A dibenzo­furan derivative: 2-(pent­yloxy)dibenzo[b,d]furan

Goyal, N.; Donahue, J.P.; Do, C.; Perry, T.; Bongay-Williams, K.; Foroozesh, M.

doi:10.1107/S2414314618013068

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 3| Part 9| September 2018| x181306

https://doi.org/10.1107/S2414314618013068

Open

access

A dibenzofuran derivative: 2-(pentyloxy)dibenzo[b,d]furan

Navneet Goyal,^a ^* James P. Donahue,^b Camilla Do,^a Timothy Perry,^a Kyla Bongay-Williams ^a and Maryam Foroozesh ^a

^aDepartment of Chemistry, Xavier University of Louisiana, 1 Drexel Dr., New Orleans, Louisiana 70125, USA, and ^bDepartment of Chemistry, Tulane University, 6400 Freret Street, New Orleans, Louisiana 70118-5698, USA
^*Correspondence e-mail: ngoyal@xula.edu

Edited by I. Brito, University of Antofagasta, Chile (Received 23 August 2018; accepted 14 September 2018; online 28 September 2018)

The title compound, C₁₇H₁₈O₂, crystallizes in two-dimensional sheets, in which the 2-(pentyloxy)dibenzo[b,d]furan molecules are arranged in a head-to-head and tail-to-tail fashion that enables hydrophobic interactions between fully extended 2-pentoxy chains and π–π stacking between dibenzofuran rings in adjacent rings. Nearest intermolecular π-π stacking contacts are 3.3731 (12) Å. The molecule is nearly planar with an r.m.s. deviation of 0.0803 Å from the mean plane defined by the nineteen non-hydrogen atoms.

Keywords: crystal structure; dibenzofuran; π–π stacking interactions; hydrophobic interactions; P450 inhibitor.

CCDC reference: 1867924

Structure description

Natural products and their structurally diverse derivatives play a major role in drug discovery and development (Cragg et al., 1997 ). Derivatives of dibenzofuran, a three-ring fused system, have shown interesting biological activities as therapeutics for diseases such as cancer, thombosis, tuberculosis, etc (Yurtasş et al., 2016 ; Kantevari et al., 2011 ; Chiranjeevi et al., 2013 ). Our lab is studying the design and synthesis of new inhibitors of P450 enzymes, which are a superfamily of heme proteins involved in the metabolism and detoxification of endogenous and exogenous compounds (Sridhar et al., 2017 ). P450s are involved in the bioactivation of certain procarcinogens leading to the production of carcinogenic species. The development of potent and selective P450 enzyme inhibitors has attracted considerable attention over the years and has become an important cancer prevention target (Alexander et al., 1995 ; Foroozesh et al., 1997 ; Sridhar et al., 2017; Foroozesh et al., 2013 ).

Previous studies in our laboratory have shown that P450 1A1 accommodates linear polycyclic aromatic molecules while P450 1A2 prefers triangle-shaped molecules. [The 1A1 nomenclature designates enzymes belonging to family 1, subfamily A, polypeptide 1, as encoded by the CYP1A1 gene; the 1A2 notation is similarly defined.] These substrate preferences have led to the design of several triangle-shaped carbazole derivatives in an attempt to synthesize potentially selective inhibitors for P450 1A2 over P450 1A1. We are also interested in synthesizing molecules that have fused-ring systems such as dibenzofuran in our pursuit of active P450 inhibitors.

In the crystalline state, the 2-pentyloxy substituent in the title compound occurs in a fully extended, linear conformation in which it is nearly coplanar with the dibenzofuran ring system (Fig. 1). The r.m.s. deviation from the mean plane defined by the nineteen non-hydrogen atoms is 0.0803 Å, with the largest departure being seen for O2 at 0.178 (2) Å. The distinctive feature of the molecular packing is an arrangement of the molecules into two-dimensional sheets that are neither parallel nor orthogonal to any cell axis or face (Fig. 2). Within these sheets, adjacent molecules are juxtaposed in a head-to-head and tail-to-tail fashion such that pseudo twofold rotational symmetry relates them (Fig. 3). An apparent consequence of this pattern is the creation of interchain hydrophobic interactions between pentyloxy groups, which likely assist in supporting their fully extended, linear disposition. Molecules of 2-(pentyloxy)dibenzo[b,d]furan in adjacent sheets enjoy π–π stacking interactions that slightly offset the centroid of the furan ring of one molecule above that of a neighboring molecule such that the centroid-to-centroid distance is 4.070 (3) Å (Fig. 4, red line). The length of the perpendicular segment between adjacent furan rings, defined with one point as a furan centroid, is 3.3731 (12) Å (Fig. 4, blue line). These separations are comparable to the 3.72–3.76 Å distances between molecules in the structure of dibenzofuran itself (Dideberg et al., 1972 ).

