N-(7-Eth­oxy-1H-indazol-4-yl)-4-methyl­benzene­sulfonamide

Abbassi, N.; Rakib, E.M.; Zouihri, H.

doi:10.1107/S1600536811016576

organic compounds

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ISSN: 2056-9890

Volume 67| Part 6| June 2011| Page o1354

doi:10.1107/S1600536811016576

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N-(7-Ethoxy-1H-indazol-4-yl)-4-methylbenzenesulfonamide

Najat Abbassi,^a El Mostapha Rakib ^a ^* and Hafid Zouihri ^b

^aLaboratoire de Chimie Organique et Analytique, Université Sultan Moulay Slimane, Faculté des Sciences et Techniques, Béni-Mellal, BP 523, Morocco, and ^bLaboratoires de Diffraction des Rayons X, Centre Nationale pour la Recherche Scientifique et Technique, Rabat, Morocco
^*Correspondence e-mail: elmostapha1@ymail.com

(Received 25 April 2011; accepted 2 May 2011; online 7 May 2011)

The molecule of the title heterocyclic compound, C₁₆H₁₇N₃O₃S, is bent at the S atom with an C—SO₂—NH—C torsion angle of 80.17 (8)°. The phenyl substituent at the S atom is rotated out of the plane of the 1H-indazole ring [interplanar angle = 46.24 (8)°]. In the crystal, intermolecular N—H⋯N and N—H⋯O hydrogen bonds build up a ribbon developing parallel to the b-axis direction. C—H⋯O hydrogen bonds link these ribbons, forming a layer parallel to the bc plane.

Related literature

For related structures, see: Shakuntala et al. (2011a ,b ); Khan et al. (2010 ); Gowda et al. (2010 ). For the biological activity of similar sulfonamides, see: Soledade et al. (2006 ); Lee & Lee, (2002 ).

Experimental

Crystal data

C₁₆H₁₇N₃O₃S
M_r = 331.39
Monoclinic, P 2₁ /c
a = 16.2579 (4) Å
b = 5.0291 (1) Å
c = 20.4551 (5) Å
β = 97.269 (1)°
V = 1659.02 (7) Å³
Z = 4
Mo Kα radiation
μ = 0.21 mm⁻¹
T = 296 K
0.23 × 0.20 × 0.14 mm

Data collection

Bruker APEXII CCD detector diffractometer
31243 measured reflections
6745 independent reflections
5062 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.053
wR(F²) = 0.158
S = 1.07
6745 reflections
210 parameters
H-atom parameters constrained
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C14—H14B⋯O1ⁱ	0.97	2.54	3.373 (3)	144
N1—H14⋯O2ⁱⁱ	0.85	2.07	2.9159 (15)	172
N2—H2A⋯N3ⁱⁱⁱ	0.86	2.21	2.8974 (15)	136
Symmetry codes: (i) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (ii) x, y-1, z; (iii) -x+1, -y+3, -z+1.

Data collection: APEX2 (Bruker, 2005 ); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811016576/dn2681sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811016576/dn2681Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811016576/dn2681Isup3.mol

Supporting information file. DOI: 10.1107/S1600536811016576/dn2681Isup4.cml

checkCIF report

Comment top

Similar sulfonamides have been studied in various previously works [Shakuntala et al. 2011a and 2011b; Khan et al. 2010; Gowda et al. 2010] and have proved important functionalities for biological and anti-hypertensive activities [Soledade et al., 2006; Lee & Lee, 2002].

In the title compound, C₁₆H₁₇N₃O₃S, the molecule is bent at the S atom with an C—SO₂—NH—C torsion angle of 80.17 (8)° (Fig. 1). In the crystal structure, intermolecular N—H···N and N—H···O hydrogen bonds build up a ribbon developping parallel to the b direction and the C—H···O link these reibons to form a two D layer parallel to the bc plane (Fig. 2, Table 1).

The S atom has a distorted tetrahedral geometry [maximum deviation: O—S—O = 119.87 (9)°]. The phenyl substituent at S1 atom is rotated out of the plane of the 1H-indazol ring (the interplanar angles is 46.24 (8)°).

Related literature top

For related structures, see: Shakuntala et al. (2011a,b); Khan et al. (2010); Gowda et al. (2010). For the biological activity of similar sulfonamides, see: Soledade et al. (2006); Lee & Lee, (2002).

