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ISSN: 2414-3146

7-Bromo-1,4-di­butyl-1,2,3,4-tetra­hydro­pyrido[2,3-b]pyrazine-2,3-dione

aLaboratoire de Chimie Organique Appliquée, Université Sidi Mohamed Ben Abdallah, Faculté des Sciences et Techniques, Route d'Imouzzer, BP 2202, Fez, Morocco, bDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA, and cLaboratoire de Chimie Organique Hétérocyclique URAC 21, Pôle de, Compétence Pharmacochimie, Av. Ibn Battouta, BP 1014, Faculté des Sciences, Université Mohammed V, Rabat, Morocco
*Correspondence e-mail: younes.ouzidan@usmba.ac.ma

Edited by O. Blacque, University of Zürich, Switzerland (Received 30 June 2017; accepted 3 July 2017; online 7 July 2017)

In the title compound, C15H20BrN3O2, the butyl substituents are in extended conformations on opposite sides of the bicyclic core. In the crystal, oblique stacks of mol­ecules, formed by offset π-stacking inter­actions between pyridine and pyrazine rings in adjacent mol­ecules, extend along the b-axis direction. The stacks are associated through a combination of C—H⋯O hydrogen bonds and C—Br⋯π(ring) inter­actions.

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

Structure description

Pyrido-pyrazine derivatives are a versatile class of nitro­gen-containing heterocyclic compounds and they constitute useful inter­mediates in organic synthesis and medicinal chemistry. They possess a broad spectrum of biological activities including anti-cancer (Gong et al., 2011[Gong, Y. D., Dong, M. S., Lee, S. B., Kim, N., Bae, M. S. & Kang, N. S. (2011). Bioorg. Med. Chem. 19, 5639-5647.]), anti-inflammatory (Hodgetts et al., 2010[Hodgetts, K. J., Blum, C. A., Caldwell, T., Bakthavatchalam, R., Zheng, X., Capitosti, S., Krause, J. E., Cortright, D., Crandall, M., Murphy, B. A., Boyce, S., Jones, A. B. & Chenard, B. L. (2010). Bioorg. Med. Chem. Lett. 20, 4359-4363.]) and anti­malarial (Richter et al., 2006[Richter, H. G. F., Adams, D. R., Benardeau, A., Bickerdike, M. J., Bentley, J. M., Blench, T. J., Cliffe, I. A., Dourish, C., Hebeisen, P., Kennett, G. A., Knight, A. R., Malcolm, C. S., Mattei, P., Misra, A., Mizrahi, J., Monck, N. J. T., Plancher, J.-M., Roever, S., Roffey, J. R. A., Taylor, S. & Vickers, S. P. (2006). Bioorg. Med. Chem. Lett. 16, 1207-1211.]). They are also used as inhibitors of anaplastic lymphoma kinase (Milkiewicz et al., 2010[Milkiewicz, K. L., Weinberg, L. R., Albom, M. S., Angeles, T. S., Cheng, M., Ghose, A. K., Roemmele, R. C., Theroff, J. P., Underiner, T. L., Zificsak, C. A. & Dorsey, B. D. (2010). Bioorg. Med. Chem. 18, 4351-4362.]). As a continuation of our research in the field of substituted pyrido[2,3-b]pyrazine derivatives (Hjouji et al., 2014[Hjouji, M. Y., Kandri Rodi, Y., Misbahi, K., Ouazzani Chahdi, F., Akhazzane, M. & Essassi, E. M. (2014). J. Mar. Chim. Heterocycl, 13, 65-71.]), we report here the synthesis of the title compound by the condensation of butyl bromide and 7-bromo­pyrido[2,3-b]pyrazine-2,3(1H,4H)-dione.

In the title mol­ecule, the n-butyl substituents are both in extended conformations with one extending above and the other below the pyrazine ring (Fig. 1[link]). The bicyclic core is planar within experimental error.

[Figure 1]
Figure 1
The title mol­ecule with labeling scheme and 50% probability ellipsoids.