Figure 1
The title molecule with the atom-labeling scheme and 50% probability ellipsoids.

Figure 2
Packing of molecules of 2-(pentyloxy)dibenzo[b,d]furan within the unit cell. Displacement ellipsoids are shown at the 50% probability level.

Figure 3
Molecules of 2-(pentyloxy)dibenzo[b,d]furan within a sheet, showing the tail-to-tail arrangement of pentyloxy substituents. Displacement ellipsoids are shown at the 50% probability level.

Figure 4
Molecules of 2-(pentyloxy)dibenzo[b,d]furan in adjacent sheets. The furan ring centroid-to-centroid distance is depicted with the red dashed line, while the separation along a perpendicular from a furan ring centroid is shown in blue. Displacement ellipsoids are shown at the 50% probability level.

Synthesis and crystallization

The starting material, 2-hydroxydibenzofuran (0.10 g, 0.54 mmol), was dissolved in 10 mL of acetone under an N₂ atmosphere. To this solution, solid potassium carbonate was then added (0.3 g, 4 eq.). The reaction mixture was stirred at room temperature for 30 minutes before the dropwise addition of pentyl bromide (0.10 mL, 0.59 mmol). Mild heating to 45°C was applied for 4–5 h, during which time the reaction progress was monitored using thin layer chromatography. The reaction mixture was cooled to room temperature, vacuum filtered, and then taken to dryness under reduced pressure. The crude solid residual was purified by flash chromatography on a silica column eluted with 10:90 EtOAc:hexanes to afford the target compound as a white solid. Crystals were obtained by slow cooling of a warm solution in ethyl acetate:hexanes (2:1, v:v). Yield: 0.35 g, 85%. R_f: 0.80 (10:90 EtOAc:hexanes, UV). ¹H NMR (300 MHz, (δ, ppm in CDCl₃): 7.94 (d, J = 8.2 Hz, 1H), 7.59 (d, J = 8.3 Hz, 1H), 7.52–7.44 (m, 3H), 7.39–7.33 (m, 1H), 7.11–7.06 (m, 1H), 4.09 (t, J = 6.5 Hz, 2H), 1.89 (q, J = 7.2 Hz, 2H), 1.41–1.59 (m, 4H), 1.00 (t, J = 7.1 Hz, 3H). ¹³C NMR (75 MHz, (δ, ppm in CDCl₃): 156.9, 155.4, 150.8 127.0, 124.6, 124.5, 122.4, 120.5, 115.7, 112.0, 104.6, 69.0, 29.1, 28.3, 22.5, 14.1. GC–MS: 254, 183.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	C₁₇H₁₈O₂
M_r	254.31
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	150
a, b, c (Å)	7.841 (4), 8.203 (4), 11.080 (6)
α, β, γ (°)	79.131 (7), 85.616 (6), 74.077 (6)
V (Å³)	672.8 (6)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.08
Crystal size (mm)	0.39 × 0.23 × 0.15

Data collection
Diffractometer	Bruker SMART APEX CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.790, 0.987
No. of measured, independent and observed [I > 2σ(I)] reflections	4601, 1806, 1345
R_int	0.029
θ_max (°)	22.7
(sin θ/λ)_max (Å⁻¹)	0.544

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.052, 0.152, 1.11
No. of reflections	1806
No. of parameters	244
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.24
Computer programs: APEX3 and SAINT (Bruker, 2016 ), SHELXT (Sheldrick, 2015a ), SHELXL2018/1 (Sheldrick, 2015b ) and SHELXTL (Sheldrick, 2008 ).

Structural data

CCDC reference: 1867924

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314618013068/bx4012sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314618013068/bx4012Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314618013068/bx4012Isup3.cml

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/1 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

2-(Pentyloxy)dibenzo[b,d]furan top

Crystal data top

C₁₇H₁₈O₂	Z = 2
M_r = 254.31	F(000) = 272
Triclinic, P1	D_x = 1.255 Mg m⁻³
a = 7.841 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.203 (4) Å	Cell parameters from 2845 reflections
c = 11.080 (6) Å	θ = 2.6–22.7°
α = 79.131 (7)°	µ = 0.08 mm⁻¹
β = 85.616 (6)°	T = 150 K
γ = 74.077 (6)°	Block, colorless
V = 672.8 (6) Å³	0.39 × 0.23 × 0.15 mm

