(SP)-Menthyl benzyl­(phenyl)­phospho­nate

Wang, W.-M.; Zhao, C.-Q.

doi:10.1107/S1600536810009372

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 66| Part 4| April 2010| Page o863

doi:10.1107/S1600536810009372

Open

access

(S_P)-Menthyl benzyl(phenyl)phosphonate

Wei-Min Wang ^a and Chang-Qiu Zhao ^a ^*

^aCollege of Chemistry and Chemical Engineering, Liaocheng University, Shandong 252059, People's Republic of China
^*Correspondence e-mail: literabc@hotmail.com

(Received 9 March 2010; accepted 12 March 2010; online 17 March 2010)

The title compound, C₂₃H₃₁O₂P, has three fully extended substituents around the P-atom chiral centre, forming an S_P configuration. The phenyl rings are inclined at a dihedral angle of 3.2 (3)°.

Related literature

For general background to phosphorus-sulfur compounds, see: Dilworth & Wheatley (2000 ); Chae et al. (1994 ). For alkylates of phosphorus-sulfur compounds, see: Aitken (2005 ).

Experimental

Crystal data

C₂₃H₃₁O₂P
M_r = 370.45
Monoclinic, P 2₁
a = 12.4777 (11) Å
b = 5.7970 (7) Å
c = 15.4190 (19) Å
β = 100.727 (1)°
V = 1095.8 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.14 mm⁻¹
T = 298 K
0.43 × 0.11 × 0.10 mm

Data collection

Siemens SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.943, T_max = 0.986
5541 measured reflections
3576 independent reflections
2596 reflections with I > 2σ(I)
R_int = 0.085

Refinement

R[F² > 2σ(F²)] = 0.066
wR(F²) = 0.170
S = 0.89
3576 reflections
238 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.23 e Å⁻³
Absolute structure: Flack (1983 ), 1432 Friedel pairs
Flack parameter: −0.17 (16)

Data collection: SMART (Siemens, 1996 ); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810009372/bx2269sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810009372/bx2269Isup2.hkl

checkCIF report

Comment top

Phosphorus-sulfur compounds, especially P-chiral, have extensive applications (Dilworth et al. 2000; Chae et al. 1994), wherein their alkylates are of significant senes, for example, they usually act as common ligands (Aitken et al. 2005). The title compound is a P-chiral compounds, which can be synthesized by (R_p)-O-menthyl S-ethyl phenylphosphonothioate and benzylmagnesium chloride. The compound is comprised of fully extended substituents: phenyl, menthyloxy and benzyl, and O atom which form a irregular tetrahedron, (Table 1). The phenyl rings makes a dihedral angle of 3.2 (3)°.The six-membered menthyloxy ring is in a chair conformation. The molecular structure is stabilized by a intramolecular C—H··· O hydrogen bond [C···O =2.893 (5) Å , C—H··· O =104°]. There are no further significant intermolecular interactions.

Related literature top

For general background to phosphorus-sulfur compounds, see: Dilworth et al.(2000); Chae et al. (1994). For the alkylates of phosphorus-sulfur compounds, see: Aitken et al. (2005).

Experimental top

(R_p)-O-menthyl S-ethyl phenylphosphonothioate (0.3 mmol) was added to a stirred ether solution of benzylmagnesium chloride (0.6 mmol) in a Schlenk tube under nitrogen and the mixture was stirred for 24 h at room temperature. After washing with water, the resulting solution was purified by silica gel plate to afford optically pure product. The crystal suitable for X-ray diffraction was obtained from recrystallization with ethyl ether/hexane.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. The molecular structure of the compound. H atoms have been omitted for clarity.

(S_P)-Menthyl benzyl(phenyl)phosphonate top

Crystal data top

C₂₃H₃₁O₂P	F(000) = 400
M_r = 370.45	D_x = 1.123 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 1629 reflections
a = 12.4777 (11) Å	θ = 2.7–25.0°
b = 5.7970 (7) Å	µ = 0.14 mm⁻¹
c = 15.4190 (19) Å	T = 298 K
β = 100.727 (1)°	Block, colorless
V = 1095.8 (2) Å³	0.43 × 0.11 × 0.10 mm
Z = 2

