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ISSN: 2056-9890

4-Eth­oxy­imino-N′-meth­oxy­pyrrolidin-1-ium-3-carboximidamidium dichloride

aInstitute of Medicinal Biotechnology, Chinese Academy of Medical Sciences, and Peking Union Medical College, Beijing 100050, People's Republic of China
*Correspondence e-mail: lmllyx@yahoo.com.cn

(Received 11 January 2009; accepted 10 February 2009; online 21 February 2009)

The title compound, C8H18N4O22+·2Cl, contains two oxime groups. The methyl oxime group has a Z configuration, and the ethyl oxime group is disordered, with both Z and E configurations in occupancies of 0.840 (8) and 0.160 (8), respectively. In the crystal structure, there are a number of N—H⋯Cl hydrogen bonds.

Related literature

For properties of quinolone derivatives, see: Ball et al. (1998[Ball, P., Tilloston, G. & Fernald, A. (1998). Expert Opin. Investig. Drugs, 7, 761-783.]); Ray et al. (2005[Ray, S., Pathak, S. R. & Chaturvedi, D. (2005). Drugs Future, 30, 161-180.]). For the synthesis of new quinolones, see: Anderson & Osheroff (2001[Anderson, V. E. & Osheroff, N. (2001). Curr. Pharm. Des. 7, 337-353.]); Choi et al. (2004[Choi, D. R., Shin, J. H. & Yang, J. (2004). Bioorg. Med. Chem. Lett. 14, 1273-1277.]); Wang, Guo et al. (2008[Wang, X. Y., Guo, Q. & Wang, Y. C. (2008). Acta Pharmacol. Sin. 43, 819-827.]). For some crystal structures of quinolones, see: Wang, Liu et al. (2008[Wang, J., Liu, M., Cao, J. & Wang, Y. (2008). Acta Cryst. E64, o2294.]).

[Scheme 1]

Experimental

Crystal data
  • C8H18N4O22+·2Cl

  • Mr = 273.16

  • Orthorhombic, P b c n

  • a = 12.7355 (14) Å

  • b = 8.8506 (12) Å

  • c = 26.334 (2) Å

  • V = 2968.3 (6) Å3

  • Z = 8

  • Mo Kα radiation

  • μ = 0.43 mm−1

  • T = 298 K

  • 0.23 × 0.20 × 0.19 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.907, Tmax = 0.922

  • 14370 measured reflections

  • 2597 independent reflections

  • 1986 reflections with I > 2σ(I)

  • Rint = 0.062

Refinement
  • R[F2 > 2σ(F2)] = 0.077

  • wR(F2) = 0.210

  • S = 1.08

  • 2597 reflections

  • 170 parameters

  • H-atom parameters constrained

  • Δρmax = 0.44 e Å−3

  • Δρmin = −0.33 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N3—H3B⋯Cl1 0.86 2.29 3.144 (4) 173
N3—H3A⋯Cl1i 0.86 2.41 3.213 (4) 156
N2—H2⋯Cl2ii 0.86 2.21 3.029 (4) 160
N1—H1B⋯Cl2 0.90 2.18 3.035 (4) 159
N1—H1A⋯Cl1iii 0.90 2.20 3.076 (4) 165
Symmetry codes: (i) [-x+{\script{3\over 2}}, y+{\script{1\over 2}}, z]; (ii) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]; (iii) -x+1, -y, -z+1.

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 1999[Bruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Since the discovery of norfloxacin, fluoroquinolone antibacterial agents have emerged as one of the dominant classes of chemotherapeutic drugs for the treatment of various bacterial infections (Ball et al., 1998; Ray et al., 2005). The most intensive structural variations have been carried out on the basic group at the C-7 position. In general, 5- and 6-membered nitrogen heterocycles including piperazinyl, pyrrolidinyl and piperidinyl type side chains have been proven to be the optimal substituents, as evidenced by the compounds currently on the market (Anderson & Osheroff, 2001; Choi et al., 2004). Recently, as part of an ongoing program to find potent new fluoroquinolones displaying strong Gram-positive activity, we have focused our attention on introducing new functional groups to the pyrrolidine ring. We report here the crystal structure of the title compound, which is intended for use as a novel substituent at the C-7 position of fluoroquinolones.