Data collection top

Bruker SMART APEX CCD diffractometer	1806 independent reflections
Radiation source: fine-focus sealed tube	1345 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.029
Detector resolution: 8.3333 pixels mm^-1	θ_max = 22.7°, θ_min = 1.9°
φ and ω scans	h = −8→8
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −8→8
T_min = 0.790, T_max = 0.987	l = −12→11
4601 measured reflections

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)] = 0.052	Hydrogen site location: difference Fourier map
wR(F²) = 0.152	All H-atom parameters refined
S = 1.11	w = 1/[σ²(F_o²) + (0.0701P)² + 0.5606P] where P = (F_o² + 2F_c²)/3
1806 reflections	(Δ/σ)_max < 0.001
244 parameters	Δρ_max = 0.23 e Å⁻³
0 restraints	Δρ_min = −0.24 e Å⁻³

Special details top

Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, collected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = –30.00 and 210.00°. The scan time was 30 sec/frame.

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.

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

	x	y	z	U_iso*/U_eq
O1	0.0899 (2)	0.7991 (2)	0.40165 (18)	0.0332 (6)
O2	0.2926 (2)	0.3931 (3)	0.04899 (18)	0.0349 (6)
C1	−0.0704 (4)	0.7661 (4)	0.4407 (3)	0.0306 (7)
C2	−0.1831 (4)	0.8459 (4)	0.5259 (3)	0.0345 (8)
H2	−0.152 (3)	0.931 (3)	0.559 (2)	0.019 (7)*
C3	−0.3401 (4)	0.8019 (4)	0.5513 (3)	0.0369 (8)
H3	−0.433 (5)	0.856 (4)	0.611 (3)	0.056 (10)*
C4	−0.3820 (4)	0.6819 (4)	0.4941 (3)	0.0351 (8)
H4	−0.504 (4)	0.650 (4)	0.516 (3)	0.033 (7)*
C5	−0.2659 (4)	0.6033 (4)	0.4094 (3)	0.0326 (8)
H5	−0.290 (4)	0.518 (4)	0.369 (3)	0.033 (8)*
C6	−0.1074 (4)	0.6445 (3)	0.3816 (3)	0.0285 (7)
C7	0.0414 (3)	0.5998 (3)	0.2969 (2)	0.0264 (7)
C8	0.0839 (4)	0.4924 (4)	0.2096 (3)	0.0271 (7)
H8	0.005 (4)	0.427 (4)	0.197 (2)	0.027 (7)*
C9	0.2361 (3)	0.4897 (3)	0.1411 (2)	0.0265 (7)
C10	0.3479 (4)	0.5903 (4)	0.1570 (3)	0.0309 (7)
H10	0.454 (4)	0.588 (4)	0.106 (3)	0.033 (8)*
C11	0.3068 (4)	0.6953 (4)	0.2441 (3)	0.0332 (8)
H11	0.387 (3)	0.760 (3)	0.255 (2)	0.018 (6)*
C12	0.1539 (4)	0.6982 (4)	0.3117 (3)	0.0297 (7)
C13	0.2041 (4)	0.2662 (4)	0.0379 (3)	0.0293 (7)
H13A	0.208 (3)	0.182 (4)	0.115 (3)	0.029 (7)*
H13B	0.072 (4)	0.319 (3)	0.023 (2)	0.025 (7)*
C14	0.2947 (4)	0.1780 (4)	−0.0661 (3)	0.0311 (7)
H14B	0.289 (3)	0.264 (3)	−0.139 (3)	0.019 (7)*
H14A	0.423 (4)	0.131 (4)	−0.048 (2)	0.030 (7)*
C15	0.2184 (4)	0.0354 (4)	−0.0873 (3)	0.0321 (7)
H15A	0.220 (3)	−0.045 (4)	−0.009 (3)	0.029 (7)*
H15B	0.091 (4)	0.087 (4)	−0.111 (2)	0.031 (7)*
C16	0.3193 (4)	−0.0593 (4)	−0.1866 (3)	0.0344 (8)
H16B	0.327 (4)	0.024 (4)	−0.264 (3)	0.032 (8)*
H16A	0.447 (4)	−0.110 (3)	−0.163 (2)	0.030 (7)*
C17	0.2355 (5)	−0.1938 (5)	−0.2144 (4)	0.0479 (9)
H17A	0.295 (4)	−0.255 (4)	−0.279 (3)	0.040 (9)*
H17C	0.229 (5)	−0.279 (5)	−0.140 (4)	0.068 (12)*
H17B	0.106 (5)	−0.136 (5)	−0.242 (3)	0.074 (12)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0338 (12)	0.0302 (12)	0.0416 (13)	−0.0115 (9)	0.0012 (9)	−0.0171 (10)
O2	0.0346 (12)	0.0360 (12)	0.0393 (12)	−0.0138 (9)	0.0081 (9)	−0.0164 (10)
C1	0.0280 (16)	0.0264 (16)	0.0365 (17)	−0.0044 (13)	−0.0030 (13)	−0.0062 (14)
C2	0.0376 (18)	0.0279 (17)	0.0403 (19)	−0.0080 (14)	−0.0004 (14)	−0.0131 (15)
C3	0.0377 (18)	0.0330 (18)	0.0382 (19)	−0.0032 (14)	0.0024 (14)	−0.0125 (15)
C4	0.0325 (17)	0.0360 (18)	0.0385 (18)	−0.0098 (14)	0.0043 (14)	−0.0110 (15)
C5	0.0376 (18)	0.0263 (17)	0.0352 (18)	−0.0086 (14)	−0.0004 (14)	−0.0091 (14)
C6	0.0304 (16)	0.0252 (16)	0.0296 (16)	−0.0063 (12)	−0.0038 (13)	−0.0042 (13)
C7	0.0270 (15)	0.0254 (16)	0.0256 (16)	−0.0056 (12)	−0.0026 (12)	−0.0025 (13)
C8	0.0249 (15)	0.0276 (16)	0.0306 (17)	−0.0072 (13)	−0.0001 (12)	−0.0093 (13)
C9	0.0278 (15)	0.0236 (16)	0.0277 (16)	−0.0027 (12)	−0.0044 (12)	−0.0079 (13)
C10	0.0284 (16)	0.0338 (17)	0.0316 (17)	−0.0101 (13)	0.0027 (14)	−0.0073 (14)
C11	0.0310 (17)	0.0324 (17)	0.0398 (19)	−0.0120 (14)	−0.0043 (14)	−0.0085 (15)
C12	0.0300 (16)	0.0265 (16)	0.0324 (17)	−0.0041 (12)	−0.0063 (13)	−0.0072 (14)
C13	0.0312 (17)	0.0242 (16)	0.0353 (19)	−0.0094 (13)	−0.0015 (13)	−0.0085 (14)
C14	0.0309 (18)	0.0268 (17)	0.0354 (19)	−0.0048 (13)	−0.0017 (13)	−0.0087 (15)
C15	0.0322 (18)	0.0289 (17)	0.0357 (19)	−0.0066 (14)	−0.0017 (14)	−0.0087 (15)
C16	0.0365 (19)	0.0305 (18)	0.038 (2)	−0.0077 (14)	−0.0024 (14)	−0.0128 (16)
C17	0.057 (2)	0.041 (2)	0.053 (2)	−0.0146 (18)	−0.0008 (19)	−0.023 (2)

