Cinnamyl 8-meth­oxy-2-oxo-2H-chromene-3-carboxyl­ate

Xu, C.-L.; Liu, S.-Y.; Wang, C.-X.; Zhao, M.-Q.

doi:10.1107/S1600536809041725

organic compounds

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ISSN: 2056-9890

Volume 65| Part 11| November 2009| Page o2817

https://doi.org/10.1107/S1600536809041725

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Cinnamyl 8-methoxy-2-oxo-2H-chromene-3-carboxylate

Cui-Lian Xu,^a ^* Shan-Yu Liu,^b Cai-Xia Wang ^a and Ming-Qin Zhao ^b

^aCollege of Sciences, Henan Agricultural University, Zhengzhou 450002, People's Republic of China, and ^bCollege of Tobacco Science, Henan Agricultural University, Zhengzhou 450002, People's Republic of China
^*Correspondence e-mail: xucuilian666@126.com

(Received 16 September 2009; accepted 12 October 2009; online 23 October 2009)

In the crystal structure of the title compound, C₂₀H₁₆O₅, the molecule assumes an E configuration with the benzene ring and chromenecarboxyl group located on opposite ends of the C=C double bond. The chromene ring system and benzene ring are oriented at a dihedral angle of 74.66 (12)°. Weak intermolecular C—H⋯O hydrogen bonding is present in the crystal structure.

Related literature

For applications of coumarins and related compounds, see: Hoult & Paya (1996 ); Yu et al. (2003 , 2007 ); Finn et al. (2004 ).

Experimental

Crystal data

C₂₀H₁₆O₅
M_r = 336.33
Monoclinic, P 2₁ /c
a = 19.226 (4) Å
b = 9.5483 (19) Å
c = 9.0046 (18) Å
β = 90.97 (3)°
V = 1652.8 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 296 K
0.20 × 0.17 × 0.17 mm

Data collection

Bruker SMART CCD area detector diffractometer
Absorption correction: none
4903 measured reflections
2834 independent reflections
2157 reflections with I > 2σ(I)
R_int = 0.053

Refinement

R[F² > 2σ(F²)] = 0.065
wR(F²) = 0.155
S = 1.15
2834 reflections
228 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4A⋯O3ⁱ	0.93	2.51	3.429 (3)	170
C17—H17A⋯O4ⁱⁱ	0.93	2.44	3.294 (4)	153
Symmetry codes: (i) x, y+1, z; (ii) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: SMART (Bruker, 2007 ); cell refinement: SAINT (Bruker, 2007); 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.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536809041725/xu2613sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536809041725/xu2613Isup2.hkl

checkCIF report

Comment top

Coumarins and related compounds, kinds of plant-derived compounds, have diverse biological activities, including anti-HIV, anti-bacterial, anti-inflammatory, anti-proliferative and antioxidant properties (Hoult & Paya, 1996; Yu et al., 2003; Finn et al., 2004; Yu et al., 2007). It thus appeared of interest to synthesize the compounds with coumarin-skeleton. As part of work, we have synthesized the title compound (I) and report its crystal structure here.

The title molecule crystallizes in the E conformation, with an C12-C13-C14-C15 torsion angle of -179.5 (3)°. The 8-methoxy-2H-chromen-2-one ring and the C15-benzene ring make a dihedral of 74.66 (12)°.

In the crystal structure, an intramolecular C—H···O hydrogen bond is observed and helps to stablize the conformation of the molecule.

Related literature top

For applications of coumarins and related compounds, see: Hoult & Paya (1996); Yu et al. (2003, 2007); Finn et al. (2004).

Experimental top

A solution of cinnamic alcohol (7.2 mmol) dissolved in dried methyl dichloride (DCM) (25 ml) was added dropwise to a solution of 2-oxo-2H-chromene-3-acyl chloride (7.2 mmol) dissolved in DCM (25 ml) and triethylamine (1 ml) at room temperature. The reaction mixture was stirred for 24 h, monitored by TLC. The reaction mixture was neutralized with 5% HCl and washed by saturated NaHCO₃ solution and brine, respectively. The organic phase is dried over Na₂SO₄ and evaporated under the reduced pressure. The resulting residue was purified by column chromatography (EtOAc:petroleum ether) to give the purified compound.

Structure description top

In the crystal structure, an intramolecular C—H···O hydrogen bond is observed and helps to stablize the conformation of the molecule.