There are two oximes in the molecule of the title compound (Fig. 1). The methyloxime has the Z configuration, and the ethyloxime is disordered, with both Z and E configurations at occupancy factors of 0.840 (8) and 0.160 (8), respectively. In the molecule the N3—C5(1.296 (6) Å) bond length is significantly shorter than the normal C—N single bond (1.47 Å), indicating some delocalization over the N3-C5-N2 group. The five-membered pyrrolidine ring adopts an envelope conformation. In the crystal structure, there are a number of N–H···Cl hydrogen bonds. (Table 1)

Related literature top

For properties of quinolone derivatives, see: Ball et al. (1998); Ray et al. (2005). For the synthesis of new quinolones, see: Anderson & Osheroff (2001); Choi et al. (2004); Wang, Guo et al. (2008). For some crystal structures of quinolones, see: Wang, Liu et al. (2008).

Experimental top

To a stirring solution of N'-methoxy-(1-N-tert-butoxycarbonyl-4- ethoxyimino) pyrrolidine-3-carboximidamide (15.0 g, 50.0 mmol) in methanol (80 ml) was pumped into dry hydrogen chloride for 2 h at room temperature. After the removal of the methanol under reduced pressure, the residue was treated with ethyl acetate (80 ml), and filtered. The filter cake was washed with ethyl acetate and ether, respectively, dried in vacuo to give the title compound as a white solid (11.5 g, 84.2%; mp: 375–376 K). Single crystals suitable for X-ray analysis were obtained by slow evaporation of a methanol/ ethyl acetate (1:1 v/v). 1H NMR(DMSO-d6, δ):1.14–1.17(3H, m, CH3), 3.44–3.58(m, 1H, pyrrolidine), 3.53(2H, br, NH2+), 3.66(3H, s, OCH3), 3.68–3.79(2H, m, OCH2), 4.03–4.11(4H, m, pyrrolidine), 9.88–9.93(3H, br, NH2, NH+). MS(ESI, m/z): 201(M+H)+.

Refinement top

All H atoms were placed at calculated positions, with C—H = 0.96–0.97 Å, N—H= 0.86–0.90 Å, and included in the final cycles of refinement using a riding model, with Uiso(H) = 1.2Ueq(C, N) or 1.5Ueq(C) for methyl H atoms.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999) and SHELXTL (Sheldrick, 2008); 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
[Figure 1] Fig. 1. The molecular structure showing 40% probability displacement ellipsoids and the atom-numbering scheme.
[Figure 2] Fig. 2. Crystal packing of the title compound viewed down the b axis.
4-Ethoxyimino-N'-methoxypyrrolidin-1-ium-3-carboximidamidium dichloride top
Crystal data top
C8H18N4O22+·2ClF(000) = 1152
Mr = 273.16Dx = 1.223 Mg m3
Orthorhombic, PbcnMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2n 2abCell parameters from 3944 reflections
a = 12.7355 (14) Åθ = 2.2–24.1°
b = 8.8506 (12) ŵ = 0.43 mm1
c = 26.334 (2) ÅT = 298 K
V = 2968.3 (6) Å3Block, colorless
Z = 80.23 × 0.20 × 0.19 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
2597 independent reflections
Radiation source: fine-focus sealed tube1986 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.062
ϕ and ω scansθmax = 25.0°, θmin = 1.6°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1514
Tmin = 0.907, Tmax = 0.922k = 1010
14370 measured reflectionsl = 2931
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.077Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.210H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.0819P)2 + 7.7771P]
where P = (Fo2 + 2Fc2)/3
2597 reflections(Δ/σ)max = 0.001
170 parametersΔρmax = 0.44 e Å3
0 restraintsΔρmin = 0.33 e Å3
Crystal data top
C8H18N4O22+·2ClV = 2968.3 (6) Å3
Mr = 273.16Z = 8
Orthorhombic, PbcnMo Kα radiation
a = 12.7355 (14) ŵ = 0.43 mm1
b = 8.8506 (12) ÅT = 298 K
c = 26.334 (2) Å0.23 × 0.20 × 0.19 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
2597 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1986 reflections with I > 2σ(I)
Tmin = 0.907, Tmax = 0.922Rint = 0.062
14370 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0770 restraints
wR(F2) = 0.210H-atom parameters constrained
S = 1.08Δρmax = 0.44 e Å3
2597 reflectionsΔρmin = 0.33 e Å3
170 parameters
Special details top

