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ISSN: 2056-9890

4-Nitro­benzyl 3,4-bis­­(acet­yl­oxy)-2-(4-meth­­oxy­phen­yl)pyrrolidine-1-carboxyl­ate: crystal structure, Hirshfeld surface analysis and computational chemistry

aLaboratório de Cristalografia, Esterodinâmica e Modelagem Molecular, Departamento de Química, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil, bDepartmento de Física, Universidade Federal de São Carlos, 13565-905 São Carlos, SP, Brazil, cInstituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil, dInstituto de Química, Universidade Estadual de Campinas, UNICAMP, C.P. 6154, CEP 13084-917 Campinas, Brazil, and eResearch Centre for Crystalline Materials, School of Science and Technology, Sunway University, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia
*Correspondence e-mail: ignez@df.ufscar.br

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 10 June 2020; accepted 11 June 2020; online 16 June 2020)

The title compound, C23H24N2O9, is a tetra-substituted pyrrolidine derivative with a twisted conformation, with the twist evident in the C—C bond bearing the adjacent acet­yloxy substituents. These are flanked on one side by a C-bound 4-meth­oxy­phen­yl group and on the other by a methyl­ene group. The almost sp2-N atom [sum of angles = 357°] bears a 4-nitro­benzyl­oxycarbonyl substituent. In the crystal, ring-methyl­ene-C—H⋯O(acet­yloxy-carbon­yl) and methyl­ene-C—H⋯O(carbon­yl) inter­actions lead to supra­molecular layers lying parallel to ([\overline{1}]01); the layers stack without directional inter­actions between them. The analysis of the calculated Hirshfeld surfaces indicates the combined importance of H⋯H (42.3%), H⋯O/O⋯H (37.3%) and H⋯C/C⋯H (14.9%) surface contacts. Further, the inter­action energies, largely dominated by the dispersive term, point to the stabilizing influence of H⋯H and O⋯O contacts in the inter-layer region.

1. Chemical context

The structure of the title tetra-substituted pyrrolidine deriv­ative, (I)[link], was determined in connection with our on-going structural studies characterizing key synthetic inter­mediates in the synthesis of various α-glucosidase inhibitors (Zukerman-Schpector et al., 2017[Zukerman-Schpector, J., Sugiyama, F. H., Garcia, A. L. L., Correia, C. R. D., Jotani, M. M. & Tiekink, E. R. T. (2017). Acta Cryst. E73, 1218-1222.]; Dallasta Pedroso et al., 2020[Dallasta Pedroso, S., Caracelli, I., Zukerman-Schpector, J., Soto-Monsalve, M., De Almeida Santos, R. H., Correia, C. R. D., Llanes Garcia, A. L., Kwong, H. C. & Tiekink, E. R. T. (2020). Acta Cryst. E76, 967-972.]). α-Glucosidase inhibitors are an important class of drugs employed in the treatment of a variety of diseases such as cancer, cystic fibrosis, diabetes and influenza (Kiappes et al., 2018[Kiappes, J. L., Hill, M. L., Alonzi, D. S., Miller, J. L., Iwaki, R., Sayce, A. C., Caputo, A. T., Kato, A. & Zitzmann, N. (2018). Chem. Biol. 13, 60-65.]; Dhameja & Gupta, 2019[Dhameja, M. & Gupta, P. (2019). Eur. J. Med. Chem. 176, article No. 343e377.]).

[Scheme 1]

More specifically, (I)[link] was generated during a study designed to synthesize the hy­droxy­lated proline derivative, (2R,3S,4R)-3,4-di­hydroxy­pyrrolidine-2-carb­oxy­lic acid, (II) (Garcia, 2008[Garcia, A. L. L. (2008). PhD thesis, Universidade Estadual de Campinas, UNICAMP, Campinas, SP, Brazil.]). In addition to being an α-glucosidase inhibitor, (II) is also found as a sub-structure of natural bioactive compounds such as, for example, a component of the repeated deca-peptide sequence of the adhesive protein Mytilus edulis foot protein 1 (Mefp1), which is produced by the marine mussel Mytilus edulis and is responsible for the fixation capacity of the mussel to rock (Taylor & Weir, 2000[Taylor, C. M. & Weir, C. A. (2000). J. Org. Chem. 65, 1414-1421.]). The synthetic study determined that in the final stages of the reaction sequence towards (II), it was not possible to smoothly remove the N-bound 4-nitro­benzyl­oxycarbonyl (PNZ) protecting group via catalytic hydrogenation as the ensuing mixture was difficult to purify. Therefore, it proved necessary to remove the PNZ protecting group through acid hydrolysis at reflux temperature, resulting in a low overall yield (34%) suggesting that there was no advantage in using PNZ.

The crystal and mol­ecular structures of (I)[link] are described herein with this experimental study complemented by a detailed analysis of the mol­ecular packing by a combination of Hirshfeld surface analysis, non-covalent inter­action plots and computational chemistry.

2. Structural commentary

The mol­ecular structure of (I)[link], Fig. 1[link], is constructed about a tetra-substituted pyrrolidine ring with a N1-bound (4-nitro­phen­yl)ethyl­carboxyl­ate group and, respectively, C1–C3-bound 4-meth­oxy­phenyl, acet­yloxy and acet­yloxy substituents. For the illustrated mol­ecule, Fig. 1[link], the chirality of the C1–C3 atoms follows the sequence R, R and S, but it is noted that due crystal symmetry, the centrosymmetric unit cell contains equal numbers of the enanti­omers. The conformation of the five-membered ring is twisted about the C2—C3 bond with the C1—C2—C3—C4 torsion angle being 39.70 (16)°, consistent with a (+)syn-clinal configuration. The sum of the angles about the N1 atom is 356.7°, indicating an approximate sp2 centre. The N1-bound group occupies an equatorial position with those at the C1–C3 centres being bis­ectional, equatorial and axial, respectively (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]). When viewed towards the approximate plane through the pyrrolidine ring, the N-bound carboxyl­ate group is approximately co-planar, i.e. excluding the nitro­benzene residue. The C1-substituent lies to the opposite side of the plane than the C2 and C3-acet­yloxy groups; the dihedral angle between the acet­yloxy CO2 planes is 57.7 (2)°.