Geometric parameters (Å, º) top

O1—C1	1.378 (3)	C10—C11	1.375 (4)
O1—C12	1.392 (3)	C10—H10	0.96 (3)
O2—C9	1.382 (3)	C11—C12	1.361 (4)
O2—C13	1.428 (3)	C11—H11	0.96 (3)
C1—C2	1.375 (4)	C13—C14	1.504 (4)
C1—C6	1.394 (4)	C13—H13A	0.99 (3)
C2—C3	1.370 (4)	C13—H13B	1.02 (3)
C2—H2	0.94 (3)	C14—C15	1.514 (4)
C3—C4	1.387 (4)	C14—H14B	0.96 (3)
C3—H3	1.01 (4)	C14—H14A	1.00 (3)
C4—C5	1.378 (4)	C15—C16	1.514 (4)
C4—H4	1.06 (3)	C15—H15A	0.99 (3)
C5—C6	1.373 (4)	C15—H15B	1.00 (3)
C5—H5	0.96 (3)	C16—C17	1.516 (4)
C6—C7	1.451 (4)	C16—H16B	1.00 (3)
C7—C8	1.390 (4)	C16—H16A	1.01 (3)
C7—C12	1.386 (4)	C17—H17A	0.97 (3)
C8—C9	1.362 (4)	C17—H17C	0.99 (4)
C8—H8	0.96 (3)	C17—H17B	1.04 (4)
C9—C10	1.399 (4)