Data collection top

Siemens SMART CCD area-detector diffractometer	3576 independent reflections
Radiation source: fine-focus sealed tube	2596 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.085
phi and ω scans	θ_max = 25.0°, θ_min = 1.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −14→14
T_min = 0.943, T_max = 0.986	k = −6→6
5541 measured reflections	l = −15→18

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.066	H-atom parameters constrained
wR(F²) = 0.170	w = 1/[σ²(F_o²) + (0.1052P)²] where P = (F_o² + 2F_c²)/3
S = 0.89	(Δ/σ)_max < 0.001
3576 reflections	Δρ_max = 0.28 e Å⁻³
238 parameters	Δρ_min = −0.23 e Å⁻³
1 restraint	Absolute structure: Flack (1983), 1432 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.17 (16)

Crystal data top

C₂₃H₃₁O₂P	V = 1095.8 (2) Å³
M_r = 370.45	Z = 2
Monoclinic, P2₁	Mo Kα radiation
a = 12.4777 (11) Å	µ = 0.14 mm⁻¹
b = 5.7970 (7) Å	T = 298 K
c = 15.4190 (19) Å	0.43 × 0.11 × 0.10 mm
β = 100.727 (1)°

Data collection top

Siemens SMART CCD area-detector diffractometer	3576 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	2596 reflections with I > 2σ(I)
T_min = 0.943, T_max = 0.986	R_int = 0.085
5541 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.066	H-atom parameters constrained
wR(F²) = 0.170	Δρ_max = 0.28 e Å⁻³
S = 0.89	Δρ_min = −0.23 e Å⁻³
3576 reflections	Absolute structure: Flack (1983), 1432 Friedel pairs
238 parameters	Absolute structure parameter: −0.17 (16)
1 restraint