[Figure 1]
Figure 1
The mol­ecular structure of (I)[link], showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level.

With respect to the least-squares plane through the pyrrolidine ring, the nitro­benzene and meth­oxy­benzene rings are splayed, as seen in the dihedral angles of 58.58 (8) and 77.65 (6)°, respectively; the dihedral angle between the benzene rings is 50.56 (5)°. There is a twist in the nitro­benzene ring as seen in the value of the C11—C10—N2—O4 torsion angle of 17.7 (3)°. By contrast, the meth­oxy group is co-planar with the ring to which it is connected, as shown by the C15—C16—O5—C19 torsion angle of 176.2 (2)°.

3. Supra­molecular features

The only directional non-covalent inter­actions of note in the crystal of (I)[link] are two weak C—H⋯O contacts as listed in Table 1[link]. The presence of ring-methyl­ene-C4—H⋯O7(acet­yloxy-carbon­yl) inter­actions lead to helical chains along the b-axis direction, being propagated by 21 symmetry. The other inter­actions falling within the distance criteria of PLATON (Spek, 2020[Spek, A. L. (2020). Acta Cryst. E76, 1-11.]) are methyl­ene-C6—H⋯O1(carbon­yl) inter­actions, formed between centrosymmetrically related (4-nitro­phen­yl)ethyl­carboxyl­ate groups, which lead to the formation of ten-membered {⋯OCOCH}2 synthons. These serve to connect the helical chains into a layer lying parallel to ([\overline{1}]01), Fig. 2[link](a). A view of the unit-cell contents is shown in Fig. 2[link](b), highlighting the stacking of layers, without directional inter­actions between them.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C4—H4B⋯O7i 0.97 2.60 3.129 (2) 115
C6—H6A⋯O1ii 0.97 2.54 3.250 (2) 130
Symmetry codes: (i) [-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]; (ii) -x+1, -y, -z+2.
[Figure 2]
Figure 2
Mol­ecular packing in (I)[link]: (a) supra­molecular layer parallel to ([\overline{1}]01) sustained by methyl­ene-C—H⋯O(carbon­yl) contacts shown as orange dashed lines (non-participating H atoms are omitted) and (b) view of the unit-cell contents shown in projection down the b axis.

4. Non-covalent inter­action plots

The aforementioned weak C—H⋯O contacts identified in Supra­molecular features were also evaluated by calculating non-covalent inter­action plots (Johnson et al., 2010[Johnson, E. R., Keinan, S., Mori-Sánchez, P., Contreras-García, J., Cohen, A. J. & Yang, W. (2010). J. Am. Chem. Soc. 132, 6498-6506.]; Contreras-García et al., 2011[Contreras-García, J., Johnson, E. R., Keinan, S., Chaudret, R., Piquemal, J.-P., Beratan, D. N. & Yang, W. (2011). J. Chem. Theory Comput. 7, 625-632.]). In short, these calculations indicate whether non-bonding contacts are attractive, weakly attractive or repulsive. The methyl­ene-C6—H⋯O1(carbon­yl) inter­actions giving rise to the ten-membered {⋯OCOCH}2 synthons are highlighted in the upper view of Fig. 3[link](a) with the green isosurface between the inter­acting atoms and the distinctive blue feature in the reduced density gradient (RDG) versus sign(λ2)ρ(r) plot in the lower view, i.e. indicating the density value is less than 0.0 a.u., suggest these inter­actions are weakly attractive. The same is true for the ring-methyl­ene-C4—H⋯O7(acet­yloxy-carbon­yl) inter­actions that lead to the helical chain, Fig. 3[link](b).

[Figure 3]
Figure 3
Non-covalent inter­action plots for the following inter­actions in (I)[link]: (a) methyl­ene-C6—H⋯O1(carbon­yl) and (b) ring-methyl­ene-C4—H⋯O7(acet­yloxy-carbon­yl).

5. Hirshfeld surface analysis

The Hirshfeld surface analysis of (I)[link] involved the calculation of the dnorm-surface plots, electrostatic potential (calculated using the STO-3G basis set at the Hartree–Fock level of theory) and two-dimensional fingerprint plots following literature procedures (Tan et al., 2019[Tan, S. L., Jotani, M. M. & Tiekink, E. R. T. (2019). Acta Cryst. E75, 308-318.]) using Crystal Explorer 17 (Turner et al., 2017[Turner, M. J., Mckinnon, J. J., Wolff, S. K., Grimwood, D. J., Spackman, P. R., Jayatilaka, D. & Spackman, M. A. (2017). Crystal Explorer 17. The University of Western Australia.]). The weak methyl­ene-C6—H⋯O1(carbon­yl) inter­actions are reflected as bright-red spots near the methyl­ene-H6A and carbonyl-O1 atoms on the dnorm-surface plot of (I)[link] shown in Fig. 4[link]. Additional diffuse red spots are also noted near the meth­oxy-O5 and carbonyl-O7 atoms in Fig. 4[link], which reflect their participation in short C5⋯O5 and C4⋯O7 contacts with separations ∼0.1 Å shorter than the sum of their van der Waals radii, Table 2[link]. Further, faint spots near atom H4B as well as the O5 and O7 atoms (each difficult to discern in Fig. 4[link]) are attributed to methyl­ene-C4—H4B⋯O7(carbon­yl) and O2⋯O5 short contacts, being ∼0.02 Å shorter than their respective sums of the van der Waals radii, Table 2[link].

