organic compounds
5-Methoxy-1-[(5-methoxy-1H-indol-2-yl)methyl]-1H-indole
aDepartment of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia, and bX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
*Correspondence e-mail: hkfun@usm.my
In the title compound, C19H18N2O2, the two indole ring systems are essentially planar [maximum deviation = 0.015 (2) Å in both indole ring systems] and make a dihedral angle of 72.17 (7)° with each other. In the crystal, the molecules are linked into a zigzag chain along the a axis via N—H⋯O hydrogen bonds.
Related literature
For the biological activity of melatonin (MLT), see: Csernus & Mess (2003); Nosjean et al. (2000); Blask et al. (2002); Genovese et al. (2005); Mills et al. (2005); Peres (2005); Sofic et al. (2005); Witt-Enderby et al. (2006). For related structures, see: Narayanan et al. (2011); Deng et al. (2011). For the synthesis, see: Attia et al. (2008).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
10.1107/S1600536812009257/is5084sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812009257/is5084Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536812009257/is5084Isup3.cml
(5-Methoxy-1H-indol-1-yl)(5-methoxy-1H-indol-2-yl)methanone (0.50 g, 156.03 mmol) was dissolved in dry THF (5 ml) and was added drop-wise to a cooled (0 °C) suspension of LiAlH4/AlCl3 in dry diethyl ether (prepared by a slow addition of AlCl3 (0.32 g, 2.41 mmol) to a suspension LiAlH4 (0.27 g, 7.13 mmol) in dry diethyl ether (15 ml) at 0 °C). The resulting reaction mixture was stirred at 0 °C for one hour and at room temperature for another one hour. The reaction was quenched by a slow addition of saturated sodium sulfate solution. The solids formed were removed by filtration, washed with chloroform (20 ml) and the combined organic phase was dried (Na2SO4) and evaporated under reduced pressure. The residue was purified by silica gel
(chloroform/methanol/ammonia, 10.0:1.0:0.1) to produce the title compound as a light red powder which was recrystallized from ethanol to give single crystals (m.p. 173–174 °C).N-bound H atom was located in a difference Fourier map and refined freely [N—H = 0.88 (2) Å]. Other H atoms were positioned geometrically (C—H = 0.93–0.97 Å) and refined using a riding model, with Uiso(H) = 1.2 or 1.5Ueq(C). A rotating group model was applied to the methyl groups.
Melatonin (N-acetyl-5-methoxytryptamine, MLT) is primarily produced by the pineal gland in the brain with a marked circadian rhythm normally peaking in the dark to regulate sleep. MLT acts through activation of two G-protein-coupled receptors, designated as MT1 and MT2 (Csernus & Mess, 2003). In addition, a low-affinity putative MLT binding site called MT3 has been recently characterized as a melatonin-sensitive form of the human enzyme quinine reductase 2 (Nosjean et al., 2000). MLT has found widespread use in the treatment of sleep disorders. Other effects described in the literature include its anti-inflammatory, pain modulatory, antitumor, and antioxidant properties (Blask et al., 2002; Genovese et al., 2005; Mills et al., 2005; Peres, 2005; Sofic et al., 2005; Witt-Enderby et al., 2006). The title compound is an intermediate which could yield, via the reported procedure (Attia et al., 2008), various MLT analogues which can be evaluated for their potency and selectivity for MLT receptor subtypes.
In the title compound (Fig. 1), the indole ring systems (N1/C10–C17 & N2/C1–C8) are essentially planar with maximum deviations of 0.015 (2) Å at atom C10 and C2, respectively. In addition, the indole ring systems are almost perpendicular to each other with dihedral angle of 72.17 (7)°. Bond lengths and angles are within the normal range and are comparable to those in the related structures (Narayanan et al., 2011; Deng et al., 2011).