For applications of coumarins and related compounds, see: Hoult & Paya (1996); Yu et al. (2003, 2007); Finn et al. (2004).

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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).

Figures top

Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level for non-H atoms.

cinnamyl 8-methoxy-2-oxo-2H-chromene-3-carboxylate top

Crystal data top

C₂₀H₁₆O₅	F(000) = 704
M_r = 336.33	D_x = 1.352 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2834 reflections
a = 19.226 (4) Å	θ = 3.1–24.2°
b = 9.5483 (19) Å	µ = 0.10 mm⁻¹
c = 9.0046 (18) Å	T = 296 K
β = 90.97 (3)°	Block, colorless
V = 1652.8 (6) Å³	0.20 × 0.17 × 0.17 mm
Z = 4

Data collection top

Bruker SMART CCD area detector diffractometer	2157 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.053
Graphite monochromator	θ_max = 25.0°, θ_min = 1.1°
ω scans	h = −22→22
4903 measured reflections	k = −11→11
2834 independent reflections	l = 0→10

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)] = 0.065	H-atom parameters constrained
wR(F²) = 0.155	w = 1/[σ²(F_o²) + (0.0659P)² + 0.2012P] where P = (F_o² + 2F_c²)/3
S = 1.15	(Δ/σ)_max = 0.001
2834 reflections	Δρ_max = 0.24 e Å⁻³
228 parameters	Δρ_min = −0.20 e Å⁻³
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.024 (3)

Crystal data top

C₂₀H₁₆O₅	V = 1652.8 (6) Å³
M_r = 336.33	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 19.226 (4) Å	µ = 0.10 mm⁻¹
b = 9.5483 (19) Å	T = 296 K
c = 9.0046 (18) Å	0.20 × 0.17 × 0.17 mm
β = 90.97 (3)°

