5-Acetyl-6-methyl-4-phenyl-1-(prop-2-yn­yl)-3,4-di­hydro­pyrimidin-2(1H)-one

Kaoukabi, H.; Taourirte, M.; Lazrek, H.B.; El Azhari, M.; Saadi, M.; El Ammari, L.

doi:10.1107/S2414314617018028

organic compounds

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ISSN: 2414-3146

Volume 2| Part 12| December 2017| x171802

https://doi.org/10.1107/S2414314617018028

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5-Acetyl-6-methyl-4-phenyl-1-(prop-2-ynyl)-3,4-dihydropyrimidin-2(1H)-one

Hanane Kaoukabi,^a,^b ^* Moha Taourirte,^a Hassan B. Lazrek,^b Mohamed El Azhari,^c Mohamed Saadi ^d and Lahcen El Ammari ^d

^aLaboratoire de Chimie Bio-organique et Macromoléculaire, Faculté des Sciences et Techniques Guéliz, Marrakech, Morocco, ^bLaboratoire de Chimie Biomoléculaire et Médicinale, Faculté des Sciences Semlalia, Marrakech, Morocco, ^cLaboratoire de la Matière Condensée et des Nanostructures, Faculté des Sciences et Techniques Guéliz, Marrakech, Morocco, and ^dLaboratoire de Chimie Appliquée des Matériaux, Centres des Sciences des Matériaux, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
^*Correspondence e-mail: h_kaoukabi@yahoo.com

Edited by C. Rizzoli, Universita degli Studi di Parma, Italy (Received 4 December 2017; accepted 18 December 2017; online 19 December 2017)

The 4-dihydropyrimidin-2(1H)-one moiety of the title molecule, C₁₆H₁₆N₂O₂, displays a half-chair conformation. The least-squares mean plane through this heterocycle is almost perpendicular to the aromatic ring [dihedral angle = 89.52 (8)°] and to the prop-2-ynyl chain [C—C—N—C torsion angle of −73.2 (2)°]. The mean plane through the acetyl group makes a dihedral angle of 30.93 (10)° with the mean plane of the heterocycle. There is an intramolecular C—H⋯O hydrogen bond forming an S(6) ring motif. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds forming inversion dimers.

Keywords: crystal structure; acetyl; phenyl; 4-dihydropyrimidin-2(1H)-one; propynyl; hydrogen bonds.

CCDC reference: 1812012

Structure description

In past decades, dihydropyrimidinones (DHPMs) and their derivatives have attracted considerable interest due to their heterocyclic scaffold and interesting pharmacological properties such as antiviral, antitumor, anti inflammatory as well their applications as calcium channel blockers and anticancer drugs (Ali et al., 2016 ; Desai et al., 2016 ; Xue et al., 2016 ; Dalil et al., 2016 ; Dhumaskar et al., 2014 ; Jetti et al., 2014 ). Different strategies have been used for the modification of 3,4-dihydropyrimidine-2(1H)-ones. For instance, N-alkylation is one of the most usable but other methods include mild base Cs₂CO₃, K₂CO₃ (Putatunda et al., 2012 ), the Mitsunobu-type reaction (Dallinger & Kappe, 2002 ), or phase-transfer catalysis (Singh et al., 2009 ). Unfortunately, these strategies suffer from the disadvantage that the procedures need to be carried out in harsh conditions. In this article, we present a convenient approach for the preparation of an N1-alkylated DHPM derivative as a major product using potassium t-butoxide in DMF at room temperature.