The
is shown in Fig. 2. The molecules are linked into one dimensional zigzag chains along a-axis via N2—H1N2···O1 interactions (Table 1).For the biological activity of melatonin (MLT), see: Csernus & Mess (2003); Nosjean et al. (2000); Blask et al. (2002); Genovese et al. (2005); Mills et al. (2005); Peres (2005); Sofic et al. (2005); Witt-Enderby et al. (2006). For related structures, see: Narayanan et al. (2011); Deng et al. (2011). For the synthesis, see: Attia et al. (2008).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C19H18N2O2 | F(000) = 648 |
Mr = 306.35 | Dx = 1.286 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: -P 2ybc | Cell parameters from 919 reflections |
a = 9.4446 (5) Å | θ = 4.5–60.8° |
b = 19.5625 (8) Å | µ = 0.68 mm−1 |
c = 8.6657 (5) Å | T = 296 K |
β = 98.903 (4)° | Plate, pink |
V = 1581.78 (14) Å3 | 0.92 × 0.20 × 0.06 mm |
Z = 4 |
Bruker APEXII CCD diffractometer | 2584 independent reflections |
Radiation source: fine-focus sealed tube | 2087 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.041 |
φ and ω scans | θmax = 65.0°, θmin = 4.5° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −11→11 |
Tmin = 0.575, Tmax = 0.961 | k = −22→22 |
9421 measured reflections | l = −8→9 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.046 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.133 | w = 1/[σ2(Fo2) + (0.0478P)2 + 0.3465P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
2584 reflections | Δρmax = 0.15 e Å−3 |
215 parameters | Δρmin = −0.14 e Å−3 |
0 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0029 (5) |
C19H18N2O2 | V = 1581.78 (14) Å3 |
Mr = 306.35 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 9.4446 (5) Å | µ = 0.68 mm−1 |
b = 19.5625 (8) Å | T = 296 K |
c = 8.6657 (5) Å | 0.92 × 0.20 × 0.06 mm |
β = 98.903 (4)° |
Bruker APEXII CCD diffractometer | 2584 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 2087 reflections with I > 2σ(I) |
Tmin = 0.575, Tmax = 0.961 | Rint = 0.041 |
9421 measured reflections |
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.133 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 0.15 e Å−3 |
2584 reflections | Δρmin = −0.14 e Å−3 |
215 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.57956 (17) | 0.66569 (8) | 0.6878 (2) | 0.0604 (4) | |
N2 | 0.32036 (18) | 0.76234 (9) | 0.5805 (2) | 0.0588 (4) | |
O1 | 1.08253 (15) | 0.66541 (8) | 0.44352 (19) | 0.0727 (5) | |
O2 | 0.1802 (2) | 1.02435 (9) | 0.3902 (2) | 0.0978 (6) | |
C1 | 0.4392 (2) | 0.77296 (11) | 0.6916 (2) | 0.0573 (5) | |
C2 | 0.4672 (2) | 0.84059 (11) | 0.7021 (2) | 0.0616 (5) | |
H2A | 0.5421 | 0.8610 | 0.7683 | 0.074* | |
C3 | 0.36179 (19) | 0.87542 (10) | 0.5938 (2) | 0.0536 (5) | |
C4 | 0.3345 (2) | 0.94428 (11) | 0.5531 (3) | 0.0644 (6) | |