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
P1	0.14134 (8)	0.32764 (18)	0.12780 (6)	0.0440 (3)
O1	0.2011 (2)	0.2676 (5)	0.22583 (18)	0.0495 (7)
O2	0.1092 (2)	0.5709 (5)	0.11455 (18)	0.0539 (8)
C1	0.2811 (3)	0.3635 (8)	0.3776 (3)	0.0513 (11)
H1	0.3316	0.2327	0.3810	0.062*
C2	0.2606 (3)	0.4484 (9)	0.2817 (3)	0.0494 (10)
H2	0.2140	0.5856	0.2776	0.059*
C3	0.3653 (4)	0.5136 (9)	0.2527 (3)	0.0604 (13)
H3A	0.3492	0.5651	0.1918	0.072*
H3B	0.4119	0.3788	0.2556	0.072*
C4	0.4259 (4)	0.7041 (10)	0.3099 (3)	0.0736 (15)
H4	0.3776	0.8387	0.3045	0.088*
C5	0.4456 (4)	0.6286 (13)	0.4061 (3)	0.0831 (17)
H5A	0.4964	0.5004	0.4142	0.100*
H5B	0.4786	0.7548	0.4430	0.100*
C6	0.3419 (4)	0.5571 (10)	0.4352 (3)	0.0694 (14)
H6A	0.2942	0.6901	0.4329	0.083*
H6B	0.3590	0.5049	0.4959	0.083*
C7	0.1778 (4)	0.2749 (10)	0.4090 (3)	0.0665 (14)
H7	0.1455	0.1554	0.3672	0.080*
C8	0.0910 (5)	0.4614 (15)	0.4086 (4)	0.104 (2)
H8A	0.0268	0.3938	0.4239	0.157*
H8B	0.0731	0.5286	0.3508	0.157*
H8C	0.1187	0.5787	0.4508	0.157*
C9	0.2060 (5)	0.1607 (12)	0.4997 (3)	0.0865 (18)
H9A	0.2317	0.2756	0.5435	0.130*
H9B	0.2620	0.0472	0.4992	0.130*
H9C	0.1422	0.0876	0.5134	0.130*
C10	0.5316 (5)	0.7791 (15)	0.2790 (4)	0.113 (3)
H10A	0.5812	0.6511	0.2838	0.170*
H10B	0.5649	0.9037	0.3153	0.170*
H10C	0.5143	0.8289	0.2186	0.170*
C11	0.2347 (3)	0.2350 (7)	0.0575 (3)	0.0445 (10)
C12	0.2528 (4)	0.3793 (9)	−0.0106 (3)	0.0615 (14)
H12	0.2167	0.5200	−0.0204	0.074*
C13	0.3260 (4)	0.3096 (13)	−0.0641 (3)	0.0790 (15)
H13	0.3387	0.4050	−0.1097	0.095*
C14	0.3790 (4)	0.1029 (11)	−0.0502 (4)	0.0762 (15)
H14	0.4277	0.0581	−0.0859	0.091*
C15	0.3601 (4)	−0.0387 (11)	0.0170 (4)	0.0776 (15)
H15	0.3964	−0.1791	0.0267	0.093*
C16	0.2876 (4)	0.0258 (9)	0.0701 (3)	0.0652 (13)
H16	0.2744	−0.0724	0.1146	0.078*
C17	0.0306 (3)	0.1248 (8)	0.1089 (3)	0.0511 (10)
H17A	−0.0110	0.1479	0.0498	0.061*
H17B	0.0603	−0.0303	0.1117	0.061*
C18	−0.0457 (3)	0.1452 (8)	0.1747 (3)	0.0490 (10)
C19	−0.1144 (4)	0.3305 (10)	0.1742 (3)	0.0668 (12)
H19	−0.1153	0.4478	0.1329	0.080*
C20	−0.1828 (4)	0.3417 (13)	0.2360 (4)	0.0828 (16)
H20	−0.2284	0.4684	0.2363	0.099*
C21	−0.1837 (5)	0.1675 (13)	0.2966 (4)	0.0861 (18)
H21	−0.2302	0.1752	0.3371	0.103*
C22	−0.1159 (5)	−0.0153 (12)	0.2966 (4)	0.0910 (19)
H22	−0.1155	−0.1324	0.3379	0.109*
C23	−0.0479 (4)	−0.0298 (10)	0.2365 (3)	0.0689 (13)
H23	−0.0028	−0.1576	0.2369	0.083*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
P1	0.0524 (5)	0.0365 (6)	0.0430 (5)	0.0020 (6)	0.0084 (4)	−0.0002 (5)
O1	0.0601 (16)	0.0395 (19)	0.0464 (15)	0.0000 (13)	0.0034 (12)	−0.0034 (12)
O2	0.0638 (16)	0.0401 (18)	0.0577 (18)	0.0061 (15)	0.0106 (14)	−0.0018 (13)
C1	0.054 (2)	0.055 (3)	0.044 (2)	0.005 (2)	0.0090 (17)	−0.002 (2)
C2	0.052 (2)	0.048 (3)	0.047 (2)	0.003 (2)	0.0061 (19)	−0.008 (2)
C3	0.067 (3)	0.068 (4)	0.047 (2)	−0.007 (2)	0.012 (2)	0.000 (2)
C4	0.069 (3)	0.087 (4)	0.064 (3)	−0.018 (3)	0.009 (2)	−0.013 (3)
C5	0.074 (3)	0.114 (5)	0.058 (3)	−0.023 (3)	0.004 (2)	−0.015 (3)
C6	0.066 (3)	0.090 (4)	0.052 (3)	−0.009 (3)	0.011 (2)	−0.014 (3)
C7	0.078 (3)	0.078 (4)	0.047 (2)	−0.008 (3)	0.022 (2)	−0.005 (2)
C8	0.075 (3)	0.136 (6)	0.107 (5)	0.023 (4)	0.031 (3)	0.026 (4)
C9	0.111 (4)	0.089 (5)	0.067 (4)	−0.004 (4)	0.036 (3)	0.001 (3)
C10	0.101 (4)	0.152 (8)	0.089 (4)	−0.061 (5)	0.022 (3)	−0.019 (5)
C11	0.047 (2)	0.042 (3)	0.044 (2)	−0.0032 (18)	0.0047 (17)	0.0013 (17)
C12	0.067 (3)	0.062 (4)	0.058 (3)	0.002 (2)	0.017 (2)	0.006 (2)
C13	0.088 (3)	0.091 (4)	0.066 (3)	−0.005 (4)	0.034 (3)	0.006 (4)
C14	0.070 (3)	0.080 (4)	0.087 (4)	−0.008 (3)	0.037 (3)	−0.020 (3)
C15	0.075 (3)	0.058 (3)	0.107 (4)	0.010 (3)	0.032 (3)	−0.007 (3)
C16	0.070 (3)	0.056 (3)	0.075 (3)	0.008 (3)	0.029 (3)	0.008 (2)
C17	0.057 (2)	0.046 (3)	0.049 (2)	0.004 (2)	0.0082 (19)	−0.0035 (19)
C18	0.055 (2)	0.043 (3)	0.048 (2)	−0.005 (2)	0.0085 (18)	−0.0033 (19)
C19	0.070 (3)	0.056 (3)	0.076 (3)	0.010 (3)	0.017 (2)	0.009 (3)
C20	0.069 (3)	0.084 (4)	0.100 (4)	0.003 (3)	0.028 (3)	−0.013 (4)
C21	0.078 (4)	0.103 (5)	0.088 (4)	−0.013 (4)	0.041 (3)	−0.007 (4)
C22	0.112 (5)	0.088 (5)	0.082 (4)	−0.012 (4)	0.042 (3)	0.018 (4)
C23	0.085 (3)	0.053 (3)	0.072 (3)	−0.002 (3)	0.025 (3)	0.013 (3)