Data collection top

Bruker SMART CCD area detector diffractometer	2157 reflections with I > 2σ(I)
4903 measured reflections	R_int = 0.053
2834 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.065	0 restraints
wR(F²) = 0.155	H-atom parameters constrained
S = 1.15	Δρ_max = 0.24 e Å⁻³
2834 reflections	Δρ_min = −0.20 e Å⁻³
228 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 > σ(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	0.04001 (9)	0.88854 (18)	0.70962 (19)	0.0610 (5)
O2	0.11713 (7)	0.72996 (15)	0.54027 (17)	0.0463 (4)
O3	0.15130 (10)	0.51497 (17)	0.4995 (2)	0.0705 (6)
O4	0.25790 (11)	0.4732 (2)	0.3000 (3)	0.0885 (7)
O5	0.28952 (8)	0.66346 (19)	0.17300 (19)	0.0617 (5)
C1	0.12199 (11)	0.8722 (2)	0.5210 (2)	0.0414 (6)
C2	0.08113 (11)	0.9568 (3)	0.6115 (3)	0.0497 (6)
C3	0.08597 (14)	1.0996 (3)	0.5946 (3)	0.0652 (8)
H3A	0.0593	1.1578	0.6536	0.078*
C4	0.13001 (15)	1.1585 (3)	0.4910 (3)	0.0710 (8)
H4A	0.1323	1.2554	0.4816	0.085*
C5	0.17013 (13)	1.0757 (3)	0.4023 (3)	0.0605 (7)
H5A	0.1992	1.1160	0.3328	0.073*
C6	0.16698 (11)	0.9293 (2)	0.4174 (3)	0.0445 (6)
C7	0.20856 (11)	0.8339 (2)	0.3351 (2)	0.0450 (6)
H7A	0.2383	0.8693	0.2638	0.054*
C8	0.20641 (10)	0.6940 (2)	0.3568 (2)	0.0429 (6)
C9	0.15868 (11)	0.6355 (2)	0.4665 (3)	0.0460 (6)
C10	0.25260 (12)	0.5959 (3)	0.2770 (3)	0.0525 (6)
C11	−0.00432 (15)	0.9739 (3)	0.7994 (3)	0.0743 (8)
H11A	−0.0314	0.9150	0.8626	0.112*
H11B	−0.0349	1.0278	0.7362	0.112*
H11C	0.0237	1.0360	0.8592	0.112*
C12	0.33877 (13)	0.5785 (3)	0.0894 (3)	0.0697 (8)
H12A	0.3470	0.6224	−0.0059	0.084*
H12B	0.3189	0.4867	0.0709	0.084*
C13	0.40569 (13)	0.5629 (3)	0.1714 (3)	0.0646 (7)
H13A	0.4053	0.5142	0.2608	0.078*
C14	0.46490 (14)	0.6123 (3)	0.1279 (3)	0.0639 (7)
H14A	0.4640	0.6613	0.0386	0.077*
C15	0.53343 (12)	0.6000 (3)	0.2031 (3)	0.0560 (7)
C16	0.58725 (14)	0.6863 (3)	0.1617 (4)	0.0741 (9)
H16A	0.5804	0.7481	0.0830	0.089*
C17	0.65113 (15)	0.6830 (3)	0.2345 (5)	0.0831 (10)
H17A	0.6861	0.7445	0.2067	0.100*
C18	0.66314 (14)	0.5891 (3)	0.3481 (4)	0.0741 (9)
H18A	0.7059	0.5874	0.3980	0.089*
C19	0.61138 (15)	0.4981 (4)	0.3866 (3)	0.0763 (9)
H19A	0.6195	0.4320	0.4608	0.092*
C20	0.54716 (14)	0.5041 (3)	0.3158 (3)	0.0694 (8)
H20A	0.5123	0.4426	0.3443	0.083*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0600 (10)	0.0639 (11)	0.0597 (11)	0.0079 (9)	0.0171 (8)	−0.0059 (9)
O2	0.0487 (9)	0.0410 (9)	0.0494 (10)	0.0015 (7)	0.0053 (7)	−0.0008 (7)
O3	0.0869 (14)	0.0375 (10)	0.0877 (14)	0.0016 (9)	0.0227 (10)	0.0041 (9)
O4	0.1028 (16)	0.0562 (13)	0.1075 (17)	0.0296 (11)	0.0322 (13)	0.0052 (11)
O5	0.0522 (10)	0.0719 (12)	0.0615 (12)	0.0113 (9)	0.0125 (8)	−0.0069 (9)
C1	0.0391 (12)	0.0364 (12)	0.0486 (14)	0.0004 (10)	−0.0026 (10)	−0.0021 (10)
C2	0.0444 (13)	0.0505 (15)	0.0541 (15)	0.0053 (11)	−0.0019 (11)	−0.0051 (12)
C3	0.0668 (17)	0.0523 (16)	0.0767 (19)	0.0122 (13)	0.0061 (14)	−0.0112 (14)
C4	0.0784 (19)	0.0382 (14)	0.096 (2)	0.0072 (13)	0.0005 (17)	−0.0028 (15)
C5	0.0590 (16)	0.0446 (14)	0.0783 (19)	−0.0029 (12)	0.0079 (13)	0.0063 (13)
C6	0.0394 (12)	0.0392 (12)	0.0550 (15)	0.0021 (10)	−0.0010 (10)	−0.0012 (11)
C7	0.0370 (12)	0.0503 (14)	0.0477 (14)	−0.0026 (10)	0.0007 (9)	0.0011 (11)
C8	0.0364 (12)	0.0444 (13)	0.0476 (14)	0.0026 (10)	−0.0039 (10)	−0.0026 (10)
C9	0.0472 (13)	0.0401 (14)	0.0506 (15)	0.0028 (10)	−0.0024 (10)	−0.0044 (11)
C10	0.0470 (14)	0.0573 (16)	0.0531 (16)	0.0102 (12)	−0.0031 (11)	−0.0058 (13)
C11	0.0676 (18)	0.090 (2)	0.0663 (19)	0.0167 (16)	0.0152 (14)	−0.0173 (16)
C12	0.0520 (16)	0.093 (2)	0.0642 (18)	0.0203 (14)	0.0082 (13)	−0.0162 (16)
C13	0.0517 (15)	0.0826 (19)	0.0598 (17)	0.0113 (14)	0.0072 (12)	−0.0058 (15)
C14	0.0605 (16)	0.0681 (17)	0.0635 (17)	0.0112 (14)	0.0127 (13)	−0.0002 (14)
C15	0.0484 (14)	0.0513 (14)	0.0690 (18)	0.0042 (12)	0.0139 (12)	−0.0074 (13)
C16	0.0617 (18)	0.0521 (16)	0.109 (2)	0.0106 (14)	0.0295 (16)	0.0079 (16)
C17	0.0542 (18)	0.0535 (17)	0.143 (3)	−0.0068 (14)	0.0329 (18)	−0.012 (2)
C18	0.0490 (16)	0.078 (2)	0.096 (2)	0.0006 (15)	0.0078 (15)	−0.0310 (19)
C19	0.0669 (18)	0.091 (2)	0.071 (2)	0.0004 (17)	0.0080 (15)	0.0048 (16)
C20	0.0549 (16)	0.0741 (19)	0.080 (2)	−0.0136 (14)	0.0122 (14)	0.0070 (16)