H4A | 0.3924 | 0.9789 | 0.6018 | 0.077* | |
C5 | 0.2203 (2) | 0.95918 (11) | 0.4396 (3) | 0.0675 (6) | |
C6 | 0.1345 (2) | 0.90736 (12) | 0.3641 (3) | 0.0703 (6) | |
H6A | 0.0593 | 0.9188 | 0.2859 | 0.084* | |
C7 | 0.1585 (2) | 0.84013 (12) | 0.4025 (3) | 0.0661 (6) | |
H7A | 0.1008 | 0.8059 | 0.3519 | 0.079* | |
C8 | 0.27154 (19) | 0.82467 (9) | 0.5191 (2) | 0.0529 (5) | |
C9 | 0.5147 (2) | 0.71548 (12) | 0.7821 (3) | 0.0709 (6) | |
H9A | 0.5893 | 0.7342 | 0.8602 | 0.085* | |
H9B | 0.4470 | 0.6918 | 0.8368 | 0.085* | |
C10 | 0.5303 (2) | 0.60163 (11) | 0.6481 (3) | 0.0728 (6) | |
H10A | 0.4461 | 0.5831 | 0.6732 | 0.087* | |
C11 | 0.6216 (2) | 0.56865 (11) | 0.5667 (3) | 0.0704 (6) | |
H11A | 0.6112 | 0.5244 | 0.5271 | 0.084* | |
C12 | 0.73578 (19) | 0.61433 (9) | 0.5536 (2) | 0.0535 (5) | |
C13 | 0.86132 (19) | 0.60976 (9) | 0.4852 (2) | 0.0552 (5) | |
H13A | 0.8813 | 0.5708 | 0.4311 | 0.066* | |
C14 | 0.95290 (19) | 0.66412 (10) | 0.5005 (2) | 0.0538 (5) | |
C15 | 0.9232 (2) | 0.72402 (10) | 0.5783 (2) | 0.0565 (5) | |
H15A | 0.9874 | 0.7603 | 0.5852 | 0.068* | |
C16 | 0.8003 (2) | 0.72991 (9) | 0.6444 (2) | 0.0548 (5) | |
H16A | 0.7802 | 0.7696 | 0.6961 | 0.066* | |
C17 | 0.70772 (19) | 0.67448 (9) | 0.6312 (2) | 0.0505 (4) | |
C18 | 1.1240 (3) | 0.60545 (15) | 0.3717 (4) | 0.0934 (8) | |
H18A | 1.2164 | 0.6122 | 0.3411 | 0.140* | |
H18B | 1.0550 | 0.5953 | 0.2811 | 0.140* | |
H18C | 1.1287 | 0.5680 | 0.4440 | 0.140* | |
C19 | 0.2324 (3) | 1.07922 (13) | 0.4857 (4) | 0.1022 (9) | |
H19A | 0.1819 | 1.1201 | 0.4492 | 0.153* | |
H19C | 0.3328 | 1.0851 | 0.4823 | 0.153* | |
H19D | 0.2184 | 1.0701 | 0.5911 | 0.153* | |
H1N2 | 0.274 (3) | 0.7238 (12) | 0.559 (3) | 0.072 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0524 (9) | 0.0644 (10) | 0.0664 (11) | 0.0041 (7) | 0.0159 (7) | 0.0093 (8) |
N2 | 0.0544 (9) | 0.0598 (10) | 0.0637 (11) | −0.0052 (8) | 0.0135 (7) | 0.0005 (8) |
O1 | 0.0617 (8) | 0.0756 (10) | 0.0863 (11) | −0.0066 (7) | 0.0287 (7) | −0.0043 (8) |
O2 | 0.1246 (15) | 0.0672 (10) | 0.0933 (14) | 0.0037 (9) | −0.0091 (11) | 0.0129 (9) |
C1 | 0.0501 (10) | 0.0742 (13) | 0.0501 (12) | 0.0041 (9) | 0.0153 (8) | −0.0015 (9) |
C2 | 0.0528 (11) | 0.0777 (14) | 0.0531 (12) | −0.0001 (9) | 0.0040 (8) | −0.0115 (9) |
C3 | 0.0514 (10) | 0.0635 (11) | 0.0475 (11) | −0.0020 (8) | 0.0132 (8) | −0.0084 (8) |
C4 | 0.0669 (12) | 0.0638 (13) | 0.0615 (13) | −0.0084 (10) | 0.0073 (10) | −0.0102 (9) |
C5 | 0.0758 (13) | 0.0634 (12) | 0.0624 (14) | 0.0007 (10) | 0.0078 (10) | 0.0034 (10) |
C6 | 0.0682 (13) | 0.0769 (14) | 0.0617 (14) | −0.0004 (11) | −0.0031 (10) | 0.0038 (10) |
C7 | 0.0601 (12) | 0.0718 (14) | 0.0634 (13) | −0.0117 (10) | 0.0005 (10) | −0.0038 (10) |
