Isopropyl 2-(5-fluoro-3-methyl­sulfinyl-1-benzofuran-2-yl)acetate

Choi, H.D.; Seo, P.J.; Son, B.W.; Lee, U.

doi:10.1107/S1600536809037003

organic compounds

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ISSN: 2056-9890

Volume 65| Part 10| October 2009| Page o2488

doi:10.1107/S1600536809037003

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Isopropyl 2-(5-fluoro-3-methylsulfinyl-1-benzofuran-2-yl)acetate

Hong Dae Choi,^a Pil Ja Seo,^a Byeng Wha Son ^b and Uk Lee ^b ^*

^aDepartment of Chemistry, Dongeui University, San 24 Kaya-dong Busanjin-gu, Busan 614-714, Republic of Korea, and ^bDepartment of Chemistry, Pukyong National University, 599-1 Daeyeon 3-dong, Nam-gu, Busan 608-737, Republic of Korea
^*Correspondence e-mail: uklee@pknu.ac.kr

(Received 9 September 2009; accepted 13 September 2009; online 19 September 2009)

In the title compound, C₁₄H₁₅FO₄S, the O atom and the methyl group of the methylsulfinyl substituent are located on opposite sides of the plane of the benzofuran fragment which is essentially planar with a mean deviation of 0.008 (1) Å from its least-squares plane. The crystal structure stabilized by three different intermolecular non-classical C—H⋯O hydrogen bonds. The crystal structure also exhibits aromatic π–π interactions between the benzene rings of adjacent benzofuran ring systems [centroid–centroid distance = 3.688 (2) Å]

Related literature

For the crystal structures of similar alkyl 2-(5-fluoro-3-methylsulfinyl-1-benzofuran-2-yl) acetate derivatives, see: Choi et al. (2009a ,b ). For the pharmacological activity of benzofuran compounds, see: Howlett et al. (1999 ); Twyman & Allsop (1999 ).

Experimental

Crystal data

C₁₄H₁₅FO₄S
M_r = 298.32
Monoclinic, P 2₁ /c
a = 11.6332 (6) Å
b = 14.9522 (7) Å
c = 8.2333 (4) Å
β = 102.277 (1)°
V = 1399.36 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.25 mm⁻¹
T = 173 K
0.25 × 0.20 × 0.16 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2000 ) T_min = 0.940, T_max = 0.961
12229 measured reflections
3173 independent reflections
2476 reflections with I > 2σ(I)
R_int = 0.043

Refinement

R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.098
S = 1.09
3173 reflections
182 parameters
H-atom parameters constrained
Δρ_max = 0.39 e Å⁻³
Δρ_min = −0.39 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O3ⁱ	0.93	2.50	3.370 (2)	155
C6—H6⋯O2ⁱⁱ	0.93	2.54	3.369 (2)	149
C9—H9B⋯O4ⁱⁱⁱ	0.97	2.26	3.228 (2)	176
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) -x+1, -y+1, -z+2; (iii) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997 ) and DIAMOND (Brandenburg, 1998 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablock I. DOI: 10.1107/S1600536809037003/bq2158sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809037003/bq2158Isup2.hkl

checkCIF report

Comment top

Molecules involving benzofuran skeleton have attracted particular interest in view of their biological and pharmacological properties (Howlett et al., 1999; Twyman & Allsop, 1999). As a part of our ongoing studies of the effect of side chain substituents on the solid state structures of alkyl 2-(5-fluoro-3-methylsulfinyl-1-benzofuran-2-yl) acetate analogues (Choi et al., 2009a,b), we report the crystal structure of the title compound (Fig. 1).

The benzofuran unit is essentially planar, with a mean deviation of 0.008 (1) Å from the least-squares plane defined by the nine constituent atoms. The crystal packing (Fig. 2) is stabilized by three intermolecular non-classical C—H···O hydrogen bonds; the first between an H atom of the benzofuran ring and the oxygen of the C═O unit, with a C5–H5···O3ⁱ, the second between an H atom of the benzofuran ring and the oxygen of the isopropoxy group, with a C6—H6···O2ⁱⁱ, the third between a methylene H atom and the oxygen of the S═O unit, with a C9—H9B···O4ⁱⁱⁱ, respectively (Table 1). The crystal packing (Fig. 2) is further stabilized by aromatic π···π interactions between the benzene rings of neighboring molecules, with a Cg···Cgⁱ distance of 3.688 (2) Å (Cg is the centroid of the C2–C7 benzene ring).