The molecule of the title compound is built up from a 3,4-dihydropyrimidin-2(1H)-one ring linked to an acetyl group, one prop-2-ynyl chain and to methyl and phenyl groups as shown in Fig. 1. The dihydropyrimidine ring adopts a half-chair conformation as indicated by the total puckering amplitude Q₂ = 0.3602 (15) Å, and spherical polar angle θ = 106.8 (2)° with φ2 = 10.5 (2)°. The dihedral angle between the mean plane passing through the heterocycle and that through the aromatic ring is 89.52 (8)°. The prop-2-ynyl chain is nearly perpendicular to the mean plane of the dihydropyrimidine ring, as indicated by the C9—C8—N1—C4 torsion angle of −73.2 (2)°. The molecular conformation is stabilized by an intramolecular C—H⋯O hydrogen bond (Table 1), forming an S(6) ring motif. In the crystal, molecules are linked together by pairs of N—H⋯O hydrogen bonds, forming inversion dimers (Fig. 2, Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7C⋯O1	0.96	2.21	2.862 (3)	125
N2—H2⋯O2ⁱ	0.86	2.02	2.8612 (17)	164
Symmetry code: (i) -x+1, -y+1, -z+1.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. The intramolecular hydrogen bond is shown as a dashed line.

Figure 2
Crystal packing of the title compound, showing molecules linked through N—H⋯O hydrogen bonds (dotted lines).

Synthesis and crystallization

The title compound was prepared in good yield (70%) through condensation of 5-acetyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (1 g, 4.34 mmol) with propargyl bromide (0.73 ml, 9.55 mmol) in the presence of potassium t-butoxide as a base in N,N-dimethylformamide (DMF, 10 ml) at room temperature for one h. After completion of the reaction (TLC), the product was extracted with ethyl acetate and washed with water (2 × 20 ml), the organic layer separated and dried over anhydrous sodium sulfate and the solvent was removed under reduced pressure. The resulting crude product was purified by a column packed with silica gel. The obtained product was crystallized by slow evaporation of n-hexane/ethyl acetate (7:3 v/v) mixture, m.p. 424 K.

The confirmation of the synthesized compound was performed by spectroscopic techniques. The compound showed signals in its ¹H NMR spectrum (DMSO-d₆) δ = 2.09 (s, 3H, CH3CO), 2.53 (s, 3H, CH3), 3.26 (s, 1H, CH), 4.39–4.62 (m, 2H, –CH₂–), 5.22 (s, 1H, H-4), 7.27–7.32 (m, 5H, CAr), 8.13 (s, 1H, N3—H). The ¹³C NMR (DMSO-d₆) spectrum signals appeared at: δ = 196.06 (CO), 151.92 (C-6), 147.32 (C-2), 142.99 (C-1′), 128.64 (C-4′), 128.64, 127.66 and 126.49 (other aromatic carbons), 113.23 (C-5), 80.31 (C-alkyne), 74.27 (CH-alkyne), 53.00 (C-4), 31.69 (–CH₂–), 30.30 (CH₃ at C-4′), 16.05 (CH₃ at C-6). Further, ESI–MS [M + H]⁺ mass spectrum showed the [M+1] ion peak at m/z 269.3, which is in agreement with the molecular formula C₁₆H₁₆N₂O₂. The IR spectrum of the compound showed an absorption band at 3301–3229 cm⁻¹ indicating the presence of Csp—H stretching. A strong absorption band at 3094 cm⁻¹ was attributed to the N–H stretching, and absorption bands at 2121, 1665, 1209 cm⁻¹ indicated the presence of C≡C, C=O and CN. UV/Vis (MeOH): λ_max = 300 and 222 nm.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Two outliers (200, 110) were omitted in the last cycles of refinement.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₆H₁₆N₂O₂
M_r	268.31
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	22.656 (2), 12.2607 (12), 10.2189 (10)
β (°)	100.363 (4)
V (Å³)	2792.3 (5)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.36 × 0.28 × 0.22

Data collection
Diffractometer	Bruker X8 APEX
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.645, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	38459, 3614, 2502
R_int	0.047
(sin θ/λ)_max (Å⁻¹)	0.676

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.046, 0.133, 1.02
No. of reflections	3614
No. of parameters	184
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.26, −0.23
Computer programs: APEX2 and SAINT (Bruker, 2009 ), SHELXT2014 (Sheldrick, 2015a ), SHELXL2014 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ), Mercury (Macrae et al., 2008 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1812012

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314617018028/rz4020sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617018028/rz4020Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314617018028/rz4020Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: Mercury (Macrae et al., 2008) and publCIF (Westrip, 2010).