Table 2
Summary of short inter­atomic contacts (Å) in (I)a

Contact Distance Symmetry operation
C6—H6A⋯O1b 2.47 x + 1, −y, −z + 2
C4—H4B⋯O7b 2.55 x + [{1\over 2}], y − [{1\over 2}], −z + [{3\over 2}]
C4⋯O7 3.13 x + [{1\over 2}], y + [{1\over 2}], −z + [{3\over 2}]
C5⋯O5 3.08 x, y − 1, z
O2⋯O5 3.02 x, y − 1, z
C6—H6B⋯C15 2.73 x + 1, −y + 1, −z + 2
C9—H9⋯C21 2.75 x + [{1\over 2}], −y + [{1\over 2}], z + [{1\over 2}]
O4⋯O4 2.75 x + [{3\over 2}], −y + [{3\over 2}], −z + 2
H17⋯H23B 2.35 x + 1, y + 1, −z + [{3\over 2}]
Notes: (a) The inter­atomic distances are calculated in Crystal Explorer 17 (Turner et al., 2017[Turner, M. J., Mckinnon, J. J., Wolff, S. K., Grimwood, D. J., Spackman, P. R., Jayatilaka, D. & Spackman, M. A. (2017). Crystal Explorer 17. The University of Western Australia.]) whereby the X—H bond lengths are adjusted to their neutron values. (b) These inter­actions correspond to the inter­actions listed in Table 1[link].
[Figure 4]
Figure 4
A view of the Hirshfeld surface mapped for (I)[link] over dnorm in the range −0.090 to +1.583 arbitrary units showing the C—H⋯O inter­actions as black dashed lines.

In the views of Fig. 5[link], the faint red spots that appear near the methyl­ene (H6B), benzyl (C15 and H9), methyl (C21) and nitro (O4) atoms correspond to long-range intra-layer methyl­ene-C6—H6B⋯C15(benz­yl), benzyl-C9—H9⋯C21(meth­yl) inter­actions and inter-layer O4⋯O4 short contacts, Table 2[link]. The Hirshfeld surface mapped over the electrostatic potential in Fig. 6[link] highlights the donors and acceptors of the indicated inter­actions through blue (positive electrostatic potential) and red (negative electrostatic potential), respectively.

[Figure 5]
Figure 5
Two views of the Hirshfeld surface mapped over dnorm for (I)[link] in the range −0.090 to +1.583 arbitrary units, highlighting evidence for long-range C—H⋯C inter­actions and O⋯O short contacts within red circles (see text).
[Figure 6]
Figure 6
A view of the Hirshfeld surface mapped over the calculated electrostatic potential for (I)[link]. The potentials were calculated using the STO-3 G basis set at the Hartree–Fock level of theory over a range of −0.067 to 0.040 a.u. The red and blue regions represent negative and positive electrostatic potentials, respectively.

As illustrated in Fig. 7[link](a), the two-dimensional fingerprint plot for the Hirshfeld surface of (I)[link] is shown in the upper left and lower right sides of the de and di diagonal axes, and those delineated into H⋯H, H⋯O/O⋯H, H⋯C/C⋯H, O⋯O and O⋯C/C⋯O contacts are illustrated in Fig. 7[link](b)–(f), respectively. The percentage contributions from different inter­atomic contacts are summarized in Table 3[link]. The H⋯H contacts contribute 42.3% to the overall Hirshfeld surface with the shortest contact, manifested in the round-shape peak tipped at de = di ∼2.4 Å, Fig. 7[link](b), corresponding to the H17⋯H23B inter-layer contact listed in Table 2[link]. The H⋯O/O⋯H contacts contribute 37.3% to the overall Hirshfeld surface, reflecting the significant C—H⋯O contacts evident in the packing, Tables 1[link] and 2[link]. The shortest contacts are reflected as two sharp spikes at de + di ∼2.5 Å in Fig. 7[link](c). The H⋯C/C⋯H contacts that match the long-range C—H⋯C inter­actions discussed above are shown as a pairs of forceps-like tips at de + di ∼2.7 Å in the fingerprint plot delineated into H⋯C/C⋯H contacts, Fig. 7[link](d). Although both O⋯O and O⋯C/C⋯O contacts appear at de + di ∼3.0 Å in the respective fingerprint plots, Fig. 7[link](e) and (f), their contributions to the overall Hirshfeld surface are only 2.1 and 1.2%, respectively. The other inter­atomic contacts have a negligible effect on the mol­ecular packing as their accumulated contribution is about 2.2%.

Table 3
Percentage contributions of inter­atomic contacts to the Hirshfeld surface for (I)

Contact Percentage contribution
H⋯H 42.3
H⋯O/O⋯H 37.3
H⋯C/C⋯H 14.9
O⋯O 2.1
O⋯C/C⋯O 1.2
Others 2.2
[Figure 7]
Figure 7
(a) The full two-dimensional fingerprint plot for (I)[link] and (b)–(f) those delineated into H⋯H, H⋯O/O⋯H, H⋯C/C⋯H, O⋯O and O⋯C/C⋯O contacts, respectively.

6. Energy frameworks

The pairwise inter­action energies between the mol­ecules in the crystal of (I)[link] were calculated by summing up four energy components, comprising the electrostatic (Eele), polarization (Epol), dispersion (Edis) and exchange-repulsion (Erep) energies as per the literature (Turner et al., 2017[Turner, M. J., Mckinnon, J. J., Wolff, S. K., Grimwood, D. J., Spackman, P. R., Jayatilaka, D. & Spackman, M. A. (2017). Crystal Explorer 17. The University of Western Australia.]). In the present study, the energy framework of (I)[link] was generated by employing the 6-31G(d,p) basis set with the B3LYP function. The individual energy components as well as the total inter­action energies are collated in Table 4[link]. As anti­cipated, the dispersive component makes the major contribution to the inter­action energies owing to the absence of conventional hydrogen bonding in the crystal. The most significant stabilization energies are found in the intra-layer region and arise from the directional contacts outlined in Hirshfeld surface analysis as well as two additional C—H⋯O inter­actions, i.e. methyl­ene-C4—H4A⋯O4(nitro) and methyl-C21—H21C⋯O4(nitro) with H⋯O separations of 2.63 and 2.77 Å, respectively.

