5-Methoxy-1-[(5-methoxy-1H-indol-2-yl)methyl]-1H-indole

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.

In the title compound, C 19 H 18 N 2 O 2 , 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-HÁ Á ÁO hydrogen bonds.

Experimental
Data collection: APEX2 (Bruker, 2009); cell refinement: 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 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 MT 1 and MT 2 (Csernus & Mess, 2003). In addition, a low-affinity putative MLT binding site called MT 3 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).

Experimental
(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 LiAlH 4 /AlCl 3 in dry diethyl ether (prepared by a slow addition of AlCl 3 (0.32 g, 2.41 mmol) to a suspension LiAlH 4 (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 (Na 2 SO 4 ) and evaporated under reduced pressure. The residue was purified by silica gel chromatography (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).

Figure 1
The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.

Special details
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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.