Geometric parameters (Å, º) top

O1—C2	1.362 (3)	C11—H11A	0.9600
O1—C11	1.438 (3)	C11—H11B	0.9600
O2—C1	1.373 (3)	C11—H11C	0.9600
O2—C9	1.382 (3)	C12—C13	1.480 (4)
O3—C9	1.198 (3)	C12—H12A	0.9700
O4—C10	1.194 (3)	C12—H12B	0.9700
O5—C10	1.349 (3)	C13—C14	1.299 (4)
O5—C12	1.465 (3)	C13—H13A	0.9300
C1—C6	1.394 (3)	C14—C15	1.476 (4)
C1—C2	1.398 (3)	C14—H14A	0.9300
C2—C3	1.375 (4)	C15—C16	1.379 (3)
C3—C4	1.389 (4)	C15—C20	1.389 (4)
C3—H3A	0.9300	C16—C17	1.383 (4)
C4—C5	1.370 (4)	C16—H16A	0.9300
C4—H4A	0.9300	C17—C18	1.377 (4)
C5—C6	1.405 (3)	C17—H17A	0.9300
C5—H5A	0.9300	C18—C19	1.370 (4)
C6—C7	1.428 (3)	C18—H18A	0.9300
C7—C8	1.351 (3)	C19—C20	1.381 (4)
C7—H7A	0.9300	C19—H19A	0.9300
C8—C9	1.469 (3)	C20—H20A	0.9300
C8—C10	1.485 (3)

C2—O1—C11	116.7 (2)	H11A—C11—H11B	109.5
C1—O2—C9	122.93 (18)	O1—C11—H11C	109.5
C10—O5—C12	116.4 (2)	H11A—C11—H11C	109.5
O2—C1—C6	121.0 (2)	H11B—C11—H11C	109.5
O2—C1—C2	117.3 (2)	O5—C12—C13	111.3 (2)
C6—C1—C2	121.7 (2)	O5—C12—H12A	109.4
O1—C2—C3	126.0 (2)	C13—C12—H12A	109.4
O1—C2—C1	116.1 (2)	O5—C12—H12B	109.4
C3—C2—C1	117.9 (2)	C13—C12—H12B	109.4
C2—C3—C4	121.3 (3)	H12A—C12—H12B	108.0
C2—C3—H3A	119.4	C14—C13—C12	124.9 (3)
C4—C3—H3A	119.4	C14—C13—H13A	117.6
C5—C4—C3	120.9 (2)	C12—C13—H13A	117.6
C5—C4—H4A	119.6	C13—C14—C15	127.8 (3)
C3—C4—H4A	119.6	C13—C14—H14A	116.1
C4—C5—C6	119.5 (2)	C15—C14—H14A	116.1
C4—C5—H5A	120.3	C16—C15—C20	117.2 (3)
C6—C5—H5A	120.3	C16—C15—C14	119.8 (3)
C1—C6—C5	118.8 (2)	C20—C15—C14	123.0 (2)
C1—C6—C7	117.2 (2)	C15—C16—C17	121.5 (3)
C5—C6—C7	124.0 (2)	C15—C16—H16A	119.2
C8—C7—C6	122.5 (2)	C17—C16—H16A	119.2
C8—C7—H7A	118.7	C18—C17—C16	120.2 (3)
C6—C7—H7A	118.7	C18—C17—H17A	119.9
C7—C8—C9	119.6 (2)	C16—C17—H17A	119.9
C7—C8—C10	122.2 (2)	C19—C18—C17	119.2 (3)
C9—C8—C10	118.1 (2)	C19—C18—H18A	120.4
O3—C9—O2	115.8 (2)	C17—C18—H18A	120.4
O3—C9—C8	127.6 (2)	C18—C19—C20	120.3 (3)
O2—C9—C8	116.62 (19)	C18—C19—H19A	119.9
O4—C10—O5	123.1 (2)	C20—C19—H19A	119.9
O4—C10—C8	125.8 (3)	C19—C20—C15	121.5 (3)
O5—C10—C8	111.2 (2)	C19—C20—H20A	119.3
O1—C11—H11A	109.5	C15—C20—H20A	119.3
O1—C11—H11B	109.5