Experimental top

A mixture of 4-nitroindazole (1.22 mmol) and anhydrous SnCl₂ (1.1 g, 6.1 mmol) in 25 mL of absolute ethanol was heated at 60 °C for 2 h. After reduction, the starting material disappeared, and the solution was allowed to cool down. The pH was made slightly basic (pH 7–8) by addition of 5% aqueous potassium bicarbonate before extraction with ethyl acetate. The organic phase was washed with brine and dried over magnesium sulfate. The solvent was removed to afford the amine, which was immediately dissolved in pyridine (5 ml) and then reacted with 4-methylbenzenesulfonyl chloride (0.26 g, 1.25 mmol) at room temperature for 24 h. After the reaction mixture was concentrated in vacuo, the resulting residue was purified by flash chromatography (eluted with Ethyl acetate: Hexane 1:9).

Yield: 45%; mp: 443–445 °K; IR (KBr, cm^-1): 3340, 3235 (NH), 1595 (CN), 1335, 1160 (SO₂); ¹H NMR (DMSO-d₆): 2.27 (s, 3H, CH3), 6.92 (dd, 1H, J=2.1 Hz and 6.1 Hz), 7.16 (d, 2H, J=6.2 Hz), 7.28 (d, 2H, J=8.3 Hz), 7.68 (d, 2H, J=8.3 Hz), 8.22 (s, 1H),10.51 (s, 1H, NH), 13.05 (s, 1H, NH); ¹³C NMR (DMSO-d₆): 21.3 (CH3), 106.7,111.0, 126.9, 127.2, 130.1, 132.4 (6 CH), 117.3, 130.5, 137.3, 141.4, 143.7 (5 C); MS m/z=288 [M+1].

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Molecular view of the title compound showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii.
	Fig. 2. Partial packing view showing the chain formed by C—H···O, N—H···O and N—H···N hydrogen bondings. H atoms not involved in hydrogen bonds have been omitted for clarity.

N-(7-Ethoxy-1H-indazol-4-yl)-4-methylbenzenesulfonamide top

Crystal data top

C₁₆H₁₇N₃O₃S	F(000) = 696
M_r = 331.39	D_x = 1.327 Mg m⁻³
Monoclinic, P2₁/c	Melting point: 445 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 16.2579 (4) Å	Cell parameters from 347 reflections
b = 5.0291 (1) Å	θ = 2.7–27.2°
c = 20.4551 (5) Å	µ = 0.21 mm⁻¹
β = 97.269 (1)°	T = 296 K
V = 1659.02 (7) Å³	Prism, yellow
Z = 4	0.23 × 0.20 × 0.14 mm

Data collection top

Bruker APEXII CCD detector diffractometer	5062 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.025
Graphite monochromator	θ_max = 34.0°, θ_min = 1.3°
ω and ϕ scans	h = −25→25
31243 measured reflections	k = −7→7
6745 independent reflections	l = −32→31

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)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.158	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.0799P)² + 0.3561P] where P = (F_o² + 2F_c²)/3
6745 reflections	(Δ/σ)_max = 0.011
210 parameters	Δρ_max = 0.42 e Å⁻³
0 restraints	Δρ_min = −0.25 e Å⁻³

Crystal data top

C₁₆H₁₇N₃O₃S	V = 1659.02 (7) Å³
M_r = 331.39	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 16.2579 (4) Å	µ = 0.21 mm⁻¹
b = 5.0291 (1) Å	T = 296 K
c = 20.4551 (5) Å	0.23 × 0.20 × 0.14 mm
β = 97.269 (1)°