Table 4
Summary of inter­action energies (kJ mol−1) calculated for (I)[link]

Contact R (Å) Eele Epol Edis Erep Etot
Intra-layer region            
C4—H4B⋯O7i +            
C4⋯O7i 10.99 −17.8 −6.1 −29.1 18.3 −37.3
C6—H6A⋯O1ii 9.21 −23.8 −6.9 −23.2 21.7 −37.0
C5⋯O5iii +            
O2⋯O5iii 8.29 −8.4 −2.7 −56.3 29.1 −41.8
C9—H9⋯C21iv 14.12 −12.7 −3.4 −20.5 12.0 −26.4
C6—H6B⋯C15v +            
C4—H4A⋯O4v 6.55 −18.1 −4.5 −87.1 52.8 −65.8
C21—H21C⋯O4vi 15.04 −2.1 −1.0 −3.7 1.5 −5.2
Inter-layer region            
H17⋯H23Bvii 10.38 2.9 −1.2 −16.5 8.2 −7.1
H17⋯H21Bvii +            
H18⋯H21Bviii 6.24 −1.1 −1.6 −52.9 23.0 −34.2
O4⋯O4ix 13.71 −16.1 −4.4 −16.2 10.8 −27.7
C8—H8⋯O3x 12.70 −5.4 −1.3 −10.2 1.9 −14.4
Symmetry codes: (i) −x + [{1\over 2}], y − [{1\over 2}], −z + [{3\over 2}]; (ii) −x + 1, −y, −z + 2; (iii) x, y − 1, z; (iv) x + [{1\over 2}], −y + [{1\over 2}], z + [{1\over 2}]; (v) −x + 1, −y + 1, −z + 2; (vi) x − [{1\over 2}], −y + [{3\over 2}], z − [{1\over 2}]; (vii) −x + 1, y + 1, − z + [{3\over 2}]; (viii) −x + 1, y, −z + [{3\over 2}]; (ix) −x + [{3\over 2}], −y + [{3\over 2}], −z + 2; (x) −x + [{3\over 2}], −y + [{1\over 2}], −z + 2.

The stabilization energies in the inter-layer region are also dominated by the Edis terms associated with the H⋯H contacts as well as the long-range C—H⋯O inter­actions (−14.4 kJ mol−1). For the former, the maximum energy is not found for the shortest H17⋯H23B contact (−7.1 kJ mol−1), Table 2[link] and Fig. 8[link](b), but rather for a pair of benzene-H⋯H(meth­yl) inter­actions occurring in close proximity in a hydrogen-rich region but at longer separations (−34.2 kJ mol−1). For the inter-layer O4⋯O4 contact mentioned above, there are almost equal contributions from Eele and Edis, Table 4[link], giving rise to a total inter­action energy of −27.7 kJ mol−1. The magnitudes of inter­molecular energies are represented graphically in Fig. 8[link], and clearly demonstrate the dominance of the Edis in the mol­ecular packing.

[Figure 8]
Figure 8
Perspective views of the energy frameworks calculated for (I)[link] and viewed down the b axis showing (a) electrostatic potential force, (b) dispersion force and (c) total energy. The radii of the cylinders are proportional to the relative magnitudes of the corresponding energies and were adjusted to the same scale factor of 50 with a cut-off value of 5 kJ mol−1 within 1 × 1 × 1 unit cells.

7. Database survey

There are relatively few related structures having a similar substitution pattern to the tetra-substituted pyrrolidine ring of (I)[link]. The chemical diagrams for the two most closely related structures, (III), which has two hydroxyl substituents rather than acet­yloxy (ALAVOA; Qian et al., 2016[Qian, B.-C., Kamori, A., Kinami, K., Kato, A., Li, Y.-X., Fleet, G. W. J. & Yu, C.-Y. (2016). Org. Biomol. Chem. 14, 4488-4498.]), and (IV), which has more complex substituents (RAJDUC; Coleman et al., 2004[Coleman, R. S., Felpin, F.-X. & Chen, W. (2004). J. Org. Chem. 69, 7309-7316.]), are shown in Fig. 9[link].

[Figure 9]
Figure 9
Chemical diagrams for (III) and (IV).

8. Synthesis and crystallization

To a solution of 4-nitro­benzyl (2S,3S,4R)-3,4-dihy­droxy-2-(4-meth­oxy­phen­yl)pyrrolidine-1-carboxyl­ate (602 mg, 1.55 mmol) in CH2Cl2 (15 ml) were added pyridine (0.80 ml, 18.584 mmol), acetic anhydride (3.00 ml, 31.8 mmol) and N,N-dimethyl-4-amino­pyridine (2.00 mg, 0.0164 mmol). The solution was stirred for 2 h at room temperature, concentrated in a rota-evaporator and the residue dissolved in EtOAc (10 ml). The resulting solution was washed with a HCl 5% solution (3 × 5 ml) and with saturated solutions of NaHCO3 (2 × 5 ml) and of NaCl (5 ml). The phases were separated and the organic phase was dried with anhydrous Na2SO4, filtered and concentrated in vacuo.

The residue was purified by flash column chromatography in silica gel, using an EtOAc/n-hexane elution gradient (1:3 and 1:2). Yield: 716 mg (98%). Colourless irregular crystals for the X-ray analysis were obtained by the slow evaporation of its n-hexane solution. M.p. 409.5–410.5 K. The 1H and 13C{1H} NMR reflect the presence of two conformational rotamers in solution. 1H NMR (500 MHz, C6D6): δ = 7.75 (d, J = 7.3 Hz, 0.4H); 7.65 (d, J = 7.9 Hz, 1.2H); 7.18 (m, 1.9H); 6.99 (d, J = 7.9 Hz, 1.1H); 6.76 (d, J = 7.0 Hz, 0.5H); 6.72 (d, J = 7.3 Hz, 0.6H); 6.65 (d, J = 7.9 Hz, 1.3H); 6.37 (d, J = 9.3 Hz, 1H); 5.42 (s, 0.2H); 5.33 (m, 1.9H); 5.00 (s, 0.5H); 4.92 (d, J = 13.7 Hz, 0.6H); 4.74 (s, 0.6H); 4.44 (d, J = 13.7 Hz, 0.6H); 3.89 (m, 1.8H); 3.72 (s, 0.3H); 3.29 (s, 3H); 3.35–3.23 (m, 0.3H); 1.61–1.60 (2s, 6H). 1H NMR (500 MHz, CDCl3, TMS r.t.): δ = 8.23 (d, J = 8.2 Hz, 0.6H); 8.00 (d, J = 8.2 Hz, 1.2H); 7.53 (d, J = 7.9 Hz, 0.7H); 7.16 (m, 2H); 6.96 (d, J = 8.5 Hz, 1.2H); 6.88 (d, J = 8.5 Hz, 2.0H); 5.45–5.32 (m, 1H); 5.31–5.18 (m, 2.3H); 5.01–4.87 (m, 1.6H); 4.13 (m, 0.3H); 4.06 (dd, J = 11.6 Hz and 6.4 Hz, 0.7H); 3.85–3.67 (s + m, 4.1H); 2.12-2.07 (4s, 6H). 13C{1H} NMR (125 MHz, CDCl3, r.t.): δ = 169.9; 169.8; 159.4; 159.2; 154.2; 154.1; 147.6; 147.2; 143.6; 143.4; 130.6; 129.4; 128.1; 127.5; 126.8; 126.7; 123.7; 123.4; 114.2; 78.2; 69.2; 68.7; 65.7; 65.5; 64.7; 64.1; 55.3; 55.2; 49.0; 48.4; 20.8; 20.7; 20.6.

9. Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 5[link]. The carbon-bound H atoms were placed in calculated positions (C—H = 0.93–0.98 Å) and were included in the refinement in the riding model approximation, with Uiso(H) set to 1.2–1.5Ueq(C).

Table 5
Experimental details

Crystal data
Chemical formula C23H24N2O9
Mr 472.44
Crystal system, space group Monoclinic, C2/c
Temperature (K) 293
a, b, c (Å) 23.6396 (5), 8.2906 (2), 24.7683 (5)
β (°) 110.013 (1)
V3) 4561.13 (18)
Z 8
Radiation type Mo Kα
μ (mm−1) 0.11
Crystal size (mm) 0.40 × 0.36 × 0.18
 
Data collection
Diffractometer Enraf–Nonius TurboCAD-4
Absorption correction Multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.])
Tmin, Tmax 0.686, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections 22357, 4172, 3646
Rint 0.020
(sin θ/λ)max−1) 0.603
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.112, 1.01
No. of reflections 4172
No. of parameters 310
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.30, −0.22
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1989[Enraf-Nonius (1989). CAD-4 EXPRESS. Enraf-Nonius, Delft, The Netherlands.]), XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]), SIR2014 (Burla et al., 2015[Burla, M. C., Caliandro, R., Carrozzini, B., Cascarano, G. L., Cuocci, C., Giacovazzo, C., Mallamo, M., Mazzone, A. & Polidori, G. (2015). J. Appl. Cryst. 48, 306-309.]), SHELXL2018/3 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), ORTEP-3 for Windows (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]), MarvinSketch (ChemAxon, 2010[ChemAxon (2010). Marvinsketch. http://www.chemaxon.com.]), DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1989); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR2014 (Burla et al., 2015); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012), MarvinSketch (ChemAxon, 2010) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

4-Nitrobenzyl 3,4-bis(acetyloxy)-2-(4-methoxyphenyl)pyrrolidine-1-carboxylate top
Crystal data top
C23H24N2O9F(000) = 1984
Mr = 472.44Dx = 1.376 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 23.6396 (5) ÅCell parameters from 9984 reflections
b = 8.2906 (2) Åθ = 2.6–25.4°
c = 24.7683 (5) ŵ = 0.11 mm1
β = 110.013 (1)°T = 293 K
V = 4561.13 (18) Å3Irregular, colourless
Z = 80.40 × 0.36 × 0.18 mm
Data collection top
Enraf–Nonius TurboCAD-4
diffractometer
Rint = 0.020
Radiation source: Enraf–Nonius FR590θmax = 25.4°, θmin = 1.8°
non–profiled ω/2θ scansh = 2828
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
k = 710
Tmin = 0.686, Tmax = 0.745l = 2929
22357 measured reflections3 standard reflections every 120 min
4172 independent reflections intensity decay: 2%
3646 reflections with I > 2σ(I)
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.112H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0475P)2 + 5.1476P]
where P = (Fo2 + 2Fc2)/3
4172 reflections(Δ/σ)max = 0.001
310 parametersΔρmax = 0.30 e Å3
0 restraintsΔρmin = 0.22 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.41109 (7)0.33440 (18)0.82213 (6)0.0313 (3)
H10.4397780.2650450.8123980.038*
C20.35064 (7)0.33405 (19)0.77230 (7)0.0336 (4)
H20.3277400.4304570.7749430.040*
C30.31777 (7)0.1856 (2)0.78170 (7)0.0378 (4)
H30.2742730.1920510.7612540.045*
C40.33330 (7)0.1864 (2)0.84615 (7)0.0403 (4)
H4A0.3048090.2511330.8571370.048*
H4B0.3335670.0777800.8607670.048*
C50.43296 (7)0.20974 (18)0.91863 (7)0.0345 (4)
C60.53264 (8)0.2143 (2)0.98048 (8)0.0528 (5)
H6A0.5422520.1031540.9749170.063*
H6B0.5169310.2174411.0118780.063*
C70.58827 (8)0.3154 (2)0.99508 (7)0.0417 (4)
C80.64314 (9)0.2417 (3)1.02204 (9)0.0565 (5)
H80.6447870.1305821.0275010.068*
C90.69526 (9)0.3306 (3)1.04088 (10)0.0645 (6)
H90.7321070.2804461.0589710.077*
C100.69219 (8)0.4939 (3)1.03263 (8)0.0528 (5)
C110.63872 (9)0.5713 (3)1.00515 (9)0.0544 (5)
H110.6375810.6822630.9994500.065*
C120.58661 (8)0.4804 (2)0.98615 (8)0.0494 (5)
H120.5500170.5307220.9671440.059*
C130.43684 (7)0.50197 (18)0.83547 (6)0.0316 (3)
C140.40971 (7)0.6175 (2)0.85901 (7)0.0372 (4)
H140.3764370.5895790.8689270.045*
C150.43136 (8)0.7731 (2)0.86789 (8)0.0412 (4)
H150.4127180.8490670.8837780.049*
C160.48067 (8)0.8167 (2)0.85329 (8)0.0438 (4)
C170.50828 (8)0.7033 (2)0.83008 (9)0.0513 (5)
H170.5415300.7314890.8201580.062*
C180.48621 (8)0.5466 (2)0.82156 (8)0.0430 (4)
H180.5051940.4703340.8061320.052*
C190.54992 (12)1.0247 (3)0.85250 (17)0.1022 (11)
H19A0.5837750.9626890.8757910.153*
H19B0.5570731.1370120.8617930.153*
H19C0.5444791.0084480.8126610.153*
C200.31789 (8)0.3956 (2)0.67329 (7)0.0412 (4)
C210.33733 (10)0.4076 (3)0.62226 (9)0.0641 (6)
H21A0.3410210.3012500.6084720.096*
H21B0.3755140.4614910.6328650.096*
H21C0.3079750.4676270.5925480.096*
C220.31168 (8)0.0347 (2)0.71859 (8)0.0416 (4)
C230.34279 (10)0.1848 (2)0.71099 (9)0.0565 (5)
H23A0.3292840.2738870.7281730.085*
H23B0.3854820.1719360.7291650.085*
H23C0.3336490.2052640.6707510.085*
N10.39393 (6)0.25809 (16)0.86773 (6)0.0352 (3)
N20.74834 (9)0.5888 (3)1.05360 (8)0.0727 (6)
O10.41991 (6)0.12222 (15)0.95189 (5)0.0462 (3)
O20.48803 (5)0.27396 (14)0.92893 (5)0.0394 (3)
O30.79605 (8)0.5171 (3)1.06567 (10)0.1097 (8)
O40.74408 (9)0.7331 (3)1.05857 (8)0.0893 (6)
O50.49776 (7)0.97485 (16)0.86316 (8)0.0654 (4)
O60.36272 (5)0.33834 (15)0.71959 (5)0.0410 (3)
O70.26983 (6)0.4321 (2)0.67504 (6)0.0632 (4)
O80.34399 (5)0.04280 (14)0.76655 (5)0.0441 (3)
O90.26372 (7)0.0104 (2)0.68714 (6)0.0684 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0301 (8)0.0308 (8)0.0299 (8)0.0021 (6)0.0061 (6)0.0014 (6)
C20.0311 (8)0.0356 (8)0.0303 (8)0.0036 (6)0.0057 (6)0.0026 (6)
C30.0270 (8)0.0371 (9)0.0431 (9)0.0004 (6)0.0039 (7)0.0050 (7)
C40.0319 (8)0.0426 (9)0.0435 (9)0.0059 (7)0.0091 (7)0.0002 (7)
C50.0390 (9)0.0266 (7)0.0342 (8)0.0002 (6)0.0075 (7)0.0010 (7)
C60.0460 (10)0.0521 (11)0.0440 (10)0.0034 (9)0.0057 (8)0.0169 (9)
C70.0402 (9)0.0491 (10)0.0295 (8)0.0012 (8)0.0037 (7)0.0018 (7)
C80.0469 (11)0.0589 (12)0.0545 (12)0.0051 (9)0.0055 (9)0.0106 (10)
C90.0381 (10)0.0846 (17)0.0617 (13)0.0065 (10)0.0053 (9)0.0104 (12)
C100.0394 (10)0.0797 (15)0.0384 (10)0.0140 (10)0.0121 (8)0.0139 (10)
C110.0595 (12)0.0502 (11)0.0546 (12)0.0096 (9)0.0207 (10)0.0123 (9)
C120.0407 (10)0.0497 (11)0.0518 (11)0.0012 (8)0.0082 (8)0.0019 (9)
C130.0315 (8)0.0317 (8)0.0264 (7)0.0002 (6)0.0032 (6)0.0023 (6)
C140.0380 (9)0.0376 (9)0.0369 (9)0.0017 (7)0.0140 (7)0.0002 (7)
C150.0452 (10)0.0365 (9)0.0411 (9)0.0006 (7)0.0139 (8)0.0052 (7)
C160.0407 (9)0.0327 (9)0.0521 (11)0.0051 (7)0.0085 (8)0.0015 (8)
C170.0409 (10)0.0440 (10)0.0746 (14)0.0085 (8)0.0269 (10)0.0028 (9)
C180.0395 (9)0.0381 (9)0.0541 (11)0.0003 (7)0.0195 (8)0.0042 (8)
C190.0737 (17)0.0508 (14)0.194 (4)0.0262 (13)0.061 (2)0.0194 (18)
C200.0432 (10)0.0369 (9)0.0345 (9)0.0017 (7)0.0017 (7)0.0005 (7)
C210.0683 (14)0.0829 (16)0.0367 (10)0.0014 (12)0.0123 (10)0.0033 (10)
C220.0423 (10)0.0399 (9)0.0401 (9)0.0079 (7)0.0110 (8)0.0029 (7)
C230.0630 (13)0.0459 (11)0.0595 (13)0.0002 (9)0.0196 (10)0.0112 (9)
N10.0330 (7)0.0341 (7)0.0328 (7)0.0050 (6)0.0042 (6)0.0035 (6)
N20.0582 (12)0.1074 (18)0.0531 (11)0.0282 (12)0.0200 (9)0.0212 (11)
O10.0504 (7)0.0427 (7)0.0422 (7)0.0020 (6)0.0116 (6)0.0132 (6)
O20.0364 (6)0.0372 (6)0.0338 (6)0.0042 (5)0.0019 (5)0.0075 (5)
O30.0421 (10)0.154 (2)0.1255 (18)0.0190 (12)0.0188 (10)0.0200 (15)
O40.0919 (13)0.1010 (15)0.0811 (13)0.0485 (12)0.0372 (11)0.0322 (11)
O50.0564 (8)0.0360 (7)0.1062 (13)0.0139 (6)0.0308 (8)0.0144 (7)
O60.0363 (6)0.0518 (7)0.0304 (6)0.0068 (5)0.0058 (5)0.0001 (5)
O70.0482 (8)0.0815 (11)0.0506 (8)0.0230 (7)0.0050 (6)0.0112 (7)
O80.0352 (6)0.0376 (6)0.0502 (7)0.0009 (5)0.0024 (5)0.0093 (5)
O90.0561 (9)0.0722 (10)0.0559 (9)0.0083 (8)0.0077 (7)0.0200 (8)
Geometric parameters (Å, º) top
C1—N11.468 (2)C12—H120.9300
C1—C131.507 (2)C13—C181.376 (2)
C1—C21.536 (2)C13—C141.388 (2)
C1—H10.9800C14—C151.377 (2)
C2—O61.4293 (19)C14—H140.9300
C2—C31.516 (2)C15—C161.381 (3)
C2—H20.9800C15—H150.9300
C3—O81.444 (2)C16—O51.369 (2)
C3—C41.511 (2)C16—C171.378 (3)
C3—H30.9800C17—C181.388 (3)
C4—N11.472 (2)C17—H170.9300
C4—H4A0.9700C18—H180.9300
C4—H4B0.9700C19—O51.409 (3)
C5—O11.214 (2)C19—H19A0.9600
C5—N11.344 (2)C19—H19B0.9600
C5—O21.3476 (19)C19—H19C0.9600
C6—O21.4371 (19)C20—O71.191 (2)
C6—C71.496 (3)C20—O61.354 (2)
C6—H6A0.9700C20—C211.488 (3)
C6—H6B0.9700C21—H21A0.9600
C7—C81.382 (3)C21—H21B0.9600
C7—C121.385 (3)C21—H21C0.9600
C8—C91.373 (3)C22—O91.195 (2)
C8—H80.9300C22—O81.337 (2)
C9—C101.368 (3)C22—C231.490 (3)
C9—H90.9300C23—H23A0.9600
C10—C111.372 (3)C23—H23B0.9600
C10—N21.476 (3)C23—H23C0.9600
C11—C121.382 (3)N2—O31.218 (3)
C11—H110.9300N2—O41.210 (3)
N1—C1—C13115.20 (13)C18—C13—C1120.44 (15)
N1—C1—C2101.03 (12)C14—C13—C1121.24 (14)
C13—C1—C2111.89 (12)C15—C14—C13120.91 (16)
N1—C1—H1109.5C15—C14—H14119.5
C13—C1—H1109.5C13—C14—H14119.5
C2—C1—H1109.5C14—C15—C16120.28 (16)
O6—C2—C3115.70 (13)C14—C15—H15119.9
O6—C2—C1108.19 (12)C16—C15—H15119.9
C3—C2—C1105.25 (13)O5—C16—C17125.10 (17)
O6—C2—H2109.2O5—C16—C15115.33 (17)
C3—C2—H2109.2C17—C16—C15119.56 (16)
C1—C2—H2109.2C16—C17—C18119.65 (17)
O8—C3—C4107.94 (14)C16—C17—H17120.2
O8—C3—C2109.73 (13)C18—C17—H17120.2
C4—C3—C2101.92 (13)C13—C18—C17121.37 (17)
O8—C3—H3112.2C13—C18—H18119.3
C4—C3—H3112.2C17—C18—H18119.3
C2—C3—H3112.2O5—C19—H19A109.5
N1—C4—C3103.88 (13)O5—C19—H19B109.5
N1—C4—H4A111.0H19A—C19—H19B109.5
C3—C4—H4A111.0O5—C19—H19C109.5
N1—C4—H4B111.0H19A—C19—H19C109.5
C3—C4—H4B111.0H19B—C19—H19C109.5
H4A—C4—H4B109.0O7—C20—O6122.57 (17)
O1—C5—N1124.23 (15)O7—C20—C21126.14 (17)
O1—C5—O2124.12 (15)O6—C20—C21111.29 (16)
N1—C5—O2111.62 (14)C20—C21—H21A109.5
O2—C6—C7109.81 (15)C20—C21—H21B109.5
O2—C6—H6A109.7H21A—C21—H21B109.5
C7—C6—H6A109.7C20—C21—H21C109.5
O2—C6—H6B109.7H21A—C21—H21C109.5
C7—C6—H6B109.7H21B—C21—H21C109.5
H6A—C6—H6B108.2O9—C22—O8123.71 (17)
C8—C7—C12119.00 (18)O9—C22—C23125.35 (17)
C8—C7—C6118.12 (17)O8—C22—C23110.92 (15)
C12—C7—C6122.73 (17)C22—C23—H23A109.5
C9—C8—C7120.8 (2)C22—C23—H23B109.5
C9—C8—H8119.6H23A—C23—H23B109.5
C7—C8—H8119.6C22—C23—H23C109.5
C10—C9—C8119.0 (2)H23A—C23—H23C109.5
C10—C9—H9120.5H23B—C23—H23C109.5
C8—C9—H9120.5C5—N1—C1124.66 (13)
C9—C10—C11121.97 (19)C5—N1—C4119.39 (14)
C9—C10—N2118.7 (2)C1—N1—C4112.69 (12)
C11—C10—N2119.3 (2)O3—N2—O4124.1 (2)
C10—C11—C12118.5 (2)O3—N2—C10118.1 (2)
C10—C11—H11120.8O4—N2—C10117.8 (2)
C12—C11—H11120.8C5—O2—C6113.56 (13)
C11—C12—C7120.73 (18)C16—O5—C19118.13 (17)
C11—C12—H12119.6C20—O6—C2116.07 (13)
C7—C12—H12119.6C22—O8—C3117.36 (13)
C18—C13—C14118.23 (15)
N1—C1—C2—O6155.47 (12)C15—C16—C17—C180.1 (3)
C13—C1—C2—O681.46 (16)C14—C13—C18—C170.7 (3)
N1—C1—C2—C331.22 (15)C1—C13—C18—C17175.80 (16)
C13—C1—C2—C3154.29 (13)C16—C17—C18—C130.5 (3)
O6—C2—C3—O844.85 (17)O1—C5—N1—C1166.43 (16)
C1—C2—C3—O874.51 (15)O2—C5—N1—C115.2 (2)
O6—C2—C3—C4159.06 (13)O1—C5—N1—C48.4 (3)
C1—C2—C3—C439.70 (16)O2—C5—N1—C4173.30 (14)
O8—C3—C4—N183.80 (15)C13—C1—N1—C568.82 (19)
C2—C3—C4—N131.73 (16)C2—C1—N1—C5170.43 (14)
O2—C6—C7—C8148.04 (18)C13—C1—N1—C4131.85 (14)
O2—C6—C7—C1236.3 (3)C2—C1—N1—C411.10 (16)
C12—C7—C8—C91.3 (3)C3—C4—N1—C5147.44 (15)
C6—C7—C8—C9174.4 (2)C3—C4—N1—C113.09 (18)
C7—C8—C9—C100.1 (3)C9—C10—N2—O316.0 (3)
C8—C9—C10—C111.2 (3)C11—C10—N2—O3163.5 (2)
C8—C9—C10—N2179.30 (19)C9—C10—N2—O4162.9 (2)
C9—C10—C11—C120.9 (3)C11—C10—N2—O417.7 (3)
N2—C10—C11—C12179.61 (18)O1—C5—O2—C67.0 (2)
C10—C11—C12—C70.6 (3)N1—C5—O2—C6174.71 (15)
C8—C7—C12—C111.7 (3)C7—C6—O2—C5168.20 (15)
C6—C7—C12—C11173.92 (19)C17—C16—O5—C194.5 (3)
N1—C1—C13—C18137.44 (16)C15—C16—O5—C19176.2 (2)
C2—C1—C13—C18107.93 (17)O7—C20—O6—C24.1 (2)
N1—C1—C13—C1446.17 (19)C21—C20—O6—C2175.16 (15)
C2—C1—C13—C1468.47 (19)C3—C2—O6—C2085.09 (17)
C18—C13—C14—C150.4 (2)C1—C2—O6—C20157.16 (13)
C1—C13—C14—C15176.07 (15)O9—C22—O8—C32.4 (3)
C13—C14—C15—C160.1 (3)C23—C22—O8—C3176.13 (15)
C14—C15—C16—O5179.04 (16)C4—C3—O8—C22141.18 (15)
C14—C15—C16—C170.4 (3)C2—C3—O8—C22108.54 (16)
O5—C16—C17—C18179.27 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4B···O7i0.972.603.129 (2)115
C6—H6A···O1ii0.972.543.250 (2)130
Symmetry codes: (i) x+1/2, y1/2, z+3/2; (ii) x+1, y, z+2.
Summary of short interatomic contacts (Å) in (I)a top
ContactDistanceSymmetry operation
C6—H6A···O1b2.47-x + 1, -y, -z + 2
C4—H4B···O7b2.55-x + 1/2, y - 1/2, -z + 3/2
C4···O73.13-x + 1/2, y + 1/2, -z + 3/2
C5···O53.08x, y - 1, z
O2···O53.02x, y - 1, z
C6—H6B···C152.73-x + 1, -y + 1, -z + 2
C9—H9···C212.75x + 1/2, -y + 1/2, z + 1/2
O4···O42.75-x + 3/2, -y + 3/2, -z + 2
H17···H23B2.35-x + 1, y + 1, -z + 3/2
Notes: (a) The interatomic distances are calculated in Crystal Explorer 17 (Turner et al., 2017) whereby the X—H bond lengths are adjusted to their neutron values. (b) These interactions correspond to the interactions listed in Table 1.
Percentage contributions of interatomic contacts to the Hirshfeld surface for (I) top
ContactPercentage contribution
H···H42.3
H···O/O···H37.3
H···C/C···H14.9
O···O2.1
O···C/C···O1.2
Others2.2
Summary of interaction energies (kJ mol-1) calculated for (I). top
ContactR (Å)EeleEpolEdisErepEtot
Intra-layer region
C4—H4B···O7i +
C4···O7i10.99-17.8-6.1-29.118.3-37.3
C6—H6A···O1ii9.21-23.8-6.9-23.221.7-37.0
C5···O5iii +
O2···O5iii8.29-8.4-2.7-56.329.1-41.8
C9—H9···C21iv14.12-12.7-3.4-20.512.0-26.4
C6—H6B···C15v +
C4—H4A···O4v6.55-18.1-4.5-87.152.8-65.8
C21—H21C···O4vi15.04-2.1-1.0-3.71.5-5.2
Inter-layer region
H17···H23Bvii10.382.9-1.2-16.58.2-7.1
H17···H21Bvii +
H18···H21Bviii6.24-1.1-1.6-52.923.0-34.2
O4···O4ix13.71-16.1-4.4-16.210.8-27.7
C8—H8···O3x12.70-5.4-1.3-10.21.9-14.4
Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 3/2; (ii) -x + 1, -y, -z + 2; (iii) x, y - 1, z; (iv) x + 1/2, -y + 1/2, z + 1/2; (v) -x + 1, -y + 1, -z + 2; (vi) x - 1/2, -y + 3/2, z - 1/2; (vii) -x + 1, y + 1, - z + 3/2; (viii) -x + 1, y, -z + 3/2; (ix) -x + 3/2, -y + 3/2, -z + 2; (x) -x + 3/2, -y + 1/2, -z + 2.
 

Footnotes

Additional correspondence author, e-mail: edwardt@sunway.edu.my.

Funding information

The Brazilian agencies Coordination for the Improvement of Higher Education Personnel, CAPES, Finance Code 001 and the National Council for Scientific and Technological Development (CNPq) are acknowledged for grant Nos. 312210/2019–1, 433957/2018–2 and 406273/2015–4 to IC, for a fellowship 303207/2017–5 to JZS and a scholarship to SDP. Sunway University Sdn Bhd is also thanked for funding (grant No. STR-RCTR-RCCM-001–2019).

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