C1—O1—C12	105.0 (2)	C10—C11—H11	119.0 (15)
C9—O2—C13	118.3 (2)	C11—C12—O1	125.3 (2)
C2—C1—O1	124.3 (3)	C11—C12—C7	122.9 (3)
C2—C1—C6	123.6 (3)	O1—C12—C7	111.8 (2)
O1—C1—C6	112.1 (2)	O2—C13—C14	107.2 (2)
C3—C2—C1	116.7 (3)	O2—C13—H13A	111.4 (15)
C3—C2—H2	124.2 (15)	C14—C13—H13A	110.9 (16)
C1—C2—H2	119.0 (15)	O2—C13—H13B	112.0 (14)
C2—C3—C4	121.4 (3)	C14—C13—H13B	111.1 (14)
C2—C3—H3	122.5 (19)	H13A—C13—H13B	104 (2)
C4—C3—H3	116.0 (19)	C13—C14—C15	113.5 (2)
C5—C4—C3	120.6 (3)	C13—C14—H14B	108.3 (15)
C5—C4—H4	119.8 (15)	C15—C14—H14B	111.2 (15)
C3—C4—H4	119.6 (15)	C13—C14—H14A	108.4 (16)
C6—C5—C4	119.6 (3)	C15—C14—H14A	109.8 (16)
C6—C5—H5	117.8 (17)	H14B—C14—H14A	105 (2)
C4—C5—H5	122.6 (17)	C16—C15—C14	112.6 (2)
C5—C6—C1	118.1 (3)	C16—C15—H15A	110.3 (16)
C5—C6—C7	136.4 (3)	C14—C15—H15A	107.9 (15)
C1—C6—C7	105.4 (2)	C16—C15—H15B	109.5 (15)
C8—C7—C12	119.6 (2)	C14—C15—H15B	108.6 (16)
C8—C7—C6	134.6 (2)	H15A—C15—H15B	108 (2)
C12—C7—C6	105.8 (2)	C15—C16—C17	112.8 (3)
C9—C8—C7	117.8 (3)	C15—C16—H16B	109.9 (16)
C9—C8—H8	122.2 (16)	C17—C16—H16B	109.1 (16)
C7—C8—H8	120.0 (16)	C15—C16—H16A	108.9 (15)
C8—C9—O2	124.2 (2)	C17—C16—H16A	112.5 (15)
C8—C9—C10	121.8 (3)	H16B—C16—H16A	103 (2)
O2—C9—C10	113.9 (2)	C16—C17—H17A	115.1 (18)
C11—C10—C9	120.3 (3)	C16—C17—H17C	110 (2)
C11—C10—H10	119.5 (17)	H17A—C17—H17C	108 (3)
C9—C10—H10	120.1 (17)	C16—C17—H17B	110 (2)
C12—C11—C10	117.5 (3)	H17A—C17—H17B	106 (3)
C12—C11—H11	123.5 (15)	H17C—C17—H17B	106 (3)

Funding information

Funding for this research was provided by: National Institutes of Health (award No. G12MD007595; award No. TL4GM118968; award No. 5RL5GM118966; award No. R25GM060926); National Science Foundation, Division of Chemistry (grant No. MRI: 1228232; award No. MRI: 0619770); Louisiana Board of Regents (grant No. LEQSF-(2002-03)-ENH-TR-67).

References

Alexander, D. L. & Jefcoate, C. R. (1995). Proc. Amer. Assoc. Cancer Res. 36, 152, abstract 905. Google Scholar
Bruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chiranjeevi, B., Koyyada, T., Prabusreenivasan, S., Kumar, V., Sujitha, P., Kumar, C. G., Sridhar, B., Shaik, S. & Chandrasekharam, M. (2013). RSC Adv. 3, 16475–16485. CrossRef Google Scholar
Cragg, G. M., Newman, D. J. & Snader, K. M. (1997). J. Nat. Prod. 60, 52–60. CrossRef PubMed Google Scholar
Dideberg, O., Dupont, L. & André, J. M. (1972). Acta Cryst. B28, 1002–1007. CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
Foroozesh, M., Jiang, Q., Sridhar, J., Liu, J., Dotson, B. & McClain, E. (2013). J. Undergrad. Chem. Res. 12, 89–91. Google Scholar
Foroozesh, M., Primrose, G., Guo, Z., Bell, L. C., Alworth, W. L. & Guengerich, F. P. (1997). Chem. Res. Toxicol. 10, 91–102. CrossRef CAS PubMed Web of Science Google Scholar
Kantevari, S., Yempala, T., Yogeeswari, P., Sriram, D. & Sridhar, B. (2011). Bioorg. Med. Chem. Lett. 21, 4316–4319. CrossRef PubMed Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sridhar, J., Goyal, N., Liu, J. & Foroozesh, M. (2017). Molecules, 22, 1143/1–1143/19. Google Scholar
Yurttaş, L., Abu Mohsen, U., Ozkan, Y., Cobanoglu, S., Levent, S. & Kaplancikli, Z. A. (2016). J. Enzyme Inhib. Med. Chem. 31, 1177–1183. PubMed Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.