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Acta Crystallogr Sect E Struct Rep Online. 2010 August 1; 66(Pt 8): o2082–o2083.
Published online 2010 July 21. doi:  10.1107/S1600536810028394
PMCID: PMC3007383

Vadimezan: 2-(5,6-dimethyl-9-oxo-9H-xanthen-4-yl)acetic acid

Abstract

In the title mol­ecule, C17H14O4, the C atom of the carboxyl group deviates by 1.221 (3) Å from the plane [maximum deviation = 0.0122(2) Å] of the tricycic ring system. In the crystal structure, inter­molecular O—H(...)O hydrogen bonds link the mol­ecules into centrosymmetric dimers, and π–π inter­actions [centroid–centroid distances = 3.491 (3), 3.591 (3), 3.639 (3) and 3.735 (3) Å] link these dimers into layers parallel to the ac plane. Weak inter­molecular C—H(...)O inter­actions further consolidate the crystal packing.

Related literature

For general background to and recent reviews of vascular-disrupting agents and the development of Vadimezan (DMXAA, ASA404), a promising small-mol­ecule tumor-vascular disrupting agent in phase III clinical trials, see: McKeage & Baguley (2010 [triangle]); Head & Jameson (2010 [triangle]); Ching (2008 [triangle]); Patterson & Rustin (2007 [triangle]); Hinnen & Eskens (2007 [triangle]); Lippert (2007 [triangle]). For a recent clinical study of Vadimezan, see: Pili et al. (2010 [triangle]); McKeage et al. (2008 [triangle], 2009 [triangle]). For studies of the mol­ecular mechanisms and signal pathways of Vadimezan, see: Zhan et al. (2010 [triangle]); Cheng et al. (2010 [triangle]); Roberts et al. (2008 [triangle]). For the biological and pharmacological activity of Vadimezan analogues with structure–activity relationships, see: Gobbi et al. (2006 [triangle]); Woon et al. (2005 [triangle]). For the synthesis and spectroscopic data for Vadimezan, see: Yang & Denny (2009 [triangle]); Atwell et al. (2002 [triangle]). For related xanthone structures, see: Yu et al. (2008 [triangle]); Zhang et al. (2007 [triangle]).

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Object name is e-66-o2082-scheme1.jpg

Experimental

Crystal data

  • C17H14O4
  • M r = 282.28
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-o2082-efi1.jpg
  • a = 6.7854 (19) Å
  • b = 9.826 (3) Å
  • c = 10.532 (3) Å
  • α = 71.435 (7)°
  • β = 82.741 (9)°
  • γ = 83.142 (9)°
  • V = 658.0 (3) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.10 mm−1
  • T = 163 K
  • 0.50 × 0.50 × 0.37 mm

Data collection

  • Rigaku AFC10/Saturn724+ diffractometer
  • 6284 measured reflections
  • 2955 independent reflections
  • 2304 reflections with I > 2σ(I)
  • R int = 0.018

Refinement

  • R[F 2 > 2σ(F 2)] = 0.040
  • wR(F 2) = 0.094
  • S = 1.00
  • 2955 reflections
  • 195 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.26 e Å−3
  • Δρmin = −0.17 e Å−3

Data collection: CrystalClear (Rigaku/MSC, 2008 [triangle]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXL97 (Sheldrick, 2008 [triangle]); software used to prepare material for publication: publCIF (Westrip, 2010 [triangle]) and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810028394/cv2747sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810028394/cv2747Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors acknowledge financial support from Hangzhou Minsheng Pharmaceutical Group Co Ltd, Hangzhou, People’s Republic of China. The data collection was carried out by Professor Kai-Bei Yu at the State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology.

supplementary crystallographic information

Comment

Tumor vascular disrupting agents (VDA) cause the established vascular structure inside a solid tumor to collapse, depriving the tumor of blood, oxygen and nutrients it needs to survive (McKeage et al., 2010; Head et al., 2010; Ching, 2008; Patterson et al., 2007; Hinnen et al., 2007; Lippert, 2007). A number of new drug-based VDAs have been developed that are believed to be highly efficient, low toxic, and several of them are currently undergoing clinical trials, among which Vadimezan is the most advanced in Phase III clinical development (Pili et al., 2010; McKeage et al., 2009; McKeage et al., 2008). The study of antitumor mechanisms and signal pathways of Vadimezan is carried out (Zhan et al., 2010; Cheng et al., 2010; Roberts et al., 2008), as well as the structure modification of xanthones (Gobbi et al., 2006; Woon et al., 2005).