5-Acetyl-6-methyl-4-phenyl-1-(prop-2-ynyl)-3,4-dihydropyrimidin-2(1H)-one top

Crystal data top

C₁₆H₁₆N₂O₂	D_x = 1.276 Mg m⁻³
M_r = 268.31	Melting point: 424 K
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 22.656 (2) Å	Cell parameters from 3614 reflections
b = 12.2607 (12) Å	θ = 2.7–28.7°
c = 10.2189 (10) Å	µ = 0.09 mm⁻¹
β = 100.363 (4)°	T = 296 K
V = 2792.3 (5) Å³	Prism, colourless
Z = 8	0.36 × 0.28 × 0.22 mm
F(000) = 1136

Data collection top

Bruker X8 APEX diffractometer	3614 independent reflections
Radiation source: fine-focus sealed tube	2502 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.047
φ and ω scans	θ_max = 28.7°, θ_min = 2.7°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −30→30
T_min = 0.645, T_max = 0.747	k = −16→16
38459 measured reflections	l = −13→11

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.046	w = 1/[σ²(F_o²) + (0.053P)² + 1.4276P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.133	(Δ/σ)_max < 0.001
S = 1.02	Δρ_max = 0.26 e Å⁻³
3614 reflections	Δρ_min = −0.23 e Å⁻³
184 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0026 (5)

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 H atoms were placed geometrically and isotropically refined with C–H = 0.93–0.98 Å, N–H = 0.86 Å, and with U_iso(H) = 1.2 U_eq(C, N) or 1.5 U_eq(C) for methyl H atoms. A rotating model was used for the methyl groups.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.37406 (10)	0.29201 (18)	0.92689 (19)	0.0762 (6)
H1A	0.3622	0.2494	0.9966	0.114*
H1B	0.3392	0.3247	0.8740	0.114*
H1C	0.4013	0.3482	0.9651	0.114*
C2	0.40429 (7)	0.21998 (14)	0.84101 (16)	0.0561 (4)
C3	0.41421 (6)	0.26245 (11)	0.71114 (14)	0.0431 (3)
C4	0.42533 (6)	0.19789 (12)	0.61119 (15)	0.0457 (3)
C5	0.45892 (6)	0.35303 (12)	0.49448 (16)	0.0479 (4)
C6	0.41194 (6)	0.38466 (11)	0.69024 (14)	0.0416 (3)
H6	0.4274	0.4189	0.7762	0.050*
C7	0.42452 (8)	0.07574 (13)	0.6116 (2)	0.0642 (5)
H7A	0.4647	0.0487	0.6187	0.096*
H7B	0.4005	0.0499	0.5304	0.096*
H7C	0.4078	0.0503	0.6859	0.096*
C8	0.43732 (9)	0.18379 (16)	0.37151 (19)	0.0668 (5)
H8A	0.4576	0.2249	0.3116	0.080*
H8B	0.4586	0.1154	0.3915	0.080*
C9	0.37589 (10)	0.16135 (14)	0.30636 (17)	0.0616 (5)
C10	0.32600 (12)	0.14343 (18)	0.2591 (2)	0.0814 (6)
H10	0.2863	0.1292	0.2215	0.098*
C11	0.34962 (6)	0.43142 (11)	0.64005 (14)	0.0416 (3)
C12	0.33358 (8)	0.52996 (13)	0.68949 (18)	0.0598 (4)
H12	0.3606	0.5657	0.7547	0.072*
C13	0.27831 (9)	0.57605 (15)	0.6439 (2)	0.0710 (5)
H13	0.2682	0.6419	0.6793	0.085*
C14	0.23830 (8)	0.52553 (16)	0.54682 (19)	0.0661 (5)
H14	0.2010	0.5569	0.5159	0.079*
C15	0.25341 (8)	0.42845 (17)	0.49538 (18)	0.0654 (5)
H15	0.2264	0.3942	0.4288	0.078*
C16	0.30871 (7)	0.38075 (14)	0.54179 (16)	0.0540 (4)
H16	0.3184	0.3144	0.5068	0.065*
N1	0.43908 (6)	0.24585 (10)	0.49518 (13)	0.0492 (3)
N2	0.45282 (5)	0.41268 (10)	0.60009 (13)	0.0475 (3)
H2	0.4741	0.4709	0.6161	0.057*
O1	0.42141 (8)	0.12989 (12)	0.88272 (15)	0.0905 (5)
O2	0.48212 (6)	0.38750 (10)	0.40209 (12)	0.0675 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0941 (14)	0.0835 (14)	0.0571 (11)	−0.0056 (11)	0.0301 (10)	0.0089 (10)
C2	0.0586 (9)	0.0570 (9)	0.0511 (9)	−0.0103 (7)	0.0057 (7)	0.0122 (7)
C3	0.0382 (7)	0.0428 (7)	0.0473 (8)	−0.0046 (5)	0.0048 (6)	0.0070 (6)
C4	0.0380 (7)	0.0426 (7)	0.0560 (9)	−0.0023 (6)	0.0071 (6)	0.0068 (6)
C5	0.0386 (7)	0.0504 (8)	0.0552 (9)	−0.0059 (6)	0.0101 (6)	0.0078 (7)
C6	0.0413 (7)	0.0419 (7)	0.0404 (7)	−0.0077 (5)	0.0039 (6)	0.0016 (6)
C7	0.0699 (11)	0.0420 (8)	0.0797 (12)	0.0004 (8)	0.0107 (9)	0.0044 (8)
C8	0.0777 (12)	0.0605 (10)	0.0713 (11)	−0.0010 (9)	0.0380 (10)	−0.0101 (9)
C9	0.0905 (14)	0.0508 (9)	0.0465 (9)	−0.0035 (9)	0.0206 (9)	−0.0069 (7)
C10	0.1027 (17)	0.0762 (14)	0.0599 (12)	−0.0077 (12)	0.0005 (11)	−0.0086 (10)
C11	0.0432 (7)	0.0411 (7)	0.0405 (7)	−0.0043 (6)	0.0077 (6)	0.0031 (6)
C12	0.0630 (10)	0.0492 (9)	0.0643 (10)	−0.0009 (7)	0.0040 (8)	−0.0085 (8)
C13	0.0704 (12)	0.0539 (10)	0.0884 (14)	0.0140 (9)	0.0133 (10)	−0.0021 (10)
C14	0.0553 (10)	0.0698 (12)	0.0730 (12)	0.0148 (8)	0.0107 (9)	0.0146 (9)
C15	0.0486 (9)	0.0828 (13)	0.0600 (10)	0.0009 (8)	−0.0028 (8)	−0.0049 (9)
C16	0.0482 (8)	0.0573 (9)	0.0546 (9)	−0.0004 (7)	0.0039 (7)	−0.0107 (7)
N1	0.0504 (7)	0.0467 (7)	0.0537 (7)	−0.0039 (5)	0.0180 (6)	−0.0010 (6)
N2	0.0425 (6)	0.0443 (6)	0.0556 (8)	−0.0130 (5)	0.0087 (5)	0.0035 (6)
O1	0.1257 (13)	0.0719 (9)	0.0762 (9)	0.0121 (8)	0.0239 (9)	0.0339 (8)
O2	0.0714 (8)	0.0715 (8)	0.0659 (7)	−0.0185 (6)	0.0294 (6)	0.0075 (6)

Geometric parameters (Å, º) top

C1—C2	1.495 (3)	C8—C9	1.457 (3)
C1—H1A	0.9600	C8—N1	1.470 (2)
C1—H1B	0.9600	C8—H8A	0.9700
C1—H1C	0.9600	C8—H8B	0.9700
C2—O1	1.222 (2)	C9—C10	1.167 (3)
C2—C3	1.480 (2)	C10—H10	0.9300
C3—C4	1.351 (2)	C11—C12	1.383 (2)
C3—C6	1.5131 (19)	C11—C16	1.385 (2)
C4—N1	1.4075 (19)	C12—C13	1.377 (2)
C4—C7	1.498 (2)	C12—H12	0.9300
C5—O2	1.2349 (18)	C13—C14	1.366 (3)
C5—N2	1.331 (2)	C13—H13	0.9300
C5—N1	1.3892 (19)	C14—C15	1.369 (3)
C6—N2	1.4600 (17)	C14—H14	0.9300
C6—C11	1.5248 (19)	C15—C16	1.387 (2)
C6—H6	0.9800	C15—H15	0.9300
C7—H7A	0.9600	C16—H16	0.9300
C7—H7B	0.9600	N2—H2	0.8600
C7—H7C	0.9600

C2—C1—H1A	109.5	C9—C8—H8A	109.3
C2—C1—H1B	109.5	N1—C8—H8A	109.3
H1A—C1—H1B	109.5	C9—C8—H8B	109.3
C2—C1—H1C	109.5	N1—C8—H8B	109.3
H1A—C1—H1C	109.5	H8A—C8—H8B	108.0
H1B—C1—H1C	109.5	C10—C9—C8	177.27 (19)
O1—C2—C3	122.76 (17)	C9—C10—H10	180.0
O1—C2—C1	118.65 (16)	C12—C11—C16	118.11 (14)
C3—C2—C1	118.55 (15)	C12—C11—C6	119.59 (13)
C4—C3—C2	123.42 (14)	C16—C11—C6	122.25 (13)
C4—C3—C6	118.66 (13)	C13—C12—C11	121.18 (16)
C2—C3—C6	117.92 (13)	C13—C12—H12	119.4
C3—C4—N1	119.44 (13)	C11—C12—H12	119.4
C3—C4—C7	125.43 (14)	C14—C13—C12	120.28 (17)
N1—C4—C7	115.12 (14)	C14—C13—H13	119.9
O2—C5—N2	123.52 (14)	C12—C13—H13	119.9
O2—C5—N1	120.68 (15)	C13—C14—C15	119.60 (17)
N2—C5—N1	115.77 (13)	C13—C14—H14	120.2
N2—C6—C3	108.24 (11)	C15—C14—H14	120.2
N2—C6—C11	110.69 (11)	C14—C15—C16	120.55 (17)
C3—C6—C11	115.19 (11)	C14—C15—H15	119.7
N2—C6—H6	107.5	C16—C15—H15	119.7
C3—C6—H6	107.5	C11—C16—C15	120.29 (16)
C11—C6—H6	107.5	C11—C16—H16	119.9
C4—C7—H7A	109.5	C15—C16—H16	119.9
C4—C7—H7B	109.5	C5—N1—C4	121.35 (13)
H7A—C7—H7B	109.5	C5—N1—C8	116.37 (13)
C4—C7—H7C	109.5	C4—N1—C8	122.15 (13)
H7A—C7—H7C	109.5	C5—N2—C6	123.52 (12)
H7B—C7—H7C	109.5	C5—N2—H2	118.2
C9—C8—N1	111.51 (13)	C6—N2—H2	118.2

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7C···O1	0.96	2.21	2.862 (3)	125
N2—H2···O2ⁱ	0.86	2.02	2.8612 (17)	164

Symmetry code: (i) −x+1, −y+1, −z+1.

Acknowledgements

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

References

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