Geometric parameters (Å, º) top

P1—O2	1.470 (3)	C9—H9C	0.9600
P1—O1	1.595 (3)	C10—H10A	0.9600
P1—C17	1.796 (4)	C10—H10B	0.9600
P1—C11	1.814 (4)	C10—H10C	0.9600
O1—C2	1.467 (5)	C11—C16	1.377 (6)
C1—C2	1.533 (5)	C11—C12	1.394 (6)
C1—C6	1.540 (6)	C12—C13	1.400 (7)
C1—C7	1.548 (6)	C12—H12	0.9300
C1—H1	0.9800	C13—C14	1.366 (8)
C2—C3	1.507 (6)	C13—H13	0.9300
C2—H2	0.9800	C14—C15	1.377 (8)
C3—C4	1.524 (7)	C14—H14	0.9300
C3—H3A	0.9700	C15—C16	1.380 (7)
C3—H3B	0.9700	C15—H15	0.9300
C4—C5	1.522 (7)	C16—H16	0.9300
C4—C10	1.546 (7)	C17—C18	1.519 (6)
C4—H4	0.9800	C17—H17A	0.9700
C5—C6	1.504 (7)	C17—H17B	0.9700
C5—H5A	0.9700	C18—C19	1.374 (6)
C5—H5B	0.9700	C18—C23	1.396 (6)
C6—H6A	0.9700	C19—C20	1.395 (7)
C6—H6B	0.9700	C19—H19	0.9300
C7—C8	1.529 (8)	C20—C21	1.377 (9)
C7—C9	1.528 (7)	C20—H20	0.9300
C7—H7	0.9800	C21—C22	1.356 (9)
C8—H8A	0.9600	C21—H21	0.9300
C8—H8B	0.9600	C22—C23	1.370 (7)
C8—H8C	0.9600	C22—H22	0.9300
C9—H9A	0.9600	C23—H23	0.9300
C9—H9B	0.9600