Related literature top

For the crystal structures of similar alkyl 2-(5-fluoro-3-methylsulfinyl-1-benzofuran-2-yl) acetate derivatives, see: Choi et al. (2009a,b). For the pharmacological activity of benzofuran compounds, see: Howlett et al. (1999); Twyman & Allsop (1999).

Experimental top

77% 3-chloroperoxybenzoic acid (247 mg, 1.1 mmol) was added in small portions to a stirred solution of isopropyl 2-(5-fluoro-3-methylsulfanyl-1-benzofuran-2-yl) acetate (282 mg, 1.0 mmol) in dichloromethane (30 ml) at 273 K. After being stirred for 4 h at room temperature, the mixture was washed with saturated sodium bicarbonate solution and the organic layer was separated, dried over magnesium sulfate, filtered and concentrated in vacuum. The residue was purified by column chromatography (hexane–ethyl acetate, 1:2 v/v) to afford the title compound as a colorless solid [yield 83%, m.p. 391–392 K; R_f = 0.67 (hexane–ethyl acetate, 1;2 v/v )]. Single crystals suitable for X-ray diffraction were prepared by evaporation of a solution of the title compound in acetone at room temperature. Spectroscopic analysis: EI-MS 298 [M⁺].

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97 (Bruker, 2001).

Figures top

	Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The C—H···O and π···π interactions (dotted lines) in the title compound. Cg denotes the benzene ring centroid. [Symmetry codes: (i) - x + 1, - y + 1, - z + 1; (ii) - x + 1, - y + 1, - z + 2; (iii) x, - y, z + 1/2; (iv) x, - y + 1/2, z - 1/2.]

Isopropyl 2-(5-fluoro-3-methylsulfinyl-1-benzofuran-2-yl)acetate top

Crystal data top

C₁₄H₁₅FO₄S	F(000) = 624
M_r = 298.32	D_x = 1.416 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5216 reflections
a = 11.6332 (6) Å	θ = 2.3–27.4°
b = 14.9522 (7) Å	µ = 0.25 mm⁻¹
c = 8.2333 (4) Å	T = 173 K
β = 102.277 (1)°	Block, colorless
V = 1399.36 (12) Å³	0.25 × 0.20 × 0.16 mm
Z = 4

Data collection top

Bruker SMART CCD diffractometer	3173 independent reflections
Radiation source: fine-focus sealed tube	2476 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.043
Detector resolution: 10.0 pixels mm^-1	θ_max = 27.5°, θ_min = 1.8°
ϕ and ω scans	h = −14→15
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	k = −19→19
T_min = 0.940, T_max = 0.961	l = −10→10
12229 measured reflections

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.098	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0423P)² + 0.5417P] where P = (F_o² + 2F_c²)/3
3173 reflections	(Δ/σ)_max = 0.001
182 parameters	Δρ_max = 0.39 e Å⁻³
0 restraints	Δρ_min = −0.39 e Å⁻³

Crystal data top

C₁₄H₁₅FO₄S	V = 1399.36 (12) Å³
M_r = 298.32	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.6332 (6) Å	µ = 0.25 mm⁻¹
b = 14.9522 (7) Å	T = 173 K
c = 8.2333 (4) Å	0.25 × 0.20 × 0.16 mm
β = 102.277 (1)°

