N'-[(E)-4-Meth-oxy-benzyl-idene]-2-(5-meth-oxy-2-methyl-1H-indol-3-yl)acetohydrazide.

The conformation adopted by the title compound, C20H21N3O3, in the crystal is 'J'-shaped and appears to be at least partially directed by a weak intra-molecular C-H⋯N hydrogen bond. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds, forming dimers with R 2 (2)(8) motifs. Furthermore, these dimers connect to each other via C-H⋯O and N-H⋯O hydrogen bonds to form a three-dimensional network.

The conformation adopted by the title compound, C 20 H 21 -N 3 O 3 , in the crystal is 'J'-shaped and appears to be at least partially directed by a weak intramolecular C-HÁ Á ÁN hydrogen bond. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds, forming dimers with R 2 2 (8) motifs. Furthermore, these dimers connect to each other via C-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds to form a threedimensional network.

Comment
Indomethacin like other non-steroidal anti-inflammatory drugs (NSAIDs) is widely used in treatment of pain, fever, and inflammation (Richy et al., 2004). Prolonged administration of such drugs is commonly associated with several undesired side-effects. The most common of these are gastrointestinal hemorrhage, ulceration, and decreased renal function (Allison et al., 1992;McMahon 2001;Rocha et al., 2001). The existence of a free carboxylic acid group in the parent drug has been considred to be the major factor in establishing superficial stomach erosion, particularly in the corpus region of the stomach (Halen et al., 2009). Thus, it was considered essential to mask or to remove this functional group in order to produce a safer and more tolerant prodrug profile. Following this reasoning, we report here the synthesis and crystal structure of the title compound.
The "J" shaped conformation of the title molecule (I) is shown in Fig. 1. The bond lengths and bond angles of (I) compare well with those in related compounds (Mague et al., 2013).

Experimental
A mixture of 233 mg (1 mmol) 2-(5-methoxy-2-methyl-1H-indol-3-yl)acetohydrazide and 136 mg (1 mmol) of 4-methoxybenzaldehyde in 30 ml ethanol containing few drops of glacial acetic acid was refluxed for 5 h. The reaction mixture was allowed to cool to room temperature and the excess solvent was evaporated under vacuum. The residual solid was collected, washed with cold ethanol and recrystallized from ethanol. Colourless blocks of X-ray quality were obtained.

Refinement
The H atoms of the amino group were found in the difference Fourier maps, and were refined freely. C-bound H atoms were placed geometrically and refined using a riding model with C-H = 0.95 -0.99 Å, and with U iso (H) = 1.2 or 1.5U iso (C).

Figure 1
Perspective view of the title compound with 50% probability displacement ellipsoids.

Figure 2
Packing viewed along a showing the hydrogen bonds as dotted lines.  Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.