O2—P1—O1	114.13 (15)	C7—C9—H9A	109.5
O2—P1—C17	115.1 (2)	C7—C9—H9B	109.5
O1—P1—C17	102.76 (18)	H9A—C9—H9B	109.5
O2—P1—C11	112.96 (18)	C7—C9—H9C	109.5
O1—P1—C11	105.23 (17)	H9A—C9—H9C	109.5
C17—P1—C11	105.6 (2)	H9B—C9—H9C	109.5
C2—O1—P1	119.8 (3)	C4—C10—H10A	109.5
C2—C1—C6	107.3 (4)	C4—C10—H10B	109.5
C2—C1—C7	114.1 (3)	H10A—C10—H10B	109.5
C6—C1—C7	114.2 (4)	C4—C10—H10C	109.5
C2—C1—H1	106.9	H10A—C10—H10C	109.5
C6—C1—H1	106.9	H10B—C10—H10C	109.5
C7—C1—H1	106.9	C16—C11—C12	119.6 (4)
O1—C2—C3	112.1 (3)	C16—C11—P1	121.4 (3)
O1—C2—C1	108.2 (4)	C12—C11—P1	119.0 (3)
C3—C2—C1	111.6 (3)	C11—C12—C13	119.1 (5)
O1—C2—H2	108.3	C11—C12—H12	120.5
C3—C2—H2	108.3	C13—C12—H12	120.5
C1—C2—H2	108.3	C14—C13—C12	120.7 (5)
C2—C3—C4	111.9 (4)	C14—C13—H13	119.7
C2—C3—H3A	109.2	C12—C13—H13	119.7
C4—C3—H3A	109.2	C13—C14—C15	119.7 (5)
C2—C3—H3B	109.2	C13—C14—H14	120.2
C4—C3—H3B	109.2	C15—C14—H14	120.2
H3A—C3—H3B	107.9	C14—C15—C16	120.5 (6)
C5—C4—C3	109.2 (5)	C14—C15—H15	119.7
C5—C4—C10	112.9 (4)	C16—C15—H15	119.7
C3—C4—C10	112.6 (5)	C11—C16—C15	120.4 (5)
C5—C4—H4	107.3	C11—C16—H16	119.8
C3—C4—H4	107.3	C15—C16—H16	119.8
C10—C4—H4	107.3	C18—C17—P1	113.5 (3)
C6—C5—C4	112.2 (4)	C18—C17—H17A	108.9
C6—C5—H5A	109.2	P1—C17—H17A	108.9
C4—C5—H5A	109.2	C18—C17—H17B	108.9
C6—C5—H5B	109.2	P1—C17—H17B	108.9
C4—C5—H5B	109.2	H17A—C17—H17B	107.7
H5A—C5—H5B	107.9	C19—C18—C23	118.7 (4)
C5—C6—C1	112.8 (4)	C19—C18—C17	121.7 (4)
C5—C6—H6A	109.0	C23—C18—C17	119.6 (4)
C1—C6—H6A	109.0	C18—C19—C20	119.6 (5)
C5—C6—H6B	109.0	C18—C19—H19	120.2
C1—C6—H6B	109.0	C20—C19—H19	120.2
H6A—C6—H6B	107.8	C21—C20—C19	120.9 (6)
C8—C7—C9	110.6 (4)	C21—C20—H20	119.6
C8—C7—C1	113.2 (5)	C19—C20—H20	119.6
C9—C7—C1	111.5 (4)	C22—C21—C20	119.3 (5)
C8—C7—H7	107.0	C22—C21—H21	120.4
C9—C7—H7	107.0	C20—C21—H21	120.4
C1—C7—H7	107.0	C21—C22—C23	120.8 (5)
C7—C8—H8A	109.5	C21—C22—H22	119.6
C7—C8—H8B	109.5	C23—C22—H22	119.6
H8A—C8—H8B	109.5	C22—C23—C18	120.7 (5)
C7—C8—H8C	109.5	C22—C23—H23	119.6
H8A—C8—H8C	109.5	C18—C23—H23	119.6
H8B—C8—H8C	109.5

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···O1	0.98	2.49	2.893 (5)	104

Experimental details

Crystal data
Chemical formula	C₂₃H₃₁O₂P
M_r	370.45
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	298
a, b, c (Å)	12.4777 (11), 5.7970 (7), 15.4190 (19)
β (°)	100.727 (1)
V (Å³)	1095.8 (2)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.14
Crystal size (mm)	0.43 × 0.11 × 0.10

Data collection
Diffractometer	Siemens SMART CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.943, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections	5541, 3576, 2596
R_int	0.085
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.066, 0.170, 0.89
No. of reflections	3576
No. of parameters	238
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.23
Absolute structure	Flack (1983), 1432 Friedel pairs
Absolute structure parameter	−0.17 (16)

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

P1—O2	1.470 (3)	P1—C17	1.796 (4)
P1—O1	1.595 (3)	P1—C11	1.814 (4)

O2—P1—O1	114.13 (15)	O2—P1—C11	112.96 (18)
O2—P1—C17	115.1 (2)	O1—P1—C11	105.23 (17)
O1—P1—C17	102.76 (18)	C17—P1—C11	105.6 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7···O1	0.98	2.49	2.893 (5)	104

Acknowledgements

We acknowledge the financial support of the Natural Science Foundation of China (No. 20772055).

References

Aitken, R. A. (2005). Comprehensive Organic Functional Group Transformations II, pp. 539–573. Amsterdam:Elsevier CrossRef Google Scholar
Chae, M. Y., Postula, J. F. & Raushel, F. M. (1994). Bioorg. Med. Chem. Lett. 4, 1473–1478. CrossRef CAS Web of Science Google Scholar
Dilworth, J. R. & Wheatley, N. (2000). Coord. Chem. Rev. 199, 89–158. Web of Science CrossRef CAS Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Siemens (1996). SMART and SAINT. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Google Scholar