Data collection top

Bruker SMART CCD diffractometer	3173 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	2476 reflections with I > 2σ(I)
T_min = 0.940, T_max = 0.961	R_int = 0.043
12229 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.036	0 restraints
wR(F²) = 0.098	H-atom parameters constrained
S = 1.09	Δρ_max = 0.39 e Å⁻³
3173 reflections	Δρ_min = −0.39 e Å⁻³
182 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
S	0.16889 (4)	0.32823 (3)	0.59899 (5)	0.02546 (13)
F	0.53377 (11)	0.32123 (8)	0.19202 (14)	0.0427 (3)
O1	0.47612 (10)	0.43326 (8)	0.79555 (14)	0.0242 (3)
O2	0.19830 (10)	0.54133 (8)	1.03615 (14)	0.0264 (3)
O3	0.17889 (11)	0.53806 (9)	0.75830 (15)	0.0329 (3)
O4	0.17181 (12)	0.23235 (9)	0.54858 (18)	0.0393 (3)
C1	0.31410 (14)	0.36896 (11)	0.6411 (2)	0.0222 (3)
C2	0.40529 (14)	0.36553 (11)	0.5455 (2)	0.0222 (3)
C3	0.41420 (16)	0.33514 (12)	0.3875 (2)	0.0264 (4)
H3	0.3516	0.3078	0.3155	0.032*
C4	0.52168 (16)	0.34834 (12)	0.3458 (2)	0.0289 (4)
C5	0.61801 (16)	0.38849 (12)	0.4473 (2)	0.0284 (4)
H5	0.6880	0.3950	0.4111	0.034*
C6	0.60937 (14)	0.41885 (12)	0.6032 (2)	0.0257 (4)
H6	0.6722	0.4464	0.6744	0.031*
C7	0.50247 (14)	0.40604 (11)	0.6470 (2)	0.0224 (3)
C8	0.36106 (14)	0.40933 (11)	0.7872 (2)	0.0229 (4)
C9	0.31082 (15)	0.43478 (12)	0.9330 (2)	0.0252 (4)
H9A	0.3743	0.4524	1.0239	0.030*
H9B	0.2725	0.3831	0.9689	0.030*
C10	0.22306 (14)	0.51050 (12)	0.8949 (2)	0.0234 (4)
C11	0.11677 (16)	0.61749 (12)	1.0234 (2)	0.0298 (4)
H11	0.0555	0.6121	0.9218	0.036*
C12	0.06204 (17)	0.61224 (13)	1.1728 (2)	0.0340 (4)
H12A	0.0191	0.5572	1.1699	0.051*
H12B	0.0094	0.6618	1.1718	0.051*
H12C	0.1226	0.6143	1.2721	0.051*
C13	0.1857 (2)	0.70278 (14)	1.0176 (3)	0.0504 (6)
H13A	0.2183	0.7028	0.9199	0.076*
H13B	0.2482	0.7064	1.1146	0.076*
H13C	0.1344	0.7533	1.0147	0.076*
C14	0.11297 (18)	0.39058 (15)	0.4135 (2)	0.0397 (5)
H14A	0.1529	0.3725	0.3282	0.060*
H14B	0.1258	0.4532	0.4356	0.060*
H14C	0.0302	0.3794	0.3773	0.060*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S	0.0205 (2)	0.0281 (2)	0.0274 (2)	−0.00173 (17)	0.00402 (16)	−0.00285 (18)
F	0.0481 (7)	0.0526 (8)	0.0320 (6)	−0.0002 (6)	0.0189 (5)	−0.0125 (5)
O1	0.0211 (6)	0.0286 (6)	0.0221 (6)	−0.0011 (5)	0.0031 (5)	−0.0028 (5)
O2	0.0283 (6)	0.0295 (7)	0.0213 (6)	0.0066 (5)	0.0046 (5)	−0.0010 (5)
O3	0.0323 (7)	0.0439 (8)	0.0226 (6)	0.0096 (6)	0.0062 (5)	0.0042 (6)
O4	0.0339 (7)	0.0291 (7)	0.0529 (9)	−0.0065 (6)	0.0048 (6)	−0.0116 (6)
C1	0.0203 (8)	0.0202 (8)	0.0253 (8)	0.0012 (6)	0.0030 (6)	0.0000 (7)
C2	0.0222 (8)	0.0196 (8)	0.0241 (8)	0.0022 (6)	0.0033 (6)	0.0002 (7)
C3	0.0281 (9)	0.0243 (9)	0.0258 (8)	0.0002 (7)	0.0037 (7)	−0.0046 (7)
C4	0.0359 (10)	0.0275 (9)	0.0254 (9)	0.0052 (8)	0.0113 (8)	−0.0022 (7)
C5	0.0256 (9)	0.0279 (9)	0.0339 (9)	0.0044 (7)	0.0108 (7)	0.0028 (8)
C6	0.0200 (8)	0.0263 (9)	0.0298 (9)	0.0015 (7)	0.0029 (7)	0.0005 (7)
C7	0.0241 (8)	0.0213 (8)	0.0217 (8)	0.0028 (7)	0.0042 (6)	0.0000 (6)
C8	0.0198 (8)	0.0233 (8)	0.0251 (8)	0.0009 (6)	0.0037 (6)	0.0026 (7)
C9	0.0263 (9)	0.0283 (9)	0.0205 (8)	0.0009 (7)	0.0037 (7)	0.0005 (7)
C10	0.0215 (8)	0.0274 (9)	0.0214 (8)	−0.0046 (7)	0.0052 (6)	−0.0015 (7)
C11	0.0299 (9)	0.0320 (10)	0.0269 (9)	0.0098 (8)	0.0049 (7)	0.0021 (8)
C12	0.0301 (9)	0.0382 (11)	0.0359 (10)	0.0079 (8)	0.0119 (8)	0.0019 (9)
C13	0.0648 (15)	0.0322 (11)	0.0636 (15)	0.0043 (10)	0.0345 (13)	0.0087 (11)
C14	0.0302 (10)	0.0517 (13)	0.0329 (10)	0.0040 (9)	−0.0030 (8)	0.0067 (9)