The molecular structure of Vadimezan is very important and necessary in understanding of the compound and may help to further elucidate its antivascular effect for the treatment of human cancer. Its crystal structure is reported for the first time in this paper. The structure (Figure 1) is similar to other xanthones reported with an essential planar three-ring skeleton and the C atom of the carboxyl group deviates at 1.221 (3) Å from the tricycle plane. In the crystal structure, intermolecular O—H···O (Table 2) hydrogen bonds link the molecules into centrosymmetric dimers, and π-π interactions (Table 1) link these dimers into layers parallel to ac plane. Weak intermolecular C—H···O interactions (Table 2) consolidate further the crystal packing (Fig. 2).

Experimental

Vadimezan was prepared from 3,4-dimethylanthranilic acid according to literature method (Atwell et al., 2002). Diazotization of 3,4-dimethylanthranilic acid with NaNO2 and then treatment with KI led to 3,4-dimethyl-2-iodobenzoic acid, which was coupled with 2-hydroxyphenylacetic acid catalyzed by TDA-1 and Cu(I) in dried DMSO to obtain 2-[2-(carboxylmethyl)phenoxy]-3,4-dimethylbenzoic acid. Finally, ring closure in sulfuric acid led to 5,6-dimethyl-9-oxoxanthene-4-acetic acid: white solid; mp: 529–532 K; PHPLC 98.2%; IR νmax (KBr)/cm-1: 2970, 1708, 1650, 1602, 1411, 1330, 1212, 768; 1H NMR (DMSO-d6, 500 MHz) δ: 12.60 (s, 1H, COOH), 8.07 (dd, J1 = 1.5 Hz, J2 = 8.0 Hz, 1H, Ar), 7.89 (d, J = 8.0 Hz, 1H, Ar), 7.78 (dd, J1 = 1.3 Hz, J2 = 7.3 Hz, 1H, Ar), 7.40 (t, J = 7.5 Hz, 1H, Ar), 7.24 (d, J = 8.5 Hz, 1H, Ar), 3.95 (s, 2H, Ar—CH2), 2.39 (s, 3H, Ar—CH3), 2.36 (s, 3H, Ar—CH3); EIMS m/z(%): 282(M+, 77), 238 (42), 237 (100), 236 (26), 223 (17), 209 (37), 195 (12), 165 (28).

Refinement

H atom attached to carboxyl O atom was located in a difference map and refined with bond restraint O—H = 1.00 (2) Å. C-bound H atoms were positioned geometrically (C—H 0.95 - 0.99 Å). All H atoms were refined as riding, with Uiso(H) = 1.2 - 1.5 Ueq of the parent atoms. Hydrogen atoms attached to C14 are disordered with a refined site occupancy factor 0.50 for each H14A, H14B, H14C, H14D, H14E and H14F.

Figures

Fig. 1.
The molecular structure of (I) shown with 30% probability displacement ellipsoids. One component of rotationally disordered methyl group (C14) is shown.
Fig. 2.
A portion of the packing diagram of (I) showing intermolecular hydrogen bonds as dashed lines.

Crystal data

C17H14O4Z = 2
Mr = 282.28F(000) = 296
Triclinic, P1Dx = 1.425 Mg m3
a = 6.7854 (19) ÅMo Kα radiation, λ = 0.71073 Å
b = 9.826 (3) ÅCell parameters from 1944 reflections
c = 10.532 (3) Åθ = 3.0–27.5°
α = 71.435 (7)°µ = 0.10 mm1
β = 82.741 (9)°T = 163 K
γ = 83.142 (9)°Block, colorless
V = 658.0 (3) Å30.50 × 0.50 × 0.37 mm