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) top
xyzUiso*/UeqOcc. (<1)
Cl10.67028 (9)0.08761 (14)0.52171 (5)0.0516 (4)
Cl20.18814 (10)0.22720 (17)0.63480 (6)0.0636 (5)
N10.3711 (3)0.1103 (5)0.57222 (17)0.0528 (11)
H1A0.36400.03820.54840.063*
H1B0.30900.12200.58810.063*
N20.5131 (3)0.5960 (4)0.59228 (17)0.0543 (11)
H20.45900.61730.61050.065*
N30.6142 (3)0.4217 (5)0.55190 (18)0.0573 (12)
H3A0.65930.48970.54370.069*
H3B0.62390.32930.54290.069*
N40.559 (2)0.2442 (19)0.6611 (11)0.065 (4)0.840 (8)
N4'0.570 (12)0.212 (14)0.657 (6)0.065 (4)0.160 (8)
O10.5835 (3)0.7083 (4)0.57752 (15)0.0579 (10)
O20.5905 (4)0.1079 (6)0.6834 (2)0.0762 (17)0.840 (8)
O2'0.581 (2)0.352 (3)0.6806 (10)0.071 (8)0.160 (8)
C10.4045 (4)0.2533 (6)0.5489 (2)0.0503 (12)
H1C0.34510.30660.53430.060*
H1D0.45640.23590.52260.060*
C20.4513 (4)0.3417 (5)0.59299 (19)0.0446 (11)
H2A0.39440.39200.61150.053*
C30.4953 (4)0.2171 (5)0.62580 (18)0.0454 (11)
C40.4533 (4)0.0679 (6)0.6089 (2)0.0545 (13)
H4A0.50750.00760.59290.065*
H4B0.42400.01190.63720.065*
C50.5316 (4)0.4584 (5)0.57781 (19)0.0443 (11)
C60.6473 (6)0.7496 (7)0.6196 (3)0.0761 (18)
H6A0.60360.78520.64680.091*
H6B0.69490.82830.60960.091*
H6C0.68660.66330.63090.091*
C70.6511 (8)0.1432 (11)0.7286 (3)0.089 (3)0.840 (8)
H7A0.61040.20540.75170.106*0.840 (8)
H7B0.71490.19700.71970.106*0.840 (8)
C80.6770 (12)0.0062 (15)0.7528 (5)0.142 (5)0.840 (8)
H8A0.61310.05800.76130.171*0.840 (8)
H8B0.71740.01050.78300.171*0.840 (8)
H8C0.71690.06650.72940.171*0.840 (8)
C7'0.648 (4)0.337 (6)0.7247 (18)0.089 (3)0.160 (8)
H7'10.69340.24880.72140.106*0.160 (8)
H7'20.60720.32740.75550.106*0.160 (8)
C8'0.713 (6)0.482 (7)0.725 (2)0.12 (2)0.160 (8)
H8'10.75920.48220.75410.148*0.160 (8)
H8'20.66730.56800.72700.148*0.160 (8)
H8'30.75450.48840.69470.148*0.160 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0413 (7)0.0468 (7)0.0667 (8)0.0032 (5)0.0018 (6)0.0150 (6)
Cl20.0396 (7)0.0652 (9)0.0862 (10)0.0009 (6)0.0023 (6)0.0207 (8)
N10.040 (2)0.053 (3)0.065 (3)0.010 (2)0.003 (2)0.020 (2)
N20.049 (2)0.039 (2)0.074 (3)0.002 (2)0.011 (2)0.006 (2)
N30.044 (2)0.038 (2)0.090 (3)0.0026 (19)0.018 (2)0.007 (2)
N40.067 (7)0.060 (11)0.068 (6)0.008 (7)0.015 (5)0.001 (8)
N4'0.067 (7)0.060 (11)0.068 (6)0.008 (7)0.015 (5)0.001 (8)
O10.058 (2)0.0403 (19)0.076 (3)0.0096 (17)0.011 (2)0.0023 (18)
O20.086 (4)0.065 (3)0.077 (3)0.009 (3)0.027 (3)0.008 (3)
O2'0.078 (18)0.065 (18)0.072 (17)0.006 (14)0.016 (14)0.016 (15)
C10.035 (2)0.059 (3)0.057 (3)0.002 (2)0.005 (2)0.004 (2)
C20.036 (2)0.040 (3)0.058 (3)0.001 (2)0.005 (2)0.002 (2)
C30.040 (3)0.049 (3)0.047 (3)0.009 (2)0.004 (2)0.000 (2)
C40.049 (3)0.046 (3)0.068 (3)0.004 (2)0.000 (3)0.002 (3)
C50.036 (2)0.041 (3)0.056 (3)0.004 (2)0.001 (2)0.004 (2)
C60.070 (4)0.065 (4)0.093 (5)0.016 (3)0.007 (4)0.014 (3)
C70.094 (6)0.090 (6)0.082 (5)0.004 (5)0.034 (5)0.001 (5)