Geometric parameters (Å, º) top

S—O4	1.4949 (14)	C6—C7	1.380 (2)
S—C1	1.7595 (17)	C6—H6	0.9300
S—C14	1.7894 (19)	C8—C9	1.491 (2)
F—C4	1.365 (2)	C9—C10	1.512 (2)
O1—C8	1.3731 (19)	C9—H9A	0.9700
O1—C7	1.384 (2)	C9—H9B	0.9700
O2—C10	1.338 (2)	C11—C12	1.502 (2)
O2—C11	1.472 (2)	C11—C13	1.513 (3)
O3—C10	1.205 (2)	C11—H11	0.9800
C1—C8	1.353 (2)	C12—H12A	0.9600
C1—C2	1.450 (2)	C12—H12B	0.9600
C2—C7	1.394 (2)	C12—H12C	0.9600
C2—C3	1.402 (2)	C13—H13A	0.9600
C3—C4	1.380 (2)	C13—H13B	0.9600
C3—H3	0.9300	C13—H13C	0.9600
C4—C5	1.384 (3)	C14—H14A	0.9600
C5—C6	1.385 (3)	C14—H14B	0.9600
C5—H5	0.9300	C14—H14C	0.9600

O4—S—C1	108.00 (8)	C10—C9—H9A	109.0
O4—S—C14	106.75 (10)	C8—C9—H9B	109.0
C1—S—C14	98.47 (9)	C10—C9—H9B	109.0
C8—O1—C7	106.03 (12)	H9A—C9—H9B	107.8
C10—O2—C11	117.35 (13)	O3—C10—O2	124.43 (16)
C8—C1—C2	107.15 (14)	O3—C10—C9	125.76 (15)
C8—C1—S	121.23 (13)	O2—C10—C9	109.79 (14)
C2—C1—S	131.57 (13)	O2—C11—C12	106.27 (14)
C7—C2—C3	119.14 (15)	O2—C11—C13	108.45 (16)
C7—C2—C1	104.64 (14)	C12—C11—C13	112.95 (17)
C3—C2—C1	136.21 (16)	O2—C11—H11	109.7
C4—C3—C2	115.75 (16)	C12—C11—H11	109.7
C4—C3—H3	122.1	C13—C11—H11	109.7
C2—C3—H3	122.1	C11—C12—H12A	109.5
F—C4—C3	117.80 (16)	C11—C12—H12B	109.5
F—C4—C5	117.32 (16)	H12A—C12—H12B	109.5
C3—C4—C5	124.87 (16)	C11—C12—H12C	109.5
C4—C5—C6	119.52 (16)	H12A—C12—H12C	109.5
C4—C5—H5	120.2	H12B—C12—H12C	109.5
C6—C5—H5	120.2	C11—C13—H13A	109.5
C7—C6—C5	116.35 (16)	C11—C13—H13B	109.5
C7—C6—H6	121.8	H13A—C13—H13B	109.5
C5—C6—H6	121.8	C11—C13—H13C	109.5
C6—C7—O1	124.87 (15)	H13A—C13—H13C	109.5
C6—C7—C2	124.37 (16)	H13B—C13—H13C	109.5
O1—C7—C2	110.75 (14)	S—C14—H14A	109.5
C1—C8—O1	111.43 (14)	S—C14—H14B	109.5
C1—C8—C9	132.54 (16)	H14A—C14—H14B	109.5
O1—C8—C9	115.98 (14)	S—C14—H14C	109.5
C8—C9—C10	112.79 (14)	H14A—C14—H14C	109.5
C8—C9—H9A	109.0	H14B—C14—H14C	109.5