C8 | 0.0495 (10) | 0.0603 (11) | 0.0513 (11) | −0.0038 (8) | 0.0147 (8) | −0.0033 (8) |
C9 | 0.0676 (13) | 0.0903 (16) | 0.0584 (14) | 0.0158 (11) | 0.0217 (10) | 0.0089 (11) |
C10 | 0.0542 (11) | 0.0711 (14) | 0.0938 (18) | −0.0107 (10) | 0.0132 (11) | 0.0141 (12) |
C11 | 0.0587 (12) | 0.0594 (12) | 0.0917 (17) | −0.0093 (10) | 0.0079 (11) | −0.0037 (11) |
C12 | 0.0482 (10) | 0.0538 (10) | 0.0563 (12) | −0.0028 (8) | 0.0015 (8) | 0.0027 (8) |
C13 | 0.0543 (10) | 0.0534 (10) | 0.0569 (12) | 0.0020 (8) | 0.0061 (8) | −0.0050 (8) |
C14 | 0.0486 (10) | 0.0600 (11) | 0.0534 (11) | −0.0017 (8) | 0.0097 (8) | 0.0042 (8) |
C15 | 0.0546 (10) | 0.0527 (11) | 0.0618 (13) | −0.0058 (8) | 0.0078 (8) | 0.0018 (8) |
C16 | 0.0592 (11) | 0.0502 (10) | 0.0538 (12) | 0.0011 (8) | 0.0053 (8) | −0.0016 (8) |
C17 | 0.0479 (9) | 0.0530 (10) | 0.0502 (10) | 0.0031 (8) | 0.0064 (7) | 0.0072 (8) |
C18 | 0.0780 (16) | 0.1011 (19) | 0.110 (2) | 0.0006 (14) | 0.0436 (14) | −0.0225 (15) |
C19 | 0.112 (2) | 0.0623 (15) | 0.128 (3) | 0.0008 (14) | 0.0042 (18) | 0.0030 (15) |
N1—C10 | 1.362 (3) | C7—H7A | 0.9300 |
N1—C17 | 1.385 (2) | C9—H9A | 0.9700 |
N1—C9 | 1.465 (3) | C9—H9B | 0.9700 |
N2—C1 | 1.377 (3) | C10—C11 | 1.359 (3) |
N2—C8 | 1.381 (3) | C10—H10A | 0.9300 |
N2—H1N2 | 0.88 (2) | C11—C12 | 1.419 (3) |
O1—C14 | 1.390 (2) | C11—H11A | 0.9300 |
O1—C18 | 1.411 (3) | C12—C17 | 1.401 (3) |
O2—C5 | 1.379 (3) | C12—C13 | 1.408 (3) |
O2—C19 | 1.398 (3) | C13—C14 | 1.364 (3) |
C1—C2 | 1.349 (3) | C13—H13A | 0.9300 |
C1—C9 | 1.488 (3) | C14—C15 | 1.402 (3) |
C2—C3 | 1.431 (3) | C15—C16 | 1.376 (3) |
C2—H2A | 0.9300 | C15—H15A | 0.9300 |
C3—C8 | 1.400 (3) | C16—C17 | 1.387 (3) |
C3—C4 | 1.406 (3) | C16—H16A | 0.9300 |
C4—C5 | 1.374 (3) | C18—H18A | 0.9600 |
C4—H4A | 0.9300 | C18—H18B | 0.9600 |
C5—C6 | 1.396 (3) | C18—H18C | 0.9600 |
C6—C7 | 1.367 (3) | C19—H19A | 0.9600 |
C6—H6A | 0.9300 | C19—H19C | 0.9600 |
C7—C8 | 1.385 (3) | C19—H19D | 0.9600 |
C10—N1—C17 | 107.95 (17) | H9A—C9—H9B | 107.6 |
C10—N1—C9 | 126.61 (18) | C11—C10—N1 | 110.38 (18) |
C17—N1—C9 | 125.33 (17) | C11—C10—H10A | 124.8 |
C1—N2—C8 | 108.88 (17) | N1—C10—H10A | 124.8 |
C1—N2—H1N2 | 127.1 (16) | C10—C11—C12 | 107.10 (19) |
C8—N2—H1N2 | 123.6 (16) | C10—C11—H11A | 126.5 |
C14—O1—C18 | 117.49 (17) | C12—C11—H11A | 126.5 |
C5—O2—C19 | 118.1 (2) | C17—C12—C13 | 119.31 (16) |
C2—C1—N2 | 108.97 (18) | C17—C12—C11 | 106.74 (18) |
C2—C1—C9 | 129.2 (2) | C13—C12—C11 | 133.94 (19) |
N2—C1—C9 | 121.79 (19) | C14—C13—C12 | 118.18 (17) |
C1—C2—C3 | 108.28 (17) | C14—C13—H13A | 120.9 |
C1—C2—H2A | 125.9 | C12—C13—H13A | 120.9 |
C3—C2—H2A | 125.9 | C13—C14—O1 | 124.04 (18) |
C8—C3—C4 | 119.24 (18) | C13—C14—C15 | 121.81 (18) |
C8—C3—C2 | 106.12 (17) | O1—C14—C15 | 114.14 (16) |