C80.177 (14)0.139 (10)0.110 (9)0.045 (9)0.059 (9)0.010 (8)
C7'0.094 (6)0.090 (6)0.082 (5)0.004 (5)0.034 (5)0.001 (5)
C8'0.14 (5)0.13 (5)0.10 (4)0.01 (4)0.02 (4)0.03 (4)
Geometric parameters (Å, º) top
N1—C11.470 (7)C2—C31.509 (7)
N1—C41.473 (7)C2—H2A0.9800
N1—H1A0.9000C3—C41.493 (7)
N1—H1B0.9000C4—H4A0.9700
N2—C51.297 (6)C4—H4B0.9700
N2—O11.393 (5)C6—H6A0.9600
N2—H20.8600C6—H6B0.9600
N3—C51.296 (6)C6—H6C0.9600
N3—H3A0.8600C7—C81.504 (14)
N3—H3B0.8600C7—H7A0.9700
N4—C31.26 (3)C7—H7B0.9700
N4—O21.40 (2)C8—H8A0.9600
N4'—C31.26 (16)C8—H8B0.9600
N4'—O2'1.39 (12)C8—H8C0.9600
O1—C61.423 (8)C7'—C8'1.53 (8)
O2—C71.454 (9)C7'—H7'10.9700
O2'—C7'1.45 (5)C7'—H7'20.9700
C1—C21.521 (7)C8'—H8'10.9600
C1—H1C0.9700C8'—H8'20.9600
C1—H1D0.9700C8'—H8'30.9600
C2—C51.507 (7)
C1—N1—C4106.7 (4)N1—C4—H4B111.2
C1—N1—H1A110.4C3—C4—H4B111.2
C4—N1—H1A110.4H4A—C4—H4B109.1
C1—N1—H1B110.4N3—C5—N2122.5 (5)
C4—N1—H1B110.4N3—C5—C2121.2 (4)
H1A—N1—H1B108.6N2—C5—C2116.3 (4)
C5—N2—O1118.1 (4)O1—C6—H6A109.5
C5—N2—H2120.9O1—C6—H6B109.5
O1—N2—H2120.9H6A—C6—H6B109.5
C5—N3—H3A120.0O1—C6—H6C109.5
C5—N3—H3B120.0H6A—C6—H6C109.5
H3A—N3—H3B120.0H6B—C6—H6C109.5
C3—N4—O2109.2 (14)O2—C7—C8105.9 (8)
C3—N4'—O2'109 (9)O2—C7—H7A110.6
N2—O1—C6109.5 (4)C8—C7—H7A110.6
N4—O2—C7108.0 (11)O2—C7—H7B110.6
N4'—O2'—C7'109 (7)C8—C7—H7B110.6
N1—C1—C2103.8 (4)H7A—C7—H7B108.7
N1—C1—H1C111.0C7—C8—H8A109.5
C2—C1—H1C111.0C7—C8—H8B109.5
N1—C1—H1D111.0H8A—C8—H8B109.5
C2—C1—H1D111.0C7—C8—H8C109.5
H1C—C1—H1D109.0H8A—C8—H8C109.5
C5—C2—C3113.7 (4)H8B—C8—H8C109.5
C5—C2—C1114.6 (4)O2'—C7'—C8'104 (4)
C3—C2—C1101.9 (4)O2'—C7'—H7'1110.9
C5—C2—H2A108.8C8'—C7'—H7'1110.9
C3—C2—H2A108.8O2'—C7'—H7'2110.9
C1—C2—H2A108.8C8'—C7'—H7'2110.9
N4—C3—C4128.4 (10)H7'1—C7'—H7'2108.9
N4'—C3—C4116 (6)C7'—C8'—H8'1109.5
N4—C3—C2121.6 (10)C7'—C8'—H8'2109.5
N4'—C3—C2133 (7)H8'1—C8'—H8'2109.5
C4—C3—C2110.0 (4)C7'—C8'—H8'3109.5
N1—C4—C3103.0 (4)H8'1—C8'—H8'3109.5
N1—C4—H4A111.2H8'2—C8'—H8'3109.5
C3—C4—H4A111.2
C5—N2—O1—C6104.6 (6)C5—C2—C3—C4137.4 (4)
C3—N4—O2—C7171.4 (14)C1—C2—C3—C413.5 (5)
C3—N4'—O2'—C7'167 (9)C1—N1—C4—C330.2 (5)
C4—N1—C1—C239.6 (5)N4—C3—C4—N1171.6 (16)
N1—C1—C2—C5154.7 (4)N4'—C3—C4—N1179 (8)
N1—C1—C2—C331.5 (5)C2—C3—C4—N19.5 (5)
O2—N4—C3—C41 (3)O1—N2—C5—N32.4 (8)
O2—N4—C3—C2177.3 (9)O1—N2—C5—C2177.8 (4)
O2'—N4'—C3—N413 (25)C3—C2—C5—N360.0 (6)
O2'—N4'—C3—C4163 (7)C1—C2—C5—N356.7 (6)
O2'—N4'—C3—C231 (17)C3—C2—C5—N2119.7 (5)
C5—C2—C3—N441.6 (15)C1—C2—C5—N2123.6 (5)
C1—C2—C3—N4165.4 (14)N4—O2—C7—C8176.7 (14)
C5—C2—C3—N4'29 (9)N4'—O2'—C7'—C8'143 (8)
C1—C2—C3—N4'153 (9)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3B···Cl10.862.293.144 (4)173
N3—H3A···Cl1i0.862.413.213 (4)156
N2—H2···Cl2ii0.862.213.029 (4)160
N1—H1B···Cl20.902.183.035 (4)159
N1—H1A···Cl1iii0.902.203.076 (4)165
Symmetry codes: (i) x+3/2, y+1/2, z; (ii) x+1/2, y+1/2, z; (iii) x+1, y, z+1.