In the crystal, the mol­ecules form oblique stacks along the b-axis direction through offset π-stacking inter­actions between the pyridine portion of one mol­ecule and the pyrazine portion of the next (Fig. 2[link]). In the stack, the centroid–centroid distance of the respective rings is 3.695 (5) Å and they are parallel within experimental error. Assisting these inter­actions in forming the stacks are π inter­actions between the C7O2 carbonyl group and the pyridine ring in adjacent mol­ecules (Fig. 2[link]) where the distance between the mid-point of the double bond and the ring centroid is 3.268 (8) Å. Finally, the stacks are associated through a combination of C2—H2⋯O1 and C12—H12A⋯O1 hydrogen bonds (Table 1[link] and Fig. 3[link]) and C3—Br1⋯π(ring)i inter­actions (Fig. 2[link]) where Br1⋯Cg2 = 3.701 (4) Å, C3—Br1⋯Cg2 = 118.1 (3)° and Cg2 is the centroid of the pyrazine portion of the mol­ecule with symmetry code (i) [{1\over 2}] − x, −[{1\over 2}] + y, −[{1\over 2}] + z).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C2—H2⋯O1i 0.95 2.33 3.253 (12) 164
C12—H12A⋯O1i 0.99 2.55 3.447 (11) 150
Symmetry code: (i) [-x+{\script{1\over 2}}, y-{\script{1\over 2}}, z-{\script{1\over 2}}].
[Figure 2]
Figure 2
Detail of the inter­molecular inter­actions (dashed lines), viewed along the a-axis direction (C—H⋯O hydrogen bonds (black), π-stacking (purple), C=O⋯π(ring) (green), C—Br⋯π(ring) (orange)).
[Figure 3]
Figure 3
Packing viewed along the b-axis direction, with C—H⋯O hydrogen bonds shown as black dashed lines.

Synthesis and crystallization

Butyl bromide (0.2 ml, 1.82 mmol) was added to a solution of 7-bromo­pyrido[2,3-b]pyrazine-2,3(1H,4H)-dione (0.2 g, 0.83 mmol), K2CO3 (0.28 g, 2.07 mmol) and tetra-n-butyl ammonium bromide (0.03 g, 0.1 mmol) in DMF (10 ml). The mixture was then stirred for 6 h at room temperature. The solvent was evaporated under reduced pressure and the product isolated by chromatography on a silica gel column with ethyl acetate/hexane (1/2) as eluent. The compound forms pale-blue plate-shaped crystals in 77% yield and was recrystallized from a solvent mixture (ethanol/di­chloro­methane: 2/1).

Refinement

Crystal and refinement details are presented in Table 2[link]. The hydrogen atoms were included as riding contributions in idealized positions.

Table 2
Experimental details

Crystal data
Chemical formula C15H20BrN3O2
Mr 354.25
Crystal system, space group Orthorhombic, Pna21
Temperature (K) 100
a, b, c (Å) 22.569 (6), 5.1097 (13), 13.497 (3)
V3) 1556.5 (7)
Z 4
Radiation type Mo Kα
μ (mm−1) 2.65
Crystal size (mm) 0.22 × 0.21 × 0.02
 
Data collection
Diffractometer Bruker SMART APEX CCD
Absorption correction Multi-scan (SADABS; Bruker, 2016[Bruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.50, 0.96
No. of measured, independent and observed [I > 2σ(I)] reflections 13413, 3859, 2916
Rint 0.091
(sin θ/λ)max−1) 0.676
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.156, 1.06
No. of reflections 3859
No. of parameters 192
No. of restraints 94
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 2.33, −1.38
Absolute structure Flack x determined using 1091 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter 0.038 (15)
Computer programs: APEX3 and SAINT (Bruker, 2016[Bruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), DIAMOND (Brandenburg & Putz, 2012[Brandenburg, K. & Putz, H. (2012). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Structural data


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: SHELXL2014 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

7-Bromo-1,4-dibutyl-1,2,3,4-tetrahydropyrido[2,3-b]pyrazine-2,3-dione top
Crystal data top
C15H20BrN3O2Dx = 1.512 Mg m3
Mr = 354.25Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pna21Cell parameters from 3677 reflections
a = 22.569 (6) Åθ = 2.4–26.1°
b = 5.1097 (13) ŵ = 2.65 mm1
c = 13.497 (3) ÅT = 100 K
V = 1556.5 (7) Å3Plate, pale blue
Z = 40.22 × 0.21 × 0.02 mm
F(000) = 728
Data collection top
Bruker SMART APEX CCD
diffractometer
3859 independent reflections
Radiation source: fine-focus sealed tube2916 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.091
Detector resolution: 8.3333 pixels mm-1θmax = 28.7°, θmin = 1.8°
ω scansh = 2929
Absorption correction: multi-scan
(SADABS; Bruker, 2016)
k = 66
Tmin = 0.50, Tmax = 0.96l = 1817
13413 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.068H-atom parameters constrained
wR(F2) = 0.156 w = 1/[σ2(Fo2) + 6.1176P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max < 0.001
3859 reflectionsΔρmax = 2.33 e Å3
192 parametersΔρmin = 1.38 e Å3
94 restraintsAbsolute structure: Flack x determined using 1091 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.038 (15)
Special details top

Experimental. The diffraction data were collected in three sets of 363 frames (0.5° width in ω) at φ = 0, 120 and 240°. A scan time of 80 sec/frame was used.

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 > 2sigma(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. H-atoms attached to carbon were placed in calculated positions (C—H = 0.95 - 0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.30633 (4)0.15545 (15)0.26770 (7)0.0209 (2)
O10.3211 (3)0.8535 (14)0.7274 (5)0.0249 (16)
O20.2233 (3)0.9499 (14)0.6151 (5)0.0249 (16)
N10.3741 (4)0.1719 (16)0.5238 (6)0.0203 (16)
N20.3449 (4)0.5053 (15)0.6305 (5)0.0180 (16)
N30.2463 (4)0.6115 (14)0.5112 (6)0.0158 (15)
C10.2854 (4)0.4141 (18)0.4835 (7)0.0168 (18)
C20.2764 (5)0.259 (2)0.4013 (7)0.0191 (19)
H20.24220.28210.36120.023*
C30.3178 (4)0.0675 (19)0.3780 (6)0.0193 (19)
C40.3653 (4)0.0215 (19)0.4425 (6)0.0184 (19)
H40.39200.11800.42890.022*
C50.3348 (5)0.3572 (18)0.5437 (6)0.0172 (17)
C60.3103 (4)0.7138 (17)0.6563 (7)0.0168 (18)
C70.2560 (5)0.7737 (18)0.5913 (7)0.0185 (18)
C80.3954 (4)0.4332 (19)0.6961 (7)0.021 (2)
H8A0.40200.24190.69240.026*
H8B0.38540.47760.76550.026*
C90.4524 (5)0.576 (2)0.6662 (7)0.024 (2)
H9A0.46220.53550.59630.029*
H9B0.44640.76780.67170.029*
C100.5036 (5)0.493 (2)0.7330 (8)0.028 (2)
H10A0.49240.52450.80290.033*
H10B0.51030.30280.72480.033*
C110.5613 (5)0.637 (2)0.7113 (10)0.036 (3)
H11A0.57370.60120.64310.055*
H11B0.59210.57700.75720.055*
H11C0.55520.82560.71980.055*
C120.1912 (4)0.661 (2)0.4538 (7)0.0200 (19)
H12A0.19870.62530.38270.024*
H12B0.17990.84730.46050.024*
C130.1406 (4)0.4884 (19)0.4902 (7)0.021 (2)
H13A0.15260.30260.48470.026*
H13B0.13310.52620.56100.026*
C140.0842 (5)0.530 (2)0.4327 (7)0.025 (2)
H14A0.09080.47710.36300.031*
H14B0.07430.71860.43310.031*
C150.0318 (5)0.377 (2)0.4738 (8)0.030 (2)
H15A0.00250.39970.43020.046*
H15B0.02210.44110.54030.046*
H15C0.04200.19050.47740.046*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0338 (5)0.0191 (4)0.0099 (3)0.0011 (4)0.0012 (6)0.0072 (5)
O10.035 (4)0.027 (4)0.012 (3)0.005 (3)0.002 (3)0.013 (3)
O20.035 (4)0.020 (4)0.020 (4)0.003 (3)0.004 (3)0.002 (3)
N10.024 (4)0.022 (4)0.015 (3)0.002 (3)0.002 (3)0.000 (3)
N20.029 (4)0.016 (4)0.009 (3)0.003 (3)0.001 (3)0.005 (3)
N30.025 (4)0.012 (3)0.010 (3)0.001 (3)0.001 (3)0.003 (3)
C10.023 (4)0.016 (4)0.011 (4)0.001 (3)0.002 (3)0.002 (3)
C20.028 (5)0.019 (4)0.010 (4)0.001 (4)0.000 (4)0.000 (3)
C30.030 (5)0.021 (4)0.007 (4)0.001 (3)0.004 (3)0.002 (3)
C40.028 (5)0.018 (4)0.010 (4)0.001 (4)0.001 (3)0.002 (3)
C50.025 (4)0.018 (4)0.009 (3)0.000 (3)0.000 (3)0.002 (3)
C60.029 (4)0.010 (4)0.011 (3)0.004 (3)0.001 (3)0.002 (3)
C70.029 (5)0.018 (4)0.009 (3)0.001 (3)0.001 (3)0.000 (3)
C80.030 (6)0.025 (5)0.009 (4)0.002 (4)0.002 (4)0.005 (4)
C90.031 (6)0.023 (5)0.017 (5)0.000 (4)0.002 (4)0.001 (4)
C100.036 (6)0.024 (5)0.023 (5)0.001 (4)0.005 (4)0.001 (4)
C110.031 (6)0.031 (6)0.047 (7)0.001 (5)0.009 (5)0.003 (5)
C120.023 (5)0.025 (5)0.013 (4)0.002 (4)0.005 (4)0.001 (4)
C130.026 (6)0.022 (5)0.016 (5)0.005 (4)0.000 (4)0.006 (4)
C140.034 (6)0.025 (5)0.017 (5)0.002 (5)0.001 (4)0.002 (4)
C150.031 (6)0.036 (6)0.024 (5)0.003 (5)0.001 (5)0.006 (5)
Geometric parameters (Å, º) top
Br1—C31.892 (9)C9—C101.527 (15)
O1—C61.221 (11)C9—H9A0.9900
O2—C71.207 (12)C9—H9B0.9900
N1—C51.325 (12)C10—C111.523 (15)
N1—C41.354 (12)C10—H10A0.9900
N2—C61.365 (12)C10—H10B0.9900
N2—C51.414 (11)C11—H11A0.9800
N2—C81.489 (12)C11—H11B0.9800
N3—C71.379 (12)C11—H11C0.9800
N3—C11.392 (11)C12—C131.525 (14)
N3—C121.487 (12)C12—H12A0.9900
C1—C21.380 (13)C12—H12B0.9900
C1—C51.408 (14)C13—C141.506 (14)
C2—C31.388 (14)C13—H13A0.9900
C2—H20.9500C13—H13B0.9900
C3—C41.402 (14)C14—C151.523 (15)
C4—H40.9500C14—H14A0.9900
C6—C71.537 (14)C14—H14B0.9900
C8—C91.535 (14)C15—H15A0.9800
C8—H8A0.9900C15—H15B0.9800
C8—H8B0.9900C15—H15C0.9800
C5—N1—C4118.2 (8)C8—C9—H9B109.6
C6—N2—C5122.4 (8)H9A—C9—H9B108.1
C6—N2—C8118.7 (7)C11—C10—C9113.5 (9)
C5—N2—C8118.9 (8)C11—C10—H10A108.9
C7—N3—C1123.1 (8)C9—C10—H10A108.9
C7—N3—C12116.0 (8)C11—C10—H10B108.9
C1—N3—C12120.9 (8)C9—C10—H10B108.9
C2—C1—N3122.6 (9)H10A—C10—H10B107.7
C2—C1—C5117.5 (9)C10—C11—H11A109.5
N3—C1—C5119.7 (8)C10—C11—H11B109.5
C1—C2—C3119.2 (9)H11A—C11—H11B109.5
C1—C2—H2120.4C10—C11—H11C109.5
C3—C2—H2120.4H11A—C11—H11C109.5
C2—C3—C4119.5 (9)H11B—C11—H11C109.5
C2—C3—Br1120.6 (7)N3—C12—C13111.1 (8)
C4—C3—Br1119.5 (7)N3—C12—H12A109.4
N1—C4—C3121.3 (9)C13—C12—H12A109.4
N1—C4—H4119.3N3—C12—H12B109.4
C3—C4—H4119.3C13—C12—H12B109.4
N1—C5—C1124.0 (8)H12A—C12—H12B108.0
N1—C5—N2116.3 (8)C14—C13—C12112.7 (8)
C1—C5—N2119.7 (8)C14—C13—H13A109.0
O1—C6—N2122.8 (9)C12—C13—H13A109.0
O1—C6—C7119.4 (8)C14—C13—H13B109.0
N2—C6—C7117.8 (8)C12—C13—H13B109.0
O2—C7—N3124.0 (9)H13A—C13—H13B107.8
O2—C7—C6118.9 (8)C13—C14—C15113.4 (9)
N3—C7—C6117.0 (8)C13—C14—H14A108.9
N2—C8—C9111.6 (8)C15—C14—H14A108.9
N2—C8—H8A109.3C13—C14—H14B108.9
C9—C8—H8A109.3C15—C14—H14B108.9
N2—C8—H8B109.3H14A—C14—H14B107.7
C9—C8—H8B109.3C14—C15—H15A109.5
H8A—C8—H8B108.0C14—C15—H15B109.5
C10—C9—C8110.3 (8)H15A—C15—H15B109.5
C10—C9—H9A109.6C14—C15—H15C109.5
C8—C9—H9A109.6H15A—C15—H15C109.5
C10—C9—H9B109.6H15B—C15—H15C109.5
C7—N3—C1—C2177.7 (9)C5—N2—C6—O1174.9 (9)
C12—N3—C1—C21.5 (14)C8—N2—C6—O14.6 (14)
C7—N3—C1—C56.0 (14)C5—N2—C6—C74.5 (13)
C12—N3—C1—C5174.8 (9)C8—N2—C6—C7176.1 (8)
N3—C1—C2—C3179.3 (9)C1—N3—C7—O2178.2 (9)
C5—C1—C2—C34.3 (14)C12—N3—C7—O21.1 (14)
C1—C2—C3—C45.2 (15)C1—N3—C7—C65.1 (13)
C1—C2—C3—Br1178.5 (7)C12—N3—C7—C6175.7 (8)
C5—N1—C4—C33.2 (13)O1—C6—C7—O23.9 (14)
C2—C3—C4—N14.7 (14)N2—C6—C7—O2176.8 (9)
Br1—C3—C4—N1178.1 (7)O1—C6—C7—N3179.2 (9)
C4—N1—C5—C12.4 (14)N2—C6—C7—N30.1 (12)
C4—N1—C5—N2178.5 (8)C6—N2—C8—C989.8 (10)
C2—C1—C5—N13.0 (15)C5—N2—C8—C989.6 (10)
N3—C1—C5—N1179.5 (9)N2—C8—C9—C10178.6 (8)
C2—C1—C5—N2177.9 (9)C8—C9—C10—C11177.1 (9)
N3—C1—C5—N21.4 (14)C7—N3—C12—C1393.8 (10)
C6—N2—C5—N1175.3 (8)C1—N3—C12—C1387.0 (10)
C8—N2—C5—N14.1 (12)N3—C12—C13—C14179.1 (8)
C6—N2—C5—C13.8 (13)C12—C13—C14—C15175.0 (8)
C8—N2—C5—C1176.8 (9)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O1i0.952.333.253 (12)164
C12—H12A···O1i0.992.553.447 (11)150
Symmetry code: (i) x+1/2, y1/2, z1/2.
 

Acknowledgements

JTM thanks Tulane University for support of the Tulane Crystallography Laboratory.

References

First citationBrandenburg, K. & Putz, H. (2012). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationBruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationGong, Y. D., Dong, M. S., Lee, S. B., Kim, N., Bae, M. S. & Kang, N. S. (2011). Bioorg. Med. Chem. 19, 5639–5647.  Web of Science CrossRef CAS PubMed Google Scholar
First citationHjouji, M. Y., Kandri Rodi, Y., Misbahi, K., Ouazzani Chahdi, F., Akhazzane, M. & Essassi, E. M. (2014). J. Mar. Chim. Heterocycl, 13, 65–71.  Google Scholar
First citationHodgetts, K. J., Blum, C. A., Caldwell, T., Bakthavatchalam, R., Zheng, X., Capitosti, S., Krause, J. E., Cortright, D., Crandall, M., Murphy, B. A., Boyce, S., Jones, A. B. & Chenard, B. L. (2010). Bioorg. Med. Chem. Lett. 20, 4359–4363.  Web of Science CrossRef CAS PubMed Google Scholar
First citationMilkiewicz, K. L., Weinberg, L. R., Albom, M. S., Angeles, T. S., Cheng, M., Ghose, A. K., Roemmele, R. C., Theroff, J. P., Underiner, T. L., Zificsak, C. A. & Dorsey, B. D. (2010). Bioorg. Med. Chem. 18, 4351–4362.  Web of Science CrossRef CAS PubMed Google Scholar
First citationParsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationRichter, H. G. F., Adams, D. R., Benardeau, A., Bickerdike, M. J., Bentley, J. M., Blench, T. J., Cliffe, I. A., Dourish, C., Hebeisen, P., Kennett, G. A., Knight, A. R., Malcolm, C. S., Mattei, P., Misra, A., Mizrahi, J., Monck, N. J. T., Plancher, J.-M., Roever, S., Roffey, J. R. A., Taylor, S. & Vickers, S. P. (2006). Bioorg. Med. Chem. Lett. 16, 1207–1211.  Web of Science CSD CrossRef PubMed CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar

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