C4—C3—C2 | 134.64 (18) | C16—C15—C14 | 120.99 (17) |
C5—C4—C3 | 118.42 (19) | C16—C15—H15A | 119.5 |
C5—C4—H4A | 120.8 | C14—C15—H15A | 119.5 |
C3—C4—H4A | 120.8 | C15—C16—C17 | 117.50 (17) |
C4—C5—O2 | 124.4 (2) | C15—C16—H16A | 121.2 |
C4—C5—C6 | 121.1 (2) | C17—C16—H16A | 121.2 |
O2—C5—C6 | 114.5 (2) | N1—C17—C16 | 129.98 (18) |
C7—C6—C5 | 121.5 (2) | N1—C17—C12 | 107.83 (16) |
C7—C6—H6A | 119.3 | C16—C17—C12 | 122.19 (18) |
C5—C6—H6A | 119.3 | O1—C18—H18A | 109.5 |
C6—C7—C8 | 117.88 (19) | O1—C18—H18B | 109.5 |
C6—C7—H7A | 121.1 | H18A—C18—H18B | 109.5 |
C8—C7—H7A | 121.1 | O1—C18—H18C | 109.5 |
N2—C8—C7 | 130.36 (18) | H18A—C18—H18C | 109.5 |
N2—C8—C3 | 107.76 (17) | H18B—C18—H18C | 109.5 |
C7—C8—C3 | 121.86 (19) | O2—C19—H19A | 109.5 |
N1—C9—C1 | 114.58 (18) | O2—C19—H19C | 109.5 |
N1—C9—H9A | 108.6 | H19A—C19—H19C | 109.5 |
C1—C9—H9A | 108.6 | O2—C19—H19D | 109.5 |
N1—C9—H9B | 108.6 | H19A—C19—H19D | 109.5 |
C1—C9—H9B | 108.6 | H19C—C19—H19D | 109.5 |
C8—N2—C1—C2 | −0.1 (2) | N2—C1—C9—N1 | 63.6 (3) |
C8—N2—C1—C9 | 178.52 (17) | C17—N1—C10—C11 | −0.4 (2) |
N2—C1—C2—C3 | 0.3 (2) | C9—N1—C10—C11 | −176.8 (2) |
C9—C1—C2—C3 | −178.2 (2) | N1—C10—C11—C12 | 0.0 (3) |
C1—C2—C3—C8 | −0.3 (2) | C10—C11—C12—C17 | 0.5 (2) |
C1—C2—C3—C4 | 179.3 (2) | C10—C11—C12—C13 | 179.3 (2) |
C8—C3—C4—C5 | −0.7 (3) | C17—C12—C13—C14 | 1.4 (3) |
C2—C3—C4—C5 | 179.7 (2) | C11—C12—C13—C14 | −177.2 (2) |
C3—C4—C5—O2 | 179.0 (2) | C12—C13—C14—O1 | 177.71 (17) |
C3—C4—C5—C6 | −1.1 (3) | C12—C13—C14—C15 | −1.6 (3) |
C19—O2—C5—C4 | −17.5 (4) | C18—O1—C14—C13 | −2.9 (3) |
C19—O2—C5—C6 | 162.6 (2) | C18—O1—C14—C15 | 176.4 (2) |
C4—C5—C6—C7 | 1.6 (4) | C13—C14—C15—C16 | 0.9 (3) |
O2—C5—C6—C7 | −178.5 (2) | O1—C14—C15—C16 | −178.47 (17) |
C5—C6—C7—C8 | −0.2 (3) | C14—C15—C16—C17 | 0.0 (3) |
C1—N2—C8—C7 | 178.2 (2) | C10—N1—C17—C16 | −178.4 (2) |
C1—N2—C8—C3 | −0.1 (2) | C9—N1—C17—C16 | −1.9 (3) |
C6—C7—C8—N2 | −179.7 (2) | C10—N1—C17—C12 | 0.7 (2) |
C6—C7—C8—C3 | −1.6 (3) | C9—N1—C17—C12 | 177.15 (18) |
C4—C3—C8—N2 | −179.48 (17) | C15—C16—C17—N1 | 178.80 (18) |
C2—C3—C8—N2 | 0.3 (2) | C15—C16—C17—C12 | −0.2 (3) |
C4—C3—C8—C7 | 2.1 (3) | C13—C12—C17—N1 | −179.73 (16) |
C2—C3—C8—C7 | −178.18 (18) | C11—C12—C17—N1 | −0.7 (2) |
C10—N1—C9—C1 | −105.6 (2) | C13—C12—C17—C16 | −0.5 (3) |
C17—N1—C9—C1 | 78.6 (3) | C11—C12—C17—C16 | 178.44 (17) |
C2—C1—C9—N1 | −118.1 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O1i | 0.88 (2) | 2.24 (3) | 3.037 (2) | 151 (2) |
Symmetry code: (i) x−1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C19H18N2O2 |
Mr | 306.35 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 9.4446 (5), 19.5625 (8), 8.6657 (5) |
β (°) | 98.903 (4) |
V (Å3) | 1581.78 (14) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.68 |