Experimental details

Crystal data
Chemical formulaC8H18N4O22+·2Cl
Mr273.16
Crystal system, space groupOrthorhombic, Pbcn
Temperature (K)298
a, b, c (Å)12.7355 (14), 8.8506 (12), 26.334 (2)
V3)2968.3 (6)
Z8
Radiation typeMo Kα
µ (mm1)0.43
Crystal size (mm)0.23 × 0.20 × 0.19
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.907, 0.922
No. of measured, independent and
observed [I > 2σ(I)] reflections
14370, 2597, 1986
Rint0.062
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.077, 0.210, 1.08
No. of reflections2597
No. of parameters170
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.44, 0.33

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1999) and SHELXTL (Sheldrick, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3B···Cl10.862.293.144 (4)173.2
N3—H3A···Cl1i0.862.413.213 (4)156.2
N2—H2···Cl2ii0.862.213.029 (4)159.8
N1—H1B···Cl20.902.183.035 (4)158.7
N1—H1A···Cl1iii0.902.203.076 (4)164.7
Symmetry codes: (i) x+3/2, y+1/2, z; (ii) x+1/2, y+1/2, z; (iii) x+1, y, z+1.
 

Acknowledgements

This work was supported by the IMB Research Foundation.

References

First citationAnderson, V. E. & Osheroff, N. (2001). Curr. Pharm. Des. 7, 337–353.  Web of Science CrossRef PubMed CAS
First citationBall, P., Tilloston, G. & Fernald, A. (1998). Expert Opin. Investig. Drugs, 7, 761–783.  CrossRef PubMed CAS
First citationBruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationBruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationChoi, D. R., Shin, J. H. & Yang, J. (2004). Bioorg. Med. Chem. Lett. 14, 1273–1277.  Web of Science CrossRef PubMed CAS
First citationRay, S., Pathak, S. R. & Chaturvedi, D. (2005). Drugs Future, 30, 161–180.  Web of Science CrossRef CAS
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals
First citationWang, X. Y., Guo, Q. & Wang, Y. C. (2008). Acta Pharmacol. Sin. 43, 819–827.  CAS
First citationWang, J., Liu, M., Cao, J. & Wang, Y. (2008). Acta Cryst. E64, o2294.  Web of Science CSD CrossRef IUCr Journals

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