C9—O2—C1—C6	4.0 (3)	C7—C8—C9—O3	−179.1 (2)
C9—O2—C1—C2	−174.71 (19)	C10—C8—C9—O3	−1.1 (3)
C11—O1—C2—C3	2.6 (4)	C7—C8—C9—O2	1.1 (3)
C11—O1—C2—C1	−177.7 (2)	C10—C8—C9—O2	179.11 (18)
O2—C1—C2—O1	−0.4 (3)	C12—O5—C10—O4	−1.3 (3)
C6—C1—C2—O1	−179.15 (19)	C12—O5—C10—C8	178.20 (18)
O2—C1—C2—C3	179.3 (2)	C7—C8—C10—O4	172.9 (3)
C6—C1—C2—C3	0.6 (3)	C9—C8—C10—O4	−5.0 (4)
O1—C2—C3—C4	179.8 (2)	C7—C8—C10—O5	−6.5 (3)
C1—C2—C3—C4	0.0 (4)	C9—C8—C10—O5	175.55 (18)
C2—C3—C4—C5	−0.1 (4)	C10—O5—C12—C13	−83.6 (3)
C3—C4—C5—C6	−0.5 (4)	O5—C12—C13—C14	−115.1 (3)
O2—C1—C6—C5	−179.8 (2)	C12—C13—C14—C15	−179.5 (3)
C2—C1—C6—C5	−1.2 (3)	C13—C14—C15—C16	−164.1 (3)
O2—C1—C6—C7	−1.3 (3)	C13—C14—C15—C20	15.9 (4)
C2—C1—C6—C7	177.37 (19)	C20—C15—C16—C17	−3.4 (4)
C4—C5—C6—C1	1.1 (4)	C14—C15—C16—C17	176.6 (3)
C4—C5—C6—C7	−177.4 (2)	C15—C16—C17—C18	2.2 (4)
C1—C6—C7—C8	−1.3 (3)	C16—C17—C18—C19	0.7 (4)
C5—C6—C7—C8	177.1 (2)	C17—C18—C19—C20	−2.3 (4)
C6—C7—C8—C9	1.4 (3)	C18—C19—C20—C15	0.9 (4)
C6—C7—C8—C10	−176.50 (19)	C16—C15—C20—C19	1.9 (4)
C1—O2—C9—O3	176.3 (2)	C14—C15—C20—C19	−178.2 (3)
C1—O2—C9—C8	−3.8 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4A···O3ⁱ	0.93	2.51	3.429 (3)	170
C17—H17A···O4ⁱⁱ	0.93	2.44	3.294 (4)	153

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

Experimental details

Crystal data
Chemical formula	C₂₀H₁₆O₅
M_r	336.33
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	19.226 (4), 9.5483 (19), 9.0046 (18)
β (°)	90.97 (3)
V (Å³)	1652.8 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.20 × 0.17 × 0.17

Data collection
Diffractometer	Bruker SMART CCD area detector
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	4903, 2834, 2157
R_int	0.053
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.065, 0.155, 1.15
No. of reflections	2834
No. of parameters	228
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.24, −0.20

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4A···O3ⁱ	0.93	2.51	3.429 (3)	170
C17—H17A···O4ⁱⁱ	0.93	2.44	3.294 (4)	153

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

Acknowledgements

This work was supported by the Natural Science Foundation of Henan Province (No. 2009 A150012).

References

Bruker (2007). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Finn, G. J., Creaven, B. S. & Egan, D. A. (2004). Cancer Lett. 214, 43–54. Web of Science CrossRef PubMed CAS Google Scholar
Hoult, J. R. R. & Paya, M. (1996). Gen. Pharmacol. 27, 713–722. CrossRef CAS PubMed Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yu, D., Morris-Natschke, S. L. & Lee, K.-H. (2007). Med. Res. Rev. 27, 108–132. Web of Science CrossRef PubMed CAS Google Scholar
Yu, D., Suzuki, M., Xie, L., Susan, L., Morris-Natschke, S. L. & Lee, K.-H. (2003). Med. Res. Rev. 23, 322–345. Web of Science CrossRef PubMed CAS Google Scholar