Data collection top

Bruker APEXII CCD detector diffractometer	5062 reflections with I > 2σ(I)
31243 measured reflections	R_int = 0.025
6745 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.053	0 restraints
wR(F²) = 0.158	H-atom parameters constrained
S = 1.07	Δρ_max = 0.42 e Å⁻³
6745 reflections	Δρ_min = −0.25 e Å⁻³
210 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
S1	0.202461 (19)	0.91282 (6)	0.304901 (17)	0.03746 (10)
N1	0.27119 (7)	0.7334 (2)	0.35009 (6)	0.0391 (2)
H14	0.2635	0.5696	0.3412	0.047*
N2	0.43721 (7)	1.2628 (2)	0.50079 (6)	0.0384 (2)
H2A	0.4616	1.3343	0.5362	0.046*
N3	0.45193 (7)	1.3298 (3)	0.43916 (6)	0.0416 (3)
O1	0.19501 (7)	0.8007 (3)	0.24030 (5)	0.0519 (3)
O2	0.22674 (7)	1.1855 (2)	0.31483 (6)	0.0524 (3)
O3	0.37858 (8)	1.0205 (3)	0.61280 (6)	0.0578 (3)
C1	0.08572 (13)	1.0406 (4)	0.38431 (11)	0.0631 (5)
H1	0.1221	1.1725	0.4018	0.076*
C2	0.00971 (15)	1.0085 (5)	0.40702 (13)	0.0794 (7)
H2	−0.0048	1.1212	0.4398	0.095*
C3	−0.04508 (12)	0.8132 (5)	0.38215 (12)	0.0712 (6)
C4	−0.02207 (11)	0.6462 (5)	0.33422 (11)	0.0651 (5)
H4	−0.0581	0.5121	0.3174	0.078*
C5	0.05334 (10)	0.6742 (4)	0.31072 (9)	0.0515 (4)
H5	0.0681	0.5593	0.2785	0.062*
C6	0.10683 (8)	0.8748 (3)	0.33547 (7)	0.0385 (3)
C7	0.29527 (7)	0.8035 (2)	0.41776 (7)	0.0346 (2)
C8	0.26575 (9)	0.6722 (3)	0.46859 (8)	0.0451 (3)
H8	0.2269	0.5376	0.4590	0.054*
C9	0.29232 (10)	0.7346 (3)	0.53502 (8)	0.0501 (4)
H9	0.2716	0.6385	0.5682	0.060*
C10	0.34852 (9)	0.9356 (3)	0.55166 (7)	0.0415 (3)
C11	0.37907 (7)	1.0689 (2)	0.49948 (6)	0.0338 (2)
C12	0.35467 (7)	1.0062 (2)	0.43349 (6)	0.0323 (2)
C13	0.40308 (8)	1.1763 (3)	0.39843 (7)	0.0381 (3)
H13	0.4008	1.1797	0.3528	0.046*
C14	0.36325 (16)	0.8578 (6)	0.66736 (10)	0.0814 (7)
H14A	0.3858	0.6811	0.6630	0.098*
H14B	0.3041	0.8422	0.6691	0.098*
C15	0.4038 (2)	0.9868 (8)	0.72770 (11)	0.1024 (9)
H15A	0.4610	1.0202	0.7232	0.154*
H15B	0.4005	0.8722	0.7648	0.154*
H15C	0.3765	1.1520	0.7344	0.154*
C16	−0.12866 (17)	0.7785 (10)	0.40632 (19)	0.1314 (14)
H16A	−0.1231	0.6624	0.4439	0.197*
H16B	−0.1671	0.7026	0.3718	0.197*
H16C	−0.1489	0.9484	0.4186	0.197*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.03566 (15)	0.03045 (15)	0.04463 (19)	−0.00315 (11)	−0.00135 (12)	−0.00309 (12)
N1	0.0377 (5)	0.0267 (4)	0.0501 (6)	−0.0007 (4)	−0.0058 (4)	−0.0085 (4)
N2	0.0355 (5)	0.0403 (5)	0.0385 (5)	−0.0137 (4)	0.0015 (4)	−0.0025 (4)
N3	0.0373 (5)	0.0444 (6)	0.0427 (6)	−0.0155 (5)	0.0038 (4)	0.0018 (5)
O1	0.0506 (6)	0.0608 (7)	0.0429 (6)	−0.0006 (5)	0.0011 (4)	−0.0066 (5)
O2	0.0501 (6)	0.0289 (5)	0.0755 (8)	−0.0068 (4)	−0.0021 (5)	0.0035 (5)
O3	0.0651 (7)	0.0711 (8)	0.0380 (5)	−0.0210 (6)	0.0100 (5)	−0.0019 (5)
C1	0.0635 (10)	0.0507 (9)	0.0779 (13)	−0.0091 (8)	0.0196 (9)	−0.0217 (9)
C2	0.0760 (14)	0.0735 (13)	0.0963 (17)	−0.0007 (12)	0.0407 (13)	−0.0193 (13)
C3	0.0481 (9)	0.0836 (14)	0.0844 (14)	−0.0007 (9)	0.0185 (9)	0.0131 (12)
C4	0.0438 (8)	0.0742 (12)	0.0748 (12)	−0.0200 (8)	−0.0020 (8)	0.0052 (10)
C5	0.0452 (7)	0.0516 (8)	0.0561 (9)	−0.0130 (6)	−0.0006 (6)	−0.0089 (7)
C6	0.0352 (5)	0.0330 (6)	0.0457 (7)	−0.0009 (4)	−0.0012 (5)	−0.0021 (5)
C7	0.0296 (5)	0.0273 (5)	0.0457 (7)	−0.0034 (4)	−0.0001 (4)	−0.0027 (5)
C8	0.0384 (6)	0.0372 (6)	0.0587 (9)	−0.0146 (5)	0.0027 (6)	0.0028 (6)
C9	0.0454 (7)	0.0533 (8)	0.0528 (8)	−0.0178 (6)	0.0110 (6)	0.0081 (7)
C10	0.0382 (6)	0.0464 (7)	0.0404 (6)	−0.0082 (5)	0.0076 (5)	0.0017 (5)
C11	0.0288 (5)	0.0326 (5)	0.0400 (6)	−0.0053 (4)	0.0041 (4)	−0.0007 (5)
C12	0.0278 (4)	0.0299 (5)	0.0387 (6)	−0.0046 (4)	0.0019 (4)	−0.0013 (4)
C13	0.0360 (5)	0.0406 (6)	0.0375 (6)	−0.0094 (5)	0.0040 (4)	0.0004 (5)
C14	0.0892 (15)	0.1092 (19)	0.0474 (10)	−0.0299 (14)	0.0152 (10)	0.0098 (11)
C15	0.118 (2)	0.146 (3)	0.0443 (11)	−0.024 (2)	0.0118 (12)	−0.0018 (14)
C16	0.0683 (16)	0.171 (4)	0.165 (3)	−0.012 (2)	0.058 (2)	0.001 (3)

