4-Nitro-N-phthalyl-l-tryptophan

Tilborg, A.; Boittiaux, I.; Norberg, B.; Lambert, D.; Wouters, J.

doi:10.1107/S1600536811029138

organic compounds

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ISSN: 2056-9890

Volume 67| Part 8| August 2011| Page o2116

doi:10.1107/S1600536811029138

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4-Nitro-N-phthalyl-L-tryptophan

Anaelle Tilborg,^a Irving Boittiaux,^b Bernadette Norberg,^a Didier Lambert ^b and Johan Wouters ^a ^*

^aDepartment of Chemistry, University of Namur, 61, Rue de Bruxelles, B-5000 Namur, Belgium, and ^bLouvain Drug Research Institute (LDRI), UCL, 50, Avenue Mounier, B-1200 Woluwe-Saint-Lambert, Belgium
^*Correspondence e-mail: johan.wouters@fundp.ac.be

(Received 1 July 2011; accepted 19 July 2011; online 23 July 2011)

The crystal structure of the title compound [systematic name: (2R)-3-(1H-indol-3-yl)-2-(4-nitro-1,3-dioxoisoindolin-2-yl)propanoic acid], C₁₉H₁₃N₃O₆, an analogue of epigenetic modulator RG108, is constrained by strong hydrogen bonds between the indole N—H group and a carbonyl O atom of the phthalimide ring of a symmetry-related molecule, and between the protonated O atom of the carboxyl group and a carbonyl O atom of the phthalimide ring. π–π stacking interactions with centroid–centroid distances of 3.638 (1) and 3.610 (1) Å are also observed between indole and phthalimide rings.

Related literature

For crystallographic information and details of the RG108 analogue, see: Braun et al. (2010 ) and for details of the biological evaluation, see: Brueckner et al. (2005 ).

Experimental

Crystal data

C₁₉H₁₃N₃O₆
M_r = 379.33
Monoclinic, P 2₁
a = 7.0569 (3) Å
b = 15.5302 (8) Å
c = 7.6947 (4) Å
β = 95.415 (4)°
V = 839.54 (7) Å³
Z = 2
Cu Kα radiation
μ = 0.97 mm⁻¹
T = 293 K
0.22 × 0.10 × 0.03 mm

Data collection

Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England.]$ ) T_min = 0.815, T_max = 0.972
9007 measured reflections
2966 independent reflections
2735 reflections with I > 2σ(I)
R_int = 0.029

Refinement

R[F² > 2σ(F²)] = 0.031
wR(F²) = 0.091
S = 1.06
2966 reflections
262 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.15 e Å⁻³
Δρ_min = −0.13 e Å⁻³
Absolute structure: Flack (1983 ), 1371 Friedel pairs
Flack parameter: −0.1 (2)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O1ⁱ	0.86 (4)	2.28 (4)	3.002 (3)	142 (4)
O4—H1⋯O2ⁱⁱ	1.00 (4)	1.78 (4)	2.716 (2)	154 (3)
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z]$ ; (ii) x, y, z-1.

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEPIII (Burnett & Johnson, 1996 ) and PLATON (Spek, 2009 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811029138/vm2109sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811029138/vm2109Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811029138/vm2109Isup3.cml

checkCIF report

Comment top

4-Nitro-N-phthalyl-L-tryptophan is an analog of RG108, a DNA methyltransferase (DNMT) inhibitor discovered by virtual screening (Brueckner et al. (2005)). Introduction of a nitro functional group on the phtalimide moiety is excepted to improve inhibition ability (unpublished results).

Isomer S (C9) of 4-nitro-N-phthalyl-tryptophan is obtained from L-tryptophan and nitrophthalic anhydride in DMF.

Two main types of H-bonding interactions are observed in the structure: one between N—H of the indole ring (N2) and O1 of the phtalimide ring, and the other between the protonated oxygen (O4) from the carboxylic moiety and O2 from the phtalimide ring (see Table 1).

In addition to H-bonds, crystal packing organization is further stabilized by π–π-stacking interactions involving symmetry-related molecules, in particularly between the 6-membered coupled rings of nitrophthalimide and indole moiety (see Table 2). No interactions of this type are present in the packing of the dicyclohexylamine salt of RG108 (Braun et al. (2010), because of the presence of the ammonium counter-cation and water molecules included in the crystalline network.