Crystal size (mm) | 0.92 × 0.20 × 0.06 |
Data collection | |
Diffractometer | Bruker APEXII CCD |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.575, 0.961 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9421, 2584, 2087 |
Rint | 0.041 |
(sin θ/λ)max (Å−1) | 0.588 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.133, 1.06 |
No. of reflections | 2584 |
No. of parameters | 215 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.15, −0.14 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O1i | 0.88 (2) | 2.24 (3) | 3.037 (2) | 151 (2) |
Symmetry code: (i) x−1, y, z. |
Footnotes
‡Thomson Reuters ResearcherID: A-3561-2009.
Acknowledgements
The authors thank the Deanship of Scientific Research and the Research Center of the College of Pharmacy, King Saud University, for supporting this study. HKF and SA thank Universiti Sains Malaysia (USM) for the Research University Grant (1001/PFIZIK/811160). SA also thanks the Malaysian Government and USM for the Academic Staff Training Scheme (ASTS) award.
References
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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.
Melatonin (N-acetyl-5-methoxytryptamine, MLT) is primarily produced by the pineal gland in the brain with a marked circadian rhythm normally peaking in the dark to regulate sleep. MLT acts through activation of two G-protein-coupled receptors, designated as MT1 and MT2 (Csernus & Mess, 2003). In addition, a low-affinity putative MLT binding site called MT3 has been recently characterized as a melatonin-sensitive form of the human enzyme quinine reductase 2 (Nosjean et al., 2000). MLT has found widespread use in the treatment of sleep disorders. Other effects described in the literature include its anti-inflammatory, pain modulatory, antitumor, and antioxidant properties (Blask et al., 2002; Genovese et al., 2005; Mills et al., 2005; Peres, 2005; Sofic et al., 2005; Witt-Enderby et al., 2006). The title compound is an intermediate which could yield, via the reported procedure (Attia et al., 2008), various MLT analogues which can be evaluated for their potency and selectivity for MLT receptor subtypes.
In the title compound (Fig. 1), the indole ring systems (N1/C10–C17 & N2/C1–C8) are essentially planar with maximum deviations of 0.015 (2) Å at atom C10 and C2, respectively. In addition, the indole ring systems are almost perpendicular to each other with dihedral angle of 72.17 (7)°. Bond lengths and angles are within the normal range and are comparable to those in the related structures (Narayanan et al., 2011; Deng et al., 2011).
The crystal structure is shown in Fig. 2. The molecules are linked into one dimensional zigzag chains along a-axis via N2—H1N2···O1 interactions (Table 1).