Geometric parameters (Å, º) top

S1—O1	1.4277 (11)	C5—C6	1.3854 (19)
S1—O2	1.4345 (11)	C5—H5	0.9300
S1—N1	1.6296 (11)	C7—C8	1.369 (2)
S1—C6	1.7581 (14)	C7—C12	1.4133 (16)
N1—C7	1.4340 (17)	C8—C9	1.408 (2)
N1—H14	0.8492	C8—H8	0.9300
N2—N3	1.3550 (16)	C9—C10	1.376 (2)
N2—C11	1.3561 (15)	C9—H9	0.9300
N2—H2A	0.8600	C10—C11	1.4032 (18)
N3—C13	1.3241 (17)	C11—C12	1.3939 (17)
O3—C10	1.3529 (18)	C12—C13	1.4170 (17)
O3—C14	1.431 (2)	C13—H13	0.9300
C1—C6	1.378 (2)	C14—C15	1.474 (3)
C1—C2	1.384 (3)	C14—H14A	0.9700
C1—H1	0.9300	C14—H14B	0.9700
C2—C3	1.379 (3)	C15—H15A	0.9600
C2—H2	0.9300	C15—H15B	0.9600
C3—C4	1.378 (3)	C15—H15C	0.9600
C3—C16	1.514 (3)	C16—H16A	0.9600
C4—C5	1.379 (2)	C16—H16B	0.9600
C4—H4	0.9300	C16—H16C	0.9600