In contrast to the structure of the dicyclohexylamine salt of RG108 (Braun et al. (2010)), where the compound conformation is constrained by strong (charge-assisted) H-bonds with the dicyclohexylammonium ion and extra water molecules, the angle between the two fused rings is 14.23 (4)° in the present structure compared to 58.35 (4)° in the case of the RG108 salt. The torsion angle of the chain between the two aromatic moieties (N1—C9—C10—C11) is also distinct: -155.66 (17)° and -61.93 (17) ° for the title and RG108 salt structures, respectively.

Related literature top

For crystallographic information and details about the RG108 analogue, see: Braun et al. (2010) and for its biological evaluation, see: Brueckner et al. (2005).

Experimental top

Synthesis of the compound was accomplished by micro-wave heating of L-tryptophan (1 mmol, 204 mg) and 4-nitro phthalic anhydride (1 mmol, 193 mg) in 5 ml of DMF. The mixture was then poured in cold aqueous buffer solution (pH = 2) and extracted with ethyl acetate. After drying with Na₂SO₄, the organic phase is evaporated and the residue is purified by flash chromatography (dichloromethane and methanol: 9/1; yield = 60%, 230 mg).

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. ORTEP view and atom numbering of the title compound. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.

(2R)-3-(1H-indol-3-yl)-2-(4-nitro-1,3-dioxoisoindolin- 2-yl)propanoic acid top

Crystal data top

C₁₉H₁₃N₃O₆	F(000) = 392
M_r = 379.33	D_x = 1.501 Mg m⁻³
Monoclinic, P2₁	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2yb	Cell parameters from 4268 reflections
a = 7.0569 (3) Å	θ = 2.8–67.9°
b = 15.5302 (8) Å	µ = 0.97 mm⁻¹
c = 7.6947 (4) Å	T = 293 K
β = 95.415 (4)°	Prism, yellow
V = 839.54 (7) Å³	0.22 × 0.10 × 0.03 mm
Z = 2

Data collection top

Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer	2966 independent reflections
Radiation source: fine-focus sealed tube	2735 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.029
Detector resolution: 10.3712 pixels mm^-1	θ_max = 68.0°, θ_min = 5.7°
ω scans	h = −8→8
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)	k = −18→17
T_min = 0.815, T_max = 0.972	l = −9→8
9007 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.031	w = 1/[σ²(F_o²) + (0.0492P)² + 0.1477P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.091	(Δ/σ)_max < 0.001
S = 1.06	Δρ_max = 0.15 e Å⁻³
2966 reflections	Δρ_min = −0.13 e Å⁻³
262 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.0080 (8)
0 constraints	Absolute structure: Flack (1983), 1371 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.1 (2)
Secondary atom site location: difference Fourier map

Crystal data top

C₁₉H₁₃N₃O₆	V = 839.54 (7) Å³
M_r = 379.33	Z = 2
Monoclinic, P2₁	Cu Kα radiation
a = 7.0569 (3) Å	µ = 0.97 mm⁻¹
b = 15.5302 (8) Å	T = 293 K
c = 7.6947 (4) Å	0.22 × 0.10 × 0.03 mm
β = 95.415 (4)°

Data collection top

Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer	2966 independent reflections
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)	2735 reflections with I > 2σ(I)
T_min = 0.815, T_max = 0.972	R_int = 0.029
9007 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.031	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.091	Δρ_max = 0.15 e Å⁻³
S = 1.06	Δρ_min = −0.13 e Å⁻³
2966 reflections	Absolute structure: Flack (1983), 1371 Friedel pairs
262 parameters	Absolute structure parameter: −0.1 (2)
1 restraint

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.

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

	x	y	z	U_iso*/U_eq
C1	0.7937 (3)	0.58969 (13)	0.3293 (3)	0.0401 (4)
C2	0.8237 (3)	0.64858 (13)	0.4829 (3)	0.0385 (4)
C3	0.7949 (3)	0.73572 (14)	0.5072 (3)	0.0427 (5)
C4	0.8157 (3)	0.77052 (15)	0.6745 (3)	0.0481 (5)
H4	0.7881	0.8283	0.6913	0.058*
C5	0.8772 (3)	0.71950 (17)	0.8159 (3)	0.0533 (6)
H5	0.8943	0.7437	0.9269	0.064*
C6	0.9135 (3)	0.63265 (16)	0.7939 (3)	0.0497 (5)
H6	0.9581	0.5984	0.8881	0.060*
C7	0.8815 (3)	0.59866 (14)	0.6286 (3)	0.0410 (4)
C8	0.8976 (3)	0.50848 (14)	0.5709 (2)	0.0402 (4)
C9	0.8329 (3)	0.42945 (12)	0.2879 (3)	0.0391 (4)
H9	0.9070	0.3854	0.3557	0.047*
C10	0.6282 (3)	0.39570 (14)	0.2619 (3)	0.0479 (5)
H10A	0.5655	0.4077	0.3661	0.057*
H10B	0.5601	0.4265	0.1656	0.057*
C11	0.6167 (3)	0.30101 (14)	0.2249 (3)	0.0437 (5)
C12	0.5649 (3)	0.26268 (17)	0.0691 (3)	0.0532 (6)
H12	0.5355	0.2917	−0.0357	0.064*
C13	0.6095 (3)	0.15405 (15)	0.2600 (3)	0.0488 (5)
C14	0.6192 (3)	0.07499 (16)	0.3441 (4)	0.0607 (7)
H14	0.5920	0.0241	0.2830	0.073*
C15	0.6705 (3)	0.07453 (17)	0.5213 (4)	0.0650 (7)
H15	0.6779	0.0224	0.5810	0.078*
C16	0.7115 (3)	0.15063 (19)	0.6124 (4)	0.0590 (6)
H16	0.7468	0.1482	0.7318	0.071*
C17	0.7012 (3)	0.22977 (16)	0.5303 (3)	0.0479 (5)
H17	0.7294	0.2801	0.5928	0.058*
C18	0.6472 (3)	0.23231 (14)	0.3505 (3)	0.0413 (4)
C19	0.9328 (3)	0.44380 (13)	0.1227 (3)	0.0433 (5)
N1	0.8488 (2)	0.50773 (11)	0.3922 (2)	0.0397 (4)
N2	0.5622 (3)	0.17470 (15)	0.0885 (3)	0.0591 (6)
N3	0.7496 (3)	0.79406 (12)	0.3599 (3)	0.0518 (5)
O1	0.7311 (2)	0.60263 (10)	0.18047 (19)	0.0526 (4)
O2	0.9409 (2)	0.44385 (10)	0.65541 (19)	0.0518 (4)
O3	1.0857 (3)	0.47711 (14)	0.1246 (2)	0.0659 (5)
O4	0.8377 (3)	0.41420 (14)	−0.0186 (2)	0.0709 (6)
O5	0.8221 (3)	0.77922 (12)	0.2254 (2)	0.0683 (5)
O6	0.6475 (3)	0.85593 (12)	0.3807 (3)	0.0768 (6)
H1	0.913 (5)	0.425 (2)	−0.120 (5)	0.093 (11)*
H2	0.525 (6)	0.138 (3)	0.008 (5)	0.095 (12)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0449 (10)	0.0354 (11)	0.0400 (11)	0.0023 (8)	0.0046 (8)	0.0025 (8)
C2	0.0382 (9)	0.0391 (11)	0.0391 (10)	−0.0004 (8)	0.0080 (8)	−0.0029 (8)
C3	0.0408 (10)	0.0409 (11)	0.0475 (11)	−0.0011 (8)	0.0092 (8)	−0.0035 (9)
C4	0.0440 (11)	0.0449 (12)	0.0576 (13)	−0.0067 (9)	0.0161 (9)	−0.0150 (10)
C5	0.0539 (12)	0.0625 (14)	0.0451 (12)	−0.0119 (11)	0.0133 (10)	−0.0138 (11)
C6	0.0527 (12)	0.0579 (15)	0.0397 (11)	−0.0068 (10)	0.0100 (9)	−0.0027 (10)
C7	0.0434 (10)	0.0442 (11)	0.0363 (10)	−0.0038 (8)	0.0083 (8)	−0.0055 (8)
C8	0.0414 (10)	0.0436 (11)	0.0362 (10)	0.0003 (8)	0.0078 (8)	0.0037 (9)
C9	0.0482 (10)	0.0314 (10)	0.0381 (10)	0.0020 (8)	0.0068 (8)	0.0011 (8)
C10	0.0477 (12)	0.0417 (12)	0.0549 (13)	0.0001 (9)	0.0085 (9)	0.0007 (10)
C11	0.0409 (10)	0.0400 (11)	0.0511 (12)	−0.0037 (8)	0.0087 (9)	−0.0006 (9)
C12	0.0575 (13)	0.0598 (15)	0.0422 (11)	−0.0117 (11)	0.0034 (10)	−0.0017 (10)
C13	0.0442 (11)	0.0413 (11)	0.0618 (14)	−0.0044 (9)	0.0104 (10)	−0.0042 (10)
C14	0.0490 (12)	0.0396 (12)	0.095 (2)	−0.0061 (9)	0.0157 (13)	−0.0023 (12)
C15	0.0497 (12)	0.0517 (15)	0.095 (2)	0.0012 (11)	0.0143 (13)	0.0218 (14)
C16	0.0486 (12)	0.0678 (16)	0.0610 (15)	0.0017 (11)	0.0068 (10)	0.0146 (12)
C17	0.0430 (10)	0.0505 (12)	0.0506 (12)	0.0002 (9)	0.0060 (9)	0.0034 (10)
C18	0.0371 (9)	0.0404 (11)	0.0474 (11)	−0.0035 (8)	0.0088 (8)	−0.0003 (9)
C19	0.0553 (12)	0.0359 (10)	0.0388 (10)	−0.0026 (9)	0.0053 (9)	−0.0012 (8)
N1	0.0527 (10)	0.0349 (9)	0.0315 (8)	0.0015 (7)	0.0053 (7)	−0.0001 (7)
N2	0.0653 (13)	0.0558 (14)	0.0568 (13)	−0.0161 (10)	0.0081 (10)	−0.0152 (10)
N3	0.0536 (10)	0.0382 (10)	0.0639 (13)	−0.0008 (8)	0.0069 (9)	−0.0001 (8)
O1	0.0717 (10)	0.0440 (8)	0.0401 (8)	0.0082 (7)	−0.0046 (7)	−0.0003 (7)
O2	0.0694 (10)	0.0456 (9)	0.0406 (8)	0.0043 (7)	0.0057 (7)	0.0065 (7)
O3	0.0628 (11)	0.0857 (13)	0.0511 (9)	−0.0194 (9)	0.0148 (8)	−0.0044 (8)
O4	0.0945 (13)	0.0828 (13)	0.0363 (8)	−0.0362 (11)	0.0113 (9)	−0.0052 (8)
O5	0.1017 (14)	0.0533 (10)	0.0511 (10)	0.0083 (9)	0.0135 (9)	0.0002 (8)
O6	0.0812 (12)	0.0447 (10)	0.1084 (16)	0.0170 (9)	0.0289 (11)	0.0126 (10)

Geometric parameters (Å, º) top

C1—O1	1.205 (3)	C10—H10B	0.9700
C1—N1	1.403 (3)	C11—C12	1.358 (3)
C1—C2	1.493 (3)	C11—C18	1.442 (3)
C2—C3	1.384 (3)	C12—N2	1.375 (3)
C2—C7	1.392 (3)	C12—H12	0.9300
C3—C4	1.391 (3)	C13—N2	1.369 (3)
C3—N3	1.463 (3)	C13—C14	1.386 (4)
C4—C5	1.382 (4)	C13—C18	1.413 (3)
C4—H4	0.9300	C14—C15	1.377 (4)
C5—C6	1.386 (4)	C14—H14	0.9300
C5—H5	0.9300	C15—C16	1.391 (4)
C6—C7	1.376 (3)	C15—H15	0.9300
C6—H6	0.9300	C16—C17	1.381 (4)
C7—C8	1.477 (3)	C16—H16	0.9300
C8—O2	1.219 (2)	C17—C18	1.401 (3)
C8—N1	1.386 (3)	C17—H17	0.9300
C9—N1	1.455 (2)	C19—O3	1.195 (3)
C9—C19	1.527 (3)	C19—O4	1.306 (3)
C9—C10	1.532 (3)	N2—H2	0.86 (4)
C9—H9	0.9800	N3—O5	1.219 (3)
C10—C11	1.499 (3)	N3—O6	1.221 (3)
C10—H10A	0.9700	O4—H1	1.00 (4)

O1—C1—N1	122.92 (18)	C12—C11—C10	127.1 (2)
O1—C1—C2	131.44 (18)	C18—C11—C10	126.7 (2)
N1—C1—C2	105.61 (16)	C11—C12—N2	110.2 (2)
C3—C2—C7	118.11 (19)	C11—C12—H12	124.9
C3—C2—C1	133.98 (19)	N2—C12—H12	124.9
C7—C2—C1	107.76 (18)	N2—C13—C14	130.9 (2)
C2—C3—C4	120.1 (2)	N2—C13—C18	106.9 (2)
C2—C3—N3	121.67 (19)	C14—C13—C18	122.2 (2)
C4—C3—N3	118.2 (2)	C15—C14—C13	117.6 (2)
C5—C4—C3	120.2 (2)	C15—C14—H14	121.2
C5—C4—H4	119.9	C13—C14—H14	121.2
C3—C4—H4	119.9	C14—C15—C16	121.2 (2)
C4—C5—C6	120.6 (2)	C14—C15—H15	119.4
C4—C5—H5	119.7	C16—C15—H15	119.4
C6—C5—H5	119.7	C17—C16—C15	121.8 (2)
C7—C6—C5	118.1 (2)	C17—C16—H16	119.1
C7—C6—H6	121.0	C15—C16—H16	119.1
C5—C6—H6	121.0	C16—C17—C18	118.3 (2)
C6—C7—C2	122.7 (2)	C16—C17—H17	120.8
C6—C7—C8	129.2 (2)	C18—C17—H17	120.8
C2—C7—C8	108.11 (17)	C17—C18—C13	118.9 (2)
O2—C8—N1	123.29 (19)	C17—C18—C11	133.8 (2)
O2—C8—C7	129.99 (18)	C13—C18—C11	107.29 (19)
N1—C8—C7	106.71 (17)	O3—C19—O4	123.7 (2)
N1—C9—C19	108.63 (16)	O3—C19—C9	122.70 (19)
N1—C9—C10	112.37 (17)	O4—C19—C9	113.59 (18)
C19—C9—C10	116.40 (17)	C8—N1—C1	111.65 (16)
N1—C9—H9	106.3	C8—N1—C9	123.58 (16)
C19—C9—H9	106.3	C1—N1—C9	124.30 (16)
C10—C9—H9	106.3	C13—N2—C12	109.5 (2)
C11—C10—C9	113.22 (18)	C13—N2—H2	125 (3)
C11—C10—H10A	108.9	C12—N2—H2	125 (3)
C9—C10—H10A	108.9	O5—N3—O6	124.1 (2)
C11—C10—H10B	108.9	O5—N3—C3	117.55 (18)
C9—C10—H10B	108.9	O6—N3—C3	118.3 (2)
H10A—C10—H10B	107.7	C19—O4—H1	109 (2)
C12—C11—C18	106.1 (2)

O1—C1—C2—C3	−1.5 (4)	C16—C17—C18—C13	−1.3 (3)
N1—C1—C2—C3	−179.2 (2)	C16—C17—C18—C11	178.1 (2)
O1—C1—C2—C7	173.8 (2)	N2—C13—C18—C17	−179.45 (18)
N1—C1—C2—C7	−3.9 (2)	C14—C13—C18—C17	1.8 (3)
C7—C2—C3—C4	−2.8 (3)	N2—C13—C18—C11	1.0 (2)
C1—C2—C3—C4	172.1 (2)	C14—C13—C18—C11	−177.7 (2)
C7—C2—C3—N3	174.80 (18)	C12—C11—C18—C17	−179.8 (2)
C1—C2—C3—N3	−10.3 (3)	C10—C11—C18—C17	−3.3 (4)
C2—C3—C4—C5	4.2 (3)	C12—C11—C18—C13	−0.4 (2)
N3—C3—C4—C5	−173.46 (19)	C10—C11—C18—C13	176.2 (2)
C3—C4—C5—C6	−1.9 (3)	N1—C9—C19—O3	45.1 (3)
C4—C5—C6—C7	−1.7 (3)	C10—C9—C19—O3	173.1 (2)
C5—C6—C7—C2	3.2 (3)	N1—C9—C19—O4	−136.7 (2)
C5—C6—C7—C8	−176.1 (2)	C10—C9—C19—O4	−8.7 (3)
C3—C2—C7—C6	−0.9 (3)	O2—C8—N1—C1	176.27 (19)
C1—C2—C7—C6	−177.10 (18)	C7—C8—N1—C1	−2.7 (2)
C3—C2—C7—C8	178.52 (17)	O2—C8—N1—C9	3.8 (3)
C1—C2—C7—C8	2.4 (2)	C7—C8—N1—C9	−175.13 (18)
C6—C7—C8—O2	0.6 (4)	O1—C1—N1—C8	−173.90 (19)
C2—C7—C8—O2	−178.8 (2)	C2—C1—N1—C8	4.1 (2)
C6—C7—C8—N1	179.5 (2)	O1—C1—N1—C9	−1.5 (3)
C2—C7—C8—N1	0.1 (2)	C2—C1—N1—C9	176.45 (17)
N1—C9—C10—C11	−155.69 (18)	C19—C9—N1—C8	−134.89 (18)
C19—C9—C10—C11	78.1 (2)	C10—C9—N1—C8	94.9 (2)
C9—C10—C11—C12	−105.8 (3)	C19—C9—N1—C1	53.6 (2)
C9—C10—C11—C18	78.3 (3)	C10—C9—N1—C1	−76.7 (2)
C18—C11—C12—N2	−0.4 (3)	C14—C13—N2—C12	177.3 (2)
C10—C11—C12—N2	−176.9 (2)	C18—C13—N2—C12	−1.3 (3)
N2—C13—C14—C15	−179.5 (2)	C11—C12—N2—C13	1.1 (3)
C18—C13—C14—C15	−1.1 (3)	C2—C3—N3—O5	−34.6 (3)
C13—C14—C15—C16	−0.1 (4)	C4—C3—N3—O5	143.1 (2)
C14—C15—C16—C17	0.5 (4)	C2—C3—N3—O6	147.9 (2)
C15—C16—C17—C18	0.2 (3)	C4—C3—N3—O6	−34.5 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1ⁱ	0.86 (4)	2.28 (4)	3.002 (3)	142 (4)
O4—H1···O2ⁱⁱ	1.00 (4)	1.78 (4)	2.716 (2)	154 (3)

Symmetry codes: (i) −x+1, y−1/2, −z; (ii) x, y, z−1.

Experimental details

Crystal data
Chemical formula	C₁₉H₁₃N₃O₆
M_r	379.33
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	293
a, b, c (Å)	7.0569 (3), 15.5302 (8), 7.6947 (4)
β (°)	95.415 (4)
V (Å³)	839.54 (7)
Z	2
Radiation type	Cu Kα
µ (mm⁻¹)	0.97
Crystal size (mm)	0.22 × 0.10 × 0.03

Data collection
Diffractometer	Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer
Absorption correction	Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)
T_min, T_max	0.815, 0.972
No. of measured, independent and observed [I > 2σ(I)] reflections	9007, 2966, 2735
R_int	0.029
(sin θ/λ)_max (Å⁻¹)	0.601

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.091, 1.06
No. of reflections	2966
No. of parameters	262
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.15, −0.13
Absolute structure	Flack (1983), 1371 Friedel pairs
Absolute structure parameter	−0.1 (2)

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 2008), ORTEPIII (Burnett & Johnson, 1996) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1ⁱ	0.86 (4)	2.28 (4)	3.002 (3)	142 (4)
O4—H1···O2ⁱⁱ	1.00 (4)	1.78 (4)	2.716 (2)	154 (3)

Symmetry codes: (i) −x+1, y−1/2, −z; (ii) x, y, z−1.

π–π stacking interactions between six-membered rings from indole (C13—C18; ring centroid Cg(1)) and nitrophthalimide (C2—C7; ring centroid Cg(2)). top

Cg-Cg : distance (Å) between ring centroids; α : dihedral angle(°) between ring planes 1 and 2 ; β : angle (°) between Cg(1)-->Cg(2) vector and normal to ring plane 1 ; γ : angle (°) between Cg(1)-->Cg(2) vector and normal to ring plane 2 ; Cg1_Perp : perpendicular distance (Å) of Cg(1) on ring plane 2 ; Cg2_Perp : perpendicular distance (Å) of Cg(2) on ring plane 1.

Cg(I)-Cg(J)	sym (J)	Cg-Cg	α	β	γ	Cg1_Perp	Cg2_Perp
Cg(1)-Cg(2)	(i)	3.638 (1)	7.24	18.69	20.72	-3.403 (1)	3.446 (1)
Cg(1)-Cg(2)	(ii)	3.610 (1)	7.24	19.41	12.26	3.528 (1)	3.405 (1)

Symmetry codes : (i) 1 - x, 1/2 + y, 1 - z, (ii) 2 - x, 1/2 + y, 1 - z

Acknowledgements

This work was supported in part by the Fonds National de la Recherche Scientifique (FRS – FNRS, Belgium) by a Télévie grant (IB). AT acknowledges the FRIA (Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture) for financial support.

References

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