organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

Iso­propyl 4-amino­benzoate

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aDepartment of Chemistry, B. N. M. Institute of Technology, Bengaluru 560 070, India, bDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysuru 570 006, India, cT. John Institute of Technology, Begaluru 560 083, India, dInstitute of Materials Science, Darmstadt University of Technology, Petersenstrasse 23, D-64287 Darmstadt, Germany, and eDepartment of Chemistry, Howard University, 525 College Street NW, Washington DC 20059, USA
*Correspondence e-mail: yathirajan@hotmail.com

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 16 August 2022; accepted 10 September 2022; online 15 September 2022)

The title compound, C10H13NO2, crystallizes with two mol­ecules (A and B) in the asymmetric unit. For A, the dihedral angle between the plane of the phenyl ring and the i-propyl substituent is 65.4 (3)° while for B this angle is 67.8 (3)°. In the crystal, the mol­ecules are linked by N—H⋯O and N—H⋯N hydrogen bonds to generate double chains propagating in the [100] direction.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Isopropyl 4-amino­benzoate, C10H13NO2, serves as a model drug in correlation studies between HPLC retention parameters and percutaneous absorption (Fu & Liang, 1994[Fu, X. C. & Liang, W. Q. (1994). Yao Xue Xue Bao 29, 74-77.]). It functions as an inhibitor or an alternative acceptor substrate in the enzymatic acetyl­ation of p-nitro­aniline (Hanna et al., 1990[Hanna, P. E., El-ghandour, A. M. & McCormack, M. E. (1990). Xenobiotica, 20, 739-751.]). The related compound risocaine (propyl 4-amino­benzoate) is a local anesthetic (Imai et al., 2006[Imai, T., Taketani, M., Shii, M., Hosokawa, M. & Chiba, K. (2006). Drug Metab. Dispos. 34, 1734-1741.]), whereas benzocaine (ethyl 4-amino­benzoate) is utilized as a topical pain reliever (Fischer & Ganellin, 2006[Fischer, J. & Ganellin, C. R. (2006). Analogue-based Drug Discovery, p. 475. Chichester: John Wiley & Sons.]).

Some related crystal structures viz., the monoclinic form of ethyl 4-amino­benzoate (Lynch & McClenaghan, 2002[Lynch, D. E. & McClenaghan, I. (2002). Acta Cryst. E58, o708-o709.]), form (II) of benzocaine (Chan et al., 2009[Chan, E. J., Rae, A. D. & Welberry, T. R. (2009). Acta Cryst. B65, 509-515.]; Chan & Welberry, 2010[Chan, E. J. & Welberry, T. R. (2010). Acta Cryst. B66, 260-270.]), 4-methyl­benzyl 4-amino­benzoate (Haider et al., 2010[Haider, A., Akhter, Z., Khan, M., Bolte, M. & Siddiqi, H. M. (2010). Acta Cryst. E66, o736.]), 2-(di­methyl­amino)­ethyl 4-amino­benzoate (Li et al., 2019[Li, L., Liu, H., Wu, Z., Miao, J. & Zhang, S. (2019). Z. Kristallogr. New Cryst. Struct. 234, 245-246.]) and a new high-pressure benzocaine polymorph (Patyk-Kaźmierczak & Kaźmierczak, 2020[Patyk-Kaźmierczak, E. & Kaźmierczak, M. (2020). Acta Cryst. B76, 56-64.]) have been reported.

The present paper reports the synthesis and crystal structure of the title compound, (I). Compound I crystallizes with two mol­ecules in the asymmetric unit (Fig. 1[link]). There are slight differences in the conformations of each mol­ecule: for A, the dihedral angle between the planes of the phenyl ring and its i-propyl substituent is 65.4 (3)° while for B this angle is 67.8 (3)°. For both mol­ecules, the H atoms of the amino substituents are not coplanar with their attached phenyl ring. This is indicated by the dihedral angles between this group and its phenyl ring [11.5 (3) and 24.2 (5)° for A and B, respectively] and the sum of the angles subtended at the N (358 and 352° for A and B, respectively), which shows that N2 is slightly more pyramidal than N1. These differences in the conformations of A and B are most clearly shown in an overlay of both mol­ecules centered on the phenyl ring of both (Fig. 2[link]).

[Figure 1]
Figure 1
The mol­ecular structure of I with displacement ellipsoids drawn at the 30% probability level.
[Figure 2]
Figure 2
An overlap of mol­ecules A and B centered on the phenyl rings of both mol­ecules showing the differences in both conformers involving the conformations of both the NH2 and i-propyl substituents.

In the extended structure of I, the mol­ecules are linked by N—H⋯O and N—H⋯N hydrogen bonds (Table 1[link]) to generate double chains propagating in the [100] direction (Fig. 2[link]). The chains consist of AAA and BBB mol­ecules linked by N1—H11N⋯O2 and N2—H21N⋯O4 hydrogen bonds, respectively, which both generate C(8) chains, with the N1—H12N⋯O2 and N2—H22N⋯O hydrogen bonds cross-linking the chains (Fig. 3[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H11N⋯O2i 0.87 (2) 2.23 (2) 3.060 (4) 158 (3)
N1—H12N⋯N2ii 0.88 (2) 2.39 (2) 3.269 (5) 176 (4)
N2—H21N⋯O4i 0.87 (2) 2.07 (2) 2.930 (4) 168 (4)
N2—H22N⋯O2i 0.87 (2) 2.36 (2) 3.224 (5) 172 (4)
Symmetry codes: (i) [x-1, y, z]; (ii) [-x, -y, -z+1].
[Figure 3]
Figure 3
Partial packing diagram for I showing the formation of [100] double chains linked by N—H⋯O and N—H⋯N hydrogen bonds (shown as dashed lines).

Synthesis and crystallization

4-Amino­benzoic acid (1.0 g), purchased from Sigma–Aldrich, was taken in a 100 ml round-bottomed flask. Then, 20 ml of 2-propanol and a catalytic amount of conc. H2SO4 was added and the reaction mixture was refluxed for 4 h. The reaction was confirmed to be complete using thin-layer chromatography and the mixture was then quenched with water, the precipitate formed was collected by filtration and dried. Pink needles suitable for single-crystal X-ray diffraction were grown by slow evaporation, at room temperature of a solution in ethyl acetate. Yield (79%), m. p. 355–357 K. The reaction scheme is shown in Fig. 4[link].

[Figure 4]
Figure 4
Reaction scheme.

Refinement

Crystal data, data collection and structure refinement details for I are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C10H13NO2
Mr 179.21
Crystal system, space group Triclinic, P[\overline{1}]
Temperature (K) 296
a, b, c (Å) 8.405 (1), 11.029 (2), 11.520 (3)
α, β, γ (°) 89.10 (2), 77.06 (2), 87.17 (2)
V3) 1039.5 (4)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.08
Crystal size (mm) 0.48 × 0.10 × 0.06
 
Data collection
Diffractometer Oxford Diffraction Xcalibur CCD
Absorption correction Multi-scan (CrysAlis RED; Oxford Diffraction, 2009[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Abingdon, England.])
Tmin, Tmax 0.461, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 6595, 3730, 1275
Rint 0.062
(sin θ/λ)max−1) 0.600
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.083, 0.135, 0.98
No. of reflections 3730
No. of parameters 251
No. of restraints 4
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.11, −0.14
Computer programs: CrysAlis CCD (Oxford Diffraction, 2009[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Abingdon, England.]), CrysAlis RED (Oxford Diffraction, 2009[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Abingdon, England.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014/6 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Structural data


Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2009); cell refinement: CrysAlis RED (Oxford Diffraction, 2009); data reduction: CrysAlis RED (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/6 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Isopropyl 4-aminobenzoate top
Crystal data top
C10H13NO2Z = 4
Mr = 179.21F(000) = 384
Triclinic, P1Dx = 1.145 Mg m3
a = 8.405 (1) ÅMo Kα radiation, λ = 0.71073 Å
b = 11.029 (2) ÅCell parameters from 837 reflections
c = 11.520 (3) Åθ = 2.6–28.0°
α = 89.10 (2)°µ = 0.08 mm1
β = 77.06 (2)°T = 296 K
γ = 87.17 (2)°Needle, pink
V = 1039.5 (4) Å30.48 × 0.10 × 0.06 mm
Data collection top
Oxford Diffraction Xcalibur CCD
diffractometer
1275 reflections with I > 2σ(I)
Radiation source: Enhance (Mo) X-ray SourceRint = 0.062
ω scansθmax = 25.3°, θmin = 2.6°
Absorption correction: multi-scan
(CrysalisRed; Oxford Diffraction, 2009)
h = 109
Tmin = 0.461, Tmax = 1.000k = 713
6595 measured reflectionsl = 1313
3730 independent reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.083Hydrogen site location: mixed
wR(F2) = 0.135H atoms treated by a mixture of independent and constrained refinement
S = 0.98 w = 1/[σ2(Fo2) + (0.0372P)2]
where P = (Fo2 + 2Fc2)/3
3730 reflections(Δ/σ)max < 0.001
251 parametersΔρmax = 0.11 e Å3
4 restraintsΔρmin = 0.14 e Å3
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. All hydrogen atoms were placed geometrically and refined as riding atoms with their Uiso values 1.2 times (1.5 times for CH3) that of their attached atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.8880 (3)0.1710 (2)0.0611 (2)0.0724 (8)
O20.9815 (3)0.0696 (2)0.2037 (2)0.0859 (10)
N10.2362 (5)0.0792 (3)0.3053 (3)0.0825 (11)
H11N0.160 (4)0.056 (3)0.268 (3)0.099*
H12N0.207 (4)0.116 (3)0.374 (2)0.099*
C10.7041 (4)0.0527 (3)0.1917 (3)0.0520 (10)
C20.6632 (5)0.0177 (3)0.2936 (4)0.0677 (12)
H20.7421140.0363940.3370170.081*
C30.5097 (5)0.0607 (3)0.3327 (3)0.0679 (12)
H30.4860520.1074750.4017600.082*
C40.3891 (5)0.0345 (3)0.2689 (4)0.0604 (11)
C50.4306 (5)0.0348 (3)0.1661 (4)0.0666 (11)
H50.3525920.0523650.1216390.080*
C60.5839 (5)0.0780 (3)0.1283 (3)0.0609 (11)
H60.6076610.1248700.0593230.073*
C70.8696 (5)0.0957 (3)0.1551 (4)0.0627 (11)
C81.0471 (5)0.2228 (4)0.0148 (4)0.0802 (13)
H81.1335900.1597150.0138900.096*
C91.0485 (5)0.2620 (4)0.1104 (4)0.1137 (16)
H9A1.1536380.2914400.1468850.171*
H9B0.9658870.3253950.1098770.171*
H9C1.0267440.1941070.1547640.171*
C101.0704 (5)0.3246 (4)0.0924 (4)0.1263 (18)
H10A1.1765830.3559140.0631780.190*
H10B1.0614860.2953630.1724140.190*
H10C0.9880980.3879000.0914510.190*
O30.3779 (3)0.4487 (2)0.6988 (3)0.0712 (8)
O40.5570 (3)0.3581 (2)0.5474 (2)0.0782 (9)
N20.1326 (5)0.2278 (4)0.4435 (3)0.0884 (12)
H21N0.223 (3)0.273 (3)0.465 (3)0.106*
H22N0.113 (5)0.185 (3)0.379 (2)0.106*
C110.2710 (5)0.3471 (3)0.5583 (4)0.0539 (10)
C120.2909 (5)0.2638 (4)0.4678 (4)0.0657 (11)
H120.3953050.2332010.4324960.079*
C130.1594 (5)0.2250 (3)0.4288 (4)0.0727 (13)
H130.1758300.1673940.3686590.087*
C140.0023 (6)0.2703 (4)0.4777 (4)0.0624 (11)
C150.0176 (5)0.3553 (4)0.5675 (3)0.0658 (12)
H150.1217990.3871770.6015760.079*
C160.1145 (5)0.3934 (3)0.6073 (3)0.0637 (11)
H160.0983480.4506950.6676880.076*
C170.4164 (6)0.3833 (3)0.5982 (4)0.0607 (12)
C180.5132 (5)0.4917 (4)0.7453 (4)0.0777 (13)
H180.6047970.5104350.6794010.093*
C190.5659 (5)0.3927 (4)0.8238 (4)0.1091 (16)
H19A0.6519560.4207710.8575620.164*
H19B0.6046010.3216710.7768740.164*
H19C0.4745750.3732540.8865690.164*
C200.4458 (5)0.6058 (4)0.8133 (4)0.1175 (17)
H20A0.5314150.6422470.8414490.176*
H20B0.3597700.5858740.8798230.176*
H20C0.4035480.6618030.7617390.176*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.062 (2)0.0778 (19)0.079 (2)0.0114 (15)0.0180 (16)0.0140 (16)
O20.063 (2)0.102 (2)0.100 (2)0.0073 (16)0.0353 (18)0.0239 (17)
N10.062 (3)0.079 (3)0.110 (3)0.014 (2)0.025 (3)0.015 (2)
C10.050 (3)0.047 (2)0.063 (3)0.001 (2)0.021 (2)0.002 (2)
C20.065 (3)0.070 (3)0.074 (3)0.004 (2)0.029 (3)0.012 (3)
C30.068 (3)0.063 (3)0.075 (3)0.003 (2)0.023 (3)0.014 (2)
C40.055 (3)0.046 (3)0.082 (3)0.001 (2)0.018 (3)0.007 (2)
C50.065 (3)0.068 (3)0.072 (3)0.001 (2)0.027 (3)0.001 (2)
C60.066 (3)0.059 (3)0.060 (3)0.004 (2)0.019 (3)0.004 (2)
C70.064 (3)0.060 (3)0.065 (3)0.003 (2)0.017 (3)0.001 (2)
C80.062 (3)0.083 (3)0.095 (4)0.011 (3)0.016 (3)0.019 (3)
C90.105 (4)0.140 (4)0.091 (4)0.021 (3)0.009 (3)0.040 (3)
C100.130 (5)0.132 (4)0.125 (4)0.066 (3)0.033 (4)0.004 (4)
O30.0559 (19)0.081 (2)0.078 (2)0.0044 (15)0.0158 (17)0.0163 (17)
O40.0491 (18)0.088 (2)0.092 (2)0.0018 (16)0.0030 (17)0.0148 (16)
N20.063 (3)0.112 (4)0.091 (3)0.005 (2)0.019 (3)0.032 (2)
C110.050 (3)0.055 (3)0.055 (3)0.001 (2)0.008 (2)0.001 (2)
C120.050 (3)0.075 (3)0.068 (3)0.007 (2)0.007 (2)0.003 (3)
C130.061 (3)0.080 (3)0.079 (3)0.008 (3)0.020 (3)0.020 (2)
C140.055 (3)0.068 (3)0.065 (3)0.004 (3)0.014 (3)0.001 (2)
C150.046 (3)0.078 (3)0.069 (3)0.007 (2)0.005 (2)0.009 (3)
C160.064 (3)0.060 (3)0.064 (3)0.003 (3)0.009 (3)0.006 (2)
C170.066 (3)0.048 (3)0.065 (3)0.001 (3)0.009 (3)0.006 (2)
C180.062 (3)0.084 (3)0.089 (3)0.010 (3)0.020 (3)0.013 (3)
C190.104 (4)0.125 (4)0.109 (4)0.001 (3)0.048 (3)0.003 (3)
C200.107 (4)0.108 (4)0.142 (5)0.005 (3)0.035 (3)0.052 (4)
Geometric parameters (Å, º) top
O1—C71.340 (4)O3—C171.343 (4)
O1—C81.465 (4)O3—C181.462 (4)
O2—C71.218 (4)O4—C171.216 (4)
N1—C41.373 (5)N2—C141.386 (5)
N1—H11N0.870 (18)N2—H21N0.873 (18)
N1—H12N0.876 (18)N2—H22N0.866 (18)
C1—C21.384 (4)C11—C121.377 (4)
C1—C61.389 (4)C11—C161.386 (4)
C1—C71.461 (5)C11—C171.472 (5)
C2—C31.373 (4)C12—C131.372 (4)
C2—H20.9300C12—H120.9300
C3—C41.396 (4)C13—C141.386 (5)
C3—H30.9300C13—H130.9300
C4—C51.386 (5)C14—C151.383 (4)
C5—C61.371 (4)C15—C161.378 (4)
C5—H50.9300C15—H150.9300
C6—H60.9300C16—H160.9300
C8—C101.493 (5)C18—C201.510 (4)
C8—C91.497 (5)C18—C191.518 (4)
C8—H80.9800C18—H180.9800
C9—H9A0.9600C19—H19A0.9600
C9—H9B0.9600C19—H19B0.9600
C9—H9C0.9600C19—H19C0.9600
C10—H10A0.9600C20—H20A0.9600
C10—H10B0.9600C20—H20B0.9600
C10—H10C0.9600C20—H20C0.9600
C7—O1—C8119.2 (3)C17—O3—C18117.3 (3)
C4—N1—H11N119 (3)C14—N2—H21N115 (3)
C4—N1—H12N121 (3)C14—N2—H22N116 (3)
H11N—N1—H12N118 (4)H21N—N2—H22N121 (4)
C2—C1—C6117.5 (4)C12—C11—C16118.2 (4)
C2—C1—C7119.4 (3)C12—C11—C17118.8 (4)
C6—C1—C7123.1 (4)C16—C11—C17123.1 (4)
C3—C2—C1122.1 (3)C13—C12—C11121.2 (4)
C3—C2—H2118.9C13—C12—H12119.4
C1—C2—H2118.9C11—C12—H12119.4
C2—C3—C4120.1 (4)C12—C13—C14121.0 (4)
C2—C3—H3119.9C12—C13—H13119.5
C4—C3—H3119.9C14—C13—H13119.5
N1—C4—C5121.4 (4)C15—C14—N2120.3 (4)
N1—C4—C3120.9 (4)C15—C14—C13117.9 (4)
C5—C4—C3117.8 (4)N2—C14—C13121.7 (4)
C6—C5—C4121.6 (4)C16—C15—C14121.1 (4)
C6—C5—H5119.2C16—C15—H15119.5
C4—C5—H5119.2C14—C15—H15119.5
C5—C6—C1120.9 (4)C15—C16—C11120.7 (4)
C5—C6—H6119.6C15—C16—H16119.7
C1—C6—H6119.6C11—C16—H16119.7
O2—C7—O1121.8 (4)O4—C17—O3122.4 (4)
O2—C7—C1125.3 (4)O4—C17—C11125.0 (4)
O1—C7—C1112.9 (4)O3—C17—C11112.6 (4)
O1—C8—C10110.1 (4)O3—C18—C20105.2 (3)
O1—C8—C9106.2 (3)O3—C18—C19108.4 (3)
C10—C8—C9113.1 (4)C20—C18—C19112.8 (4)
O1—C8—H8109.1O3—C18—H18110.1
C10—C8—H8109.1C20—C18—H18110.1
C9—C8—H8109.1C19—C18—H18110.1
C8—C9—H9A109.5C18—C19—H19A109.5
C8—C9—H9B109.5C18—C19—H19B109.5
H9A—C9—H9B109.5H19A—C19—H19B109.5
C8—C9—H9C109.5C18—C19—H19C109.5
H9A—C9—H9C109.5H19A—C19—H19C109.5
H9B—C9—H9C109.5H19B—C19—H19C109.5
C8—C10—H10A109.5C18—C20—H20A109.5
C8—C10—H10B109.5C18—C20—H20B109.5
H10A—C10—H10B109.5H20A—C20—H20B109.5
C8—C10—H10C109.5C18—C20—H20C109.5
H10A—C10—H10C109.5H20A—C20—H20C109.5
H10B—C10—H10C109.5H20B—C20—H20C109.5
C6—C1—C2—C30.6 (5)C16—C11—C12—C131.5 (5)
C7—C1—C2—C3179.9 (3)C17—C11—C12—C13178.7 (3)
C1—C2—C3—C40.3 (6)C11—C12—C13—C141.3 (5)
C2—C3—C4—N1178.5 (4)C12—C13—C14—C150.4 (5)
C2—C3—C4—C50.4 (5)C12—C13—C14—N2176.8 (4)
N1—C4—C5—C6178.9 (4)N2—C14—C15—C16176.3 (3)
C3—C4—C5—C60.9 (5)C13—C14—C15—C160.2 (5)
C4—C5—C6—C10.6 (6)C14—C15—C16—C110.1 (5)
C2—C1—C6—C50.1 (5)C12—C11—C16—C151.0 (5)
C7—C1—C6—C5179.6 (3)C17—C11—C16—C15179.3 (3)
C8—O1—C7—O20.4 (5)C18—O3—C17—O41.3 (5)
C8—O1—C7—C1179.3 (3)C18—O3—C17—C11178.8 (3)
C2—C1—C7—O24.2 (6)C12—C11—C17—O410.3 (5)
C6—C1—C7—O2175.2 (4)C16—C11—C17—O4169.4 (4)
C2—C1—C7—O1174.6 (3)C12—C11—C17—O3169.6 (3)
C6—C1—C7—O15.9 (5)C16—C11—C17—O310.6 (5)
C7—O1—C8—C1077.8 (4)C17—O3—C18—C20152.5 (3)
C7—O1—C8—C9159.5 (3)C17—O3—C18—C1986.6 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H11N···O2i0.87 (2)2.23 (2)3.060 (4)158 (3)
N1—H12N···N2ii0.88 (2)2.39 (2)3.269 (5)176 (4)
N2—H21N···O4i0.87 (2)2.07 (2)2.930 (4)168 (4)
N2—H22N···O2i0.87 (2)2.36 (2)3.224 (5)172 (4)
Symmetry codes: (i) x1, y, z; (ii) x, y, z+1.
 

Acknowledgements

PP is grateful to the B. N. M. Institute of Technology for research facilities and HSY thanks UGC for a BSR Faculty Fellowship for three years.

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