O1—S1—O2	119.88 (8)	C7—C8—H8	118.9
O1—S1—N1	106.15 (7)	C9—C8—H8	118.9
O2—S1—N1	107.00 (6)	C10—C9—C8	121.01 (13)
O1—S1—C6	108.12 (7)	C10—C9—H9	119.5
O2—S1—C6	107.07 (7)	C8—C9—H9	119.5
N1—S1—C6	108.17 (7)	O3—C10—C9	127.66 (14)
C7—N1—S1	119.69 (9)	O3—C10—C11	115.56 (12)
C7—N1—H14	117.4	C9—C10—C11	116.78 (13)
S1—N1—H14	110.1	N2—C11—C12	107.09 (11)
N3—N2—C11	111.41 (10)	N2—C11—C10	129.89 (12)
N3—N2—H2A	124.3	C12—C11—C10	122.95 (11)
C11—N2—H2A	124.3	C11—C12—C7	119.09 (11)
C13—N3—N2	106.15 (10)	C11—C12—C13	104.21 (10)
C10—O3—C14	117.55 (15)	C7—C12—C13	136.68 (12)
C6—C1—C2	119.19 (18)	N3—C13—C12	111.14 (12)
C6—C1—H1	120.4	N3—C13—H13	124.4
C2—C1—H1	120.4	C12—C13—H13	124.4
C3—C2—C1	121.5 (2)	O3—C14—C15	107.3 (2)
C3—C2—H2	119.3	O3—C14—H14A	110.3
C1—C2—H2	119.3	C15—C14—H14A	110.3
C4—C3—C2	118.40 (17)	O3—C14—H14B	110.3
C4—C3—C16	119.9 (2)	C15—C14—H14B	110.3
C2—C3—C16	121.7 (3)	H14A—C14—H14B	108.5
C3—C4—C5	121.26 (18)	C14—C15—H15A	109.5
C3—C4—H4	119.4	C14—C15—H15B	109.5
C5—C4—H4	119.4	H15A—C15—H15B	109.5
C4—C5—C6	119.43 (17)	C14—C15—H15C	109.5
C4—C5—H5	120.3	H15A—C15—H15C	109.5
C6—C5—H5	120.3	H15B—C15—H15C	109.5
C1—C6—C5	120.23 (15)	C3—C16—H16A	109.5
C1—C6—S1	120.31 (12)	C3—C16—H16B	109.5
C5—C6—S1	119.45 (12)	H16A—C16—H16B	109.5
C8—C7—C12	118.04 (12)	C3—C16—H16C	109.5
C8—C7—N1	122.39 (11)	H16A—C16—H16C	109.5
C12—C7—N1	119.49 (11)	H16B—C16—H16C	109.5
C7—C8—C9	122.11 (12)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C14—H14B···O1ⁱ	0.97	2.54	3.373 (3)	144
N1—H14···O2ⁱⁱ	0.85	2.07	2.9159 (15)	172
N2—H2A···N3ⁱⁱⁱ	0.86	2.21	2.8974 (15)	136

Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, y−1, z; (iii) −x+1, −y+3, −z+1.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₇N₃O₃S
M_r	331.39
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	16.2579 (4), 5.0291 (1), 20.4551 (5)
β (°)	97.269 (1)
V (Å³)	1659.02 (7)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.21
Crystal size (mm)	0.23 × 0.20 × 0.14

Data collection
Diffractometer	Bruker APEXII CCD detector diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	31243, 6745, 5062
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.787

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.053, 0.158, 1.07
No. of reflections	6745
No. of parameters	210
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.42, −0.25

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C14—H14B···O1ⁱ	0.97	2.54	3.373 (3)	144
N1—H14···O2ⁱⁱ	0.85	2.07	2.9159 (15)	172
N2—H2A···N3ⁱⁱⁱ	0.86	2.21	2.8974 (15)	136

Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, y−1, z; (iii) −x+1, −y+3, −z+1.

Acknowledgements

The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.

References

Bruker (2005). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Gowda, B. T., Foro, S., Nirmala, P. G. & Fuess, H. (2010). Acta Cryst. E66, o1702. Web of Science CSD CrossRef IUCr Journals Google Scholar
Khan, I. U., Ahmad, W., Arshad, M. N., Sharif, S. & Ahmed, J. (2010). Acta Cryst. E66, o2507. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lee, J. S. & Lee, C. H. (2002). Bull. Korean Chem. Soc. 23, 167–169. Web of Science CrossRef CAS Google Scholar
Shakuntala, K., Foro, S. & Gowda, B. T. (2011a). Acta Cryst. E67, o104. Web of Science CrossRef IUCr Journals Google Scholar
Shakuntala, K., Foro, S. & Gowda, B. T. (2011b). Acta Cryst. E67, o142. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Soledade, M., Pedras, C. & Jha, M. (2006). Bioorg. Med. Chem. 14, 4958–4979. Web of Science PubMed Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar