 (3)	C11—H11A	0.9300
C2—C3	1.458 (4)	C12—C13	1.357 (9)
C3—C4	1.388 (5)	C12—H12A	0.9300
C3—C8	1.396 (4)	C13—C14	1.377 (8)
C4—C5	1.381 (5)	C13—H13A	0.9300
C4—H4A	0.9300	C14—C15	1.390 (6)
C5—C6	1.406 (5)	C14—H14A	0.9300
C5—C16	1.501 (5)	C15—H15A	0.9300
C6—C7	1.359 (5)	C16—H16B	0.9600
C6—H6A	0.9300	C16—H16A	0.9600
C7—C8	1.385 (4)	C16—H16C	0.9600

C1—N1—C8	126.0 (2)	N2—C9—C10	114.6 (3)
C1—N1—H1A	117.0	N2—C9—H9A	108.6
C8—N1—H1A	117.0	C10—C9—H9A	108.6
C1—N2—C2	124.2 (3)	N2—C9—H9B	108.6
C1—N2—C9	120.1 (3)	C10—C9—H9B	108.6
C2—N2—C9	115.7 (2)	H9A—C9—H9B	107.6
N1—C1—N2	115.9 (3)	C15—C10—C11	118.5 (4)
N1—C1—S1	121.1 (2)	C15—C10—C9	123.4 (3)
N2—C1—S1	123.0 (2)	C11—C10—C9	118.1 (4)
O1—C2—N2	120.1 (3)	C10—C11—C12	120.0 (5)
O1—C2—C3	123.6 (3)	C10—C11—H11A	120.0
N2—C2—C3	116.3 (2)	C12—C11—H11A	120.0
C4—C3—C8	119.5 (3)	C13—C12—C11	121.3 (5)
C4—C3—C2	121.5 (3)	C13—C12—H12A	119.3
C8—C3—C2	119.0 (3)	C11—C12—H12A	119.3
C5—C4—C3	121.7 (3)	C12—C13—C14	119.3 (5)
C5—C4—H4A	119.1	C12—C13—H13A	120.4
C3—C4—H4A	119.1	C14—C13—H13A	120.4
C4—C5—C6	116.7 (3)	C13—C14—C15	119.5 (6)
C4—C5—C16	121.8 (3)	C13—C14—H14A	120.3
C6—C5—C16	121.5 (3)	C15—C14—H14A	120.3
C7—C6—C5	122.9 (3)	C10—C15—C14	121.3 (4)
C7—C6—H6A	118.5	C10—C15—H15A	119.3
C5—C6—H6A	118.5	C14—C15—H15A	119.3
C6—C7—C8	119.3 (3)	C5—C16—H16B	109.5
C6—C7—H7A	120.3	C5—C16—H16A	109.5
C8—C7—H7A	120.3	H16B—C16—H16A	109.5
N1—C8—C7	122.0 (3)	C5—C16—H16C	109.5
N1—C8—C3	118.3 (3)	H16B—C16—H16C	109.5
C7—C8—C3	119.7 (3)	H16A—C16—H16C	109.5

C8—N1—C1—N2	−0.9 (5)	C1—N1—C8—C7	−178.2 (3)
C8—N1—C1—S1	179.7 (3)	C1—N1—C8—C3	3.6 (5)
C2—N2—C1—N1	−4.2 (5)	C6—C7—C8—N1	179.7 (4)
C9—N2—C1—N1	176.0 (3)	C6—C7—C8—C3	−2.1 (6)
C2—N2—C1—S1	175.1 (2)	C4—C3—C8—N1	179.5 (3)
C9—N2—C1—S1	−4.6 (4)	C2—C3—C8—N1	−1.3 (5)
C1—N2—C2—O1	−173.6 (3)	C4—C3—C8—C7	1.3 (5)
C9—N2—C2—O1	6.1 (5)	C2—C3—C8—C7	−179.6 (3)
C1—N2—C2—C3	6.2 (5)	C1—N2—C9—C10	97.0 (3)
C9—N2—C2—C3	−174.1 (3)	C2—N2—C9—C10	−82.7 (3)
O1—C2—C3—C4	−4.2 (5)	N2—C9—C10—C15	−13.4 (5)
N2—C2—C3—C4	176.0 (3)	N2—C9—C10—C11	167.7 (3)
O1—C2—C3—C8	176.6 (3)	C15—C10—C11—C12	0.3 (6)
N2—C2—C3—C8	−3.1 (5)	C9—C10—C11—C12	179.3 (4)
C8—C3—C4—C5	0.5 (5)	C10—C11—C12—C13	−2.3 (8)
C2—C3—C4—C5	−178.6 (3)	C11—C12—C13—C14	3.8 (10)
C3—C4—C5—C6	−1.4 (5)	C12—C13—C14—C15	−3.2 (8)
C3—C4—C5—C16	177.6 (3)	C11—C10—C15—C14	0.2 (6)
C4—C5—C6—C7	0.5 (6)	C9—C10—C15—C14	−178.7 (4)
C16—C5—C6—C7	−178.5 (4)	C13—C14—C15—C10	1.3 (7)
C5—C6—C7—C8	1.3 (6)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···S1ⁱ	0.86	2.50	3.335 (3)	165
C4—H4A···O1ⁱⁱ	0.93	2.41	3.295 (4)	159

Symmetry codes: (i) −x+1/2, −y+1/2, −z; (ii) −x, −y+2, −z.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₄N₂OS
M_r	282.35
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	24.2438 (18), 5.1618 (5), 24.4265 (17)
β (°)	111.532 (6)
V (Å³)	2843.4 (4)
Z	8
Radiation type	Cu Kα
µ (mm⁻¹)	1.99
Crystal size (mm)	0.83 × 0.12 × 0.06

Data collection
Diffractometer	Bruker SMART APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.289, 0.890
No. of measured, independent and observed [I > 2σ(I)] reflections	9528, 2592, 1421
R_int	0.104
(sin θ/λ)_max (Å⁻¹)	0.609

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.055, 0.166, 0.93
No. of reflections	2592
No. of parameters	182
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.24, −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
N1—H1A···S1ⁱ	0.86	2.50	3.335 (3)	165
C4—H4A···O1ⁱⁱ	0.93	2.41	3.295 (4)	159

Symmetry codes: (i) −x+1/2, −y+1/2, −z; (ii) −x, −y+2, −z.

Footnotes

‡Alternative address: College of Pharmacy (Visiting Professor), King Saud University, PO Box 2457, Riyadh 11451, Saudi Arabia. Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

RAS, MAO and HES express their gratitude to Mr Hazem Ghabbour, X-ray Division of the Pharmaceutical Chemistry Department, King Saud University, for valuable help in the determination of the X-ray crystal structure. MH and HFK thank the Malaysian Government and Universiti Sains Malaysia for Research University Grant No. 1001/PFIZIK/811160. MH also thanks Universiti Sains Malaysia for a postdoctoral research fellowship.

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