O4—S—C1—C8	−126.67 (15)	C3—C2—C7—C6	0.0 (3)
C14—S—C1—C8	122.54 (15)	C1—C2—C7—C6	−178.66 (16)
O4—S—C1—C2	50.55 (18)	C3—C2—C7—O1	178.64 (14)
C14—S—C1—C2	−60.23 (18)	C1—C2—C7—O1	0.01 (18)
C8—C1—C2—C7	−0.17 (18)	C2—C1—C8—O1	0.27 (19)
S—C1—C2—C7	−177.69 (14)	S—C1—C8—O1	178.10 (11)
C8—C1—C2—C3	−178.44 (19)	C2—C1—C8—C9	177.57 (17)
S—C1—C2—C3	4.0 (3)	S—C1—C8—C9	−4.6 (3)
C7—C2—C3—C4	0.1 (2)	C7—O1—C8—C1	−0.26 (18)
C1—C2—C3—C4	178.20 (18)	C7—O1—C8—C9	−178.05 (14)
C2—C3—C4—F	−178.87 (15)	C1—C8—C9—C10	−69.4 (2)
C2—C3—C4—C5	0.0 (3)	O1—C8—C9—C10	107.82 (16)
F—C4—C5—C6	178.67 (16)	C11—O2—C10—O3	−3.7 (2)
C3—C4—C5—C6	−0.2 (3)	C11—O2—C10—C9	178.11 (14)
C4—C5—C6—C7	0.3 (3)	C8—C9—C10—O3	13.5 (2)
C5—C6—C7—O1	−178.66 (15)	C8—C9—C10—O2	−168.35 (14)
C5—C6—C7—C2	−0.2 (3)	C10—O2—C11—C12	154.84 (15)
C8—O1—C7—C6	178.81 (16)	C10—O2—C11—C13	−83.45 (19)
C8—O1—C7—C2	0.15 (18)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O3ⁱ	0.93	2.50	3.370 (2)	155
C6—H6···O2ⁱⁱ	0.93	2.54	3.369 (2)	149
C9—H9B···O4ⁱⁱⁱ	0.97	2.26	3.228 (2)	176

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

Experimental details

Crystal data
Chemical formula	C₁₄H₁₅FO₄S
M_r	298.32
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	173
a, b, c (Å)	11.6332 (6), 14.9522 (7), 8.2333 (4)
β (°)	102.277 (1)
V (Å³)	1399.36 (12)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.25
Crystal size (mm)	0.25 × 0.20 × 0.16

Data collection
Diffractometer	Bruker SMART CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2000)
T_min, T_max	0.940, 0.961
No. of measured, independent and observed [I > 2σ(I)] reflections	12229, 3173, 2476
R_int	0.043
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.098, 1.09
No. of reflections	3173
No. of parameters	182
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.39, −0.39

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 1998), SHELXL97 (Bruker, 2001).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O3ⁱ	0.93	2.50	3.370 (2)	155.3
C6—H6···O2ⁱⁱ	0.93	2.54	3.369 (2)	148.6
C9—H9B···O4ⁱⁱⁱ	0.97	2.26	3.228 (2)	176.2

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

References

Brandenburg, K. (1998). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
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Volume 65| Part 10| October 2009| Page o2488

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