Data collection

Rigaku AFC10/Saturn724+ diffractometer2304 reflections with I > 2σ(I)
Radiation source: Rotating AnodeRint = 0.018
graphiteθmax = 27.5°, θmin = 3.4°
Detector resolution: 28.5714 pixels mm-1h = −8→8
phi and ω scansk = −11→12
6284 measured reflectionsl = −13→13
2955 independent reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.040Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.094H atoms treated by a mixture of independent and constrained refinement
S = 1.00w = 1/[σ2(Fo2) + (0.0346P)2 + 0.226P] where P = (Fo2 + 2Fc2)/3
2955 reflections(Δ/σ)max < 0.001
195 parametersΔρmax = 0.26 e Å3
0 restraintsΔρmin = −0.17 e Å3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > 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)

xyzUiso*/UeqOcc. (<1)
O10.21097 (13)0.40487 (9)0.72385 (9)0.0215 (2)
O20.36821 (16)0.20951 (10)0.43040 (10)0.0335 (3)
O30.49314 (15)0.35197 (11)0.95899 (10)0.0312 (2)
O40.23835 (16)0.47712 (12)1.03729 (11)0.0361 (3)
C10.3402 (2)0.03641 (14)0.70661 (15)0.0278 (3)
H10.3796−0.01440.64310.033*
C20.3195 (2)−0.03755 (15)0.84129 (16)0.0330 (3)
H20.3434−0.13950.87100.040*
C30.2632 (2)0.03676 (15)0.93484 (15)0.0306 (3)
H30.2494−0.01591.02790.037*
C40.2271 (2)0.18497 (14)0.89551 (14)0.0252 (3)
C50.18653 (18)0.63568 (13)0.56645 (13)0.0208 (3)
C60.20182 (18)0.72389 (13)0.43318 (13)0.0221 (3)
C70.25597 (19)0.66243 (14)0.32918 (13)0.0248 (3)
H70.26640.72330.23860.030*
C80.29413 (19)0.51639 (14)0.35551 (13)0.0238 (3)
H80.33010.47720.28330.029*
C90.32191 (19)0.26831 (14)0.51829 (13)0.0232 (3)
C100.30347 (19)0.18691 (14)0.66213 (13)0.0223 (3)
C110.24803 (18)0.25830 (13)0.75729 (13)0.0212 (3)
C120.22678 (17)0.48664 (13)0.59068 (12)0.0188 (3)
C130.28044 (18)0.42500 (13)0.48780 (13)0.0202 (3)
C140.1303 (2)0.69521 (15)0.68242 (14)0.0298 (3)
H14A0.12790.61590.76710.036*0.50
H14B−0.00200.74770.67340.036*0.50
H14C0.22840.76080.68230.036*0.50
H14D0.10840.80040.64810.036*0.50
H14E0.23820.66860.74180.036*0.50
H14F0.00780.65540.73300.036*0.50
C150.1628 (2)0.88493 (14)0.39994 (15)0.0291 (3)
H15A0.02750.90870.43620.035*
H15B0.17610.92920.30210.035*
H15C0.25940.92170.43990.035*
C160.1661 (2)0.26804 (15)0.99384 (14)0.0293 (3)
H16A0.14620.19911.08540.035*
H16B0.03690.32400.97200.035*
C170.3156 (2)0.36947 (15)0.99384 (13)0.0260 (3)
H4O0.345 (3)0.541 (2)1.032 (2)0.076 (7)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0261 (5)0.0176 (4)0.0205 (5)−0.0008 (3)−0.0016 (4)−0.0061 (4)
O20.0449 (6)0.0277 (5)0.0326 (6)0.0000 (4)−0.0035 (5)−0.0171 (4)
O30.0298 (5)0.0314 (5)0.0339 (6)0.0002 (4)−0.0023 (4)−0.0133 (4)
O40.0322 (6)0.0397 (6)0.0430 (6)0.0003 (5)−0.0014 (5)−0.0241 (5)
C10.0279 (7)0.0212 (7)0.0377 (8)−0.0008 (5)−0.0081 (6)−0.0125 (6)
C20.0367 (8)0.0185 (7)0.0426 (9)−0.0008 (6)−0.0115 (7)−0.0053 (6)
C30.0334 (8)0.0252 (7)0.0295 (7)−0.0046 (6)−0.0071 (6)−0.0010 (6)
C40.0227 (7)0.0253 (7)0.0272 (7)−0.0041 (5)−0.0031 (5)−0.0063 (6)
C50.0184 (6)0.0207 (6)0.0249 (7)−0.0018 (5)−0.0017 (5)−0.0094 (5)
C60.0185 (6)0.0198 (6)0.0279 (7)−0.0021 (5)−0.0036 (5)−0.0063 (5)
C70.0239 (7)0.0266 (7)0.0215 (7)−0.0030 (5)−0.0030 (5)−0.0034 (5)
C80.0233 (7)0.0278 (7)0.0226 (7)−0.0029 (5)−0.0016 (5)−0.0108 (5)
C90.0211 (6)0.0232 (7)0.0290 (7)−0.0019 (5)−0.0038 (5)−0.0127 (6)
C100.0197 (6)0.0206 (6)0.0287 (7)−0.0021 (5)−0.0052 (5)−0.0089 (5)
C110.0185 (6)0.0179 (6)0.0273 (7)−0.0024 (5)−0.0042 (5)−0.0060 (5)
C120.0159 (6)0.0199 (6)0.0206 (6)−0.0030 (5)−0.0019 (5)−0.0058 (5)
C130.0175 (6)0.0209 (6)0.0241 (7)−0.0025 (5)−0.0030 (5)−0.0089 (5)
C140.0385 (8)0.0228 (7)0.0289 (7)−0.0018 (6)0.0008 (6)−0.0108 (6)
C150.0318 (8)0.0218 (7)0.0317 (8)−0.0016 (5)−0.0032 (6)−0.0053 (6)
C160.0307 (7)0.0295 (7)0.0246 (7)−0.0036 (6)0.0015 (6)−0.0053 (6)
C170.0320 (7)0.0270 (7)0.0165 (6)0.0022 (6)−0.0036 (5)−0.0045 (5)

Geometric parameters (Å, °)

O1—C111.3690 (15)C7—C81.3708 (19)
O1—C121.3746 (15)C7—H70.9500
O2—C91.2301 (15)C8—C131.3953 (18)
O3—C171.2225 (17)C8—H80.9500
O4—C171.3108 (16)C9—C101.4680 (19)
O4—H4O1.00 (2)C9—C131.4688 (18)
C1—C21.370 (2)C10—C111.3883 (18)
C1—C101.4032 (18)C12—C131.3925 (17)
C1—H10.9500C14—H14A0.9800
C2—C31.395 (2)C14—H14B0.9800
C2—H20.9500C14—H14C0.9800
C3—C41.3816 (19)C14—H14D0.9800
C3—H30.9500C14—H14E0.9800
C4—C111.4011 (19)C14—H14F0.9800
C4—C161.5030 (19)C15—H15A0.9800
C5—C61.3937 (18)C15—H15B0.9800
C5—C121.4031 (17)C15—H15C0.9800
C5—C141.5045 (18)C16—C171.505 (2)
C6—C71.4021 (19)C16—H16A0.9900
C6—C151.5057 (18)C16—H16B0.9900
Cg1···Cg2i3.491 (3)Cg2···Cg2i3.735 (3)
Cg1···Cg2ii3.591 (3)Cg2···Cg2ii3.639 (3)
C11—O1—C12119.45 (10)C12—C13—C9120.73 (12)
C17—O4—H4O109.3 (12)C8—C13—C9121.21 (11)
C2—C1—C10120.21 (13)C5—C14—H14A109.5
C2—C1—H1119.9C5—C14—H14B109.5
C10—C1—H1119.9H14A—C14—H14B109.5
C1—C2—C3120.06 (13)C5—C14—H14C109.5
C1—C2—H2120.0H14A—C14—H14C109.5
C3—C2—H2120.0H14B—C14—H14C109.5
C4—C3—C2121.64 (13)C5—C14—H14D109.5
C4—C3—H3119.2H14A—C14—H14D141.1
C2—C3—H3119.2H14B—C14—H14D56.3
C3—C4—C11117.33 (12)H14C—C14—H14D56.3
C3—C4—C16122.88 (13)C5—C14—H14E109.5
C11—C4—C16119.79 (12)H14A—C14—H14E56.3
C6—C5—C12117.71 (11)H14B—C14—H14E141.1
C6—C5—C14122.29 (11)H14C—C14—H14E56.3
C12—C5—C14120.00 (12)H14D—C14—H14E109.5
C5—C6—C7119.79 (12)C5—C14—H14F109.5
C5—C6—C15120.53 (11)H14A—C14—H14F56.3
C7—C6—C15119.67 (12)H14B—C14—H14F56.3
C8—C7—C6121.37 (12)H14C—C14—H14F141.1
C8—C7—H7119.3H14D—C14—H14F109.5
C6—C7—H7119.3H14E—C14—H14F109.5
C7—C8—C13120.32 (12)C6—C15—H15A109.5
C7—C8—H8119.8C6—C15—H15B109.5
C13—C8—H8119.8H15A—C15—H15B109.5
O2—C9—C10122.46 (12)C6—C15—H15C109.5
O2—C9—C13122.77 (12)H15A—C15—H15C109.5
C10—C9—C13114.77 (11)H15B—C15—H15C109.5
C11—C10—C1118.59 (12)C4—C16—C17113.59 (11)
C11—C10—C9120.20 (11)C4—C16—H16A108.8
C1—C10—C9121.21 (12)C17—C16—H16A108.8
O1—C11—C10122.88 (12)C4—C16—H16B108.8
O1—C11—C4114.95 (11)C17—C16—H16B108.8
C10—C11—C4122.17 (12)H16A—C16—H16B107.7
O1—C12—C13121.97 (11)O3—C17—O4123.02 (14)
O1—C12—C5115.28 (11)O3—C17—C16123.28 (12)
C13—C12—C5122.75 (12)O4—C17—C16113.68 (12)
C12—C13—C8118.06 (11)
C10—C1—C2—C3−0.5 (2)C16—C4—C11—O10.55 (18)
C1—C2—C3—C40.0 (2)C3—C4—C11—C10−0.25 (19)
C2—C3—C4—C110.4 (2)C16—C4—C11—C10−179.84 (12)
C2—C3—C4—C16179.95 (13)C11—O1—C12—C13−0.27 (17)
C12—C5—C6—C7−0.03 (18)C11—O1—C12—C5−179.83 (11)
C14—C5—C6—C7179.62 (12)C6—C5—C12—O1179.53 (11)
C12—C5—C6—C15−179.37 (12)C14—C5—C12—O1−0.13 (17)
C14—C5—C6—C150.28 (19)C6—C5—C12—C13−0.03 (19)
C5—C6—C7—C80.2 (2)C14—C5—C12—C13−179.69 (12)
C15—C6—C7—C8179.51 (12)O1—C12—C13—C8−179.58 (11)
C6—C7—C8—C13−0.2 (2)C5—C12—C13—C8−0.05 (19)
C2—C1—C10—C110.6 (2)O1—C12—C13—C90.23 (18)
C2—C1—C10—C9−179.11 (13)C5—C12—C13—C9179.75 (11)
O2—C9—C10—C11−179.09 (12)C7—C8—C13—C120.19 (19)
C13—C9—C10—C110.80 (17)C7—C8—C13—C9−179.61 (12)
O2—C9—C10—C10.6 (2)O2—C9—C13—C12179.41 (12)
C13—C9—C10—C1−179.46 (12)C10—C9—C13—C12−0.47 (17)
C12—O1—C11—C100.62 (17)O2—C9—C13—C8−0.8 (2)
C12—O1—C11—C4−179.77 (11)C10—C9—C13—C8179.32 (11)
C1—C10—C11—O1179.34 (12)C3—C4—C16—C17116.51 (15)
C9—C10—C11—O1−0.91 (19)C11—C4—C16—C17−63.93 (17)
C1—C10—C11—C4−0.24 (19)C4—C16—C17—O3−25.38 (19)
C9—C10—C11—C4179.51 (12)C4—C16—C17—O4155.89 (12)
C3—C4—C11—O1−179.87 (11)

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

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O4—H4O···O3iii1.00 (2)1.63 (2)2.633 (1)173.25 (2)
C16—H16B···O4iv0.992.523.460 (1)158 (1)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CV2747).

References

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