Methyl 3-(1H-indole-3-carboxamido)propionate hemihydrate

The title compound, C13H14N2O3·0.5H2O, was synthesized by the condensation of methyl 3-aminopropionate with 3-trichloroacetylindole. The two organic molecules in the asymmetric unit are both close to planar, with r.m.s. deviations from the best fit plane through all of the non-H atoms of 0.004 (2) Å for molecule A and 0.006 (1) Å for molecule B. Also, the five- and six-membered rings of the indole systems are inclined at 1.67 (8) and 1.50 (8)° in molecules A and B, respectively. In the crystal structure, the organic molecules are connected by intermolecular N—H⋯O hydrogen bonds, forming chains. O—H⋯O and N—H⋯O hydrogen-bond interactions involving the water molecules interlink these chains, forming double chains approximately parallel to the a axis.

The title compound, C 13 H 14 N 2 O 3 Á0.5H 2 O, was synthesized by the condensation of methyl 3-aminopropionate with 3trichloroacetylindole. The two organic molecules in the asymmetric unit are both close to planar, with r.m.s. deviations from the best fit plane through all of the non-H atoms of 0.004 (2) Å for molecule A and 0.006 (1) Å for molecule B. Also, the five-and six-membered rings of the indole systems are inclined at 1.67 (8) and 1.50 (8) in molecules A and B, respectively. In the crystal structure, the organic molecules are connected by intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains. O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen-bond interactions involving the water molecules interlink these chains, forming double chains approximately parallel to the a axis.   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x þ 1; y À 1; z; (ii) Àx þ 1; Ày þ 1; Àz; (iii) Àx; Ày þ 2; Àz.
The asymmetric unit of the title compound comprises two substituted indole molecules, A & B and a solvent water molecule, Fig. 1. The organic molecules are each reasonably planar with rms deviations from the best fit plane through all of the non hydrogen atoms of 0.004 (2) Å for A and -0.006 (1) Å for B. Also the five and six-membered rings of the indole systems are inclined at 1.67 (8) ° and 1.50 (8) ° in A and B respectively. Bond lengths in both molecules are unexceptional (Allen et al., 1987) and are comparable to those found in similar structures (Huang et al., 2009;Siddiquee et al., 2009).
In the crystal structure, molecules of the organic compound are linked through N-H···O H-bonds to form dimers that are connected by another N-H···O H-bonds to generate chains, and the O-H(W)···O and N-H···O(W) H-bond interactions link these chains to form double-chains extending to the a axis (Table 1, Fig. 2).

Experimental
The hydrochloride salt of methyl 3-aminopropionate (0.70 g, 5 mmol) and 3-trichloroacetylindole (1.32 g, 5 mmol) were added to acetonitrile (10 ml), followed by the dropwise addition of triethylamine (1.2 ml). The mixture was stirred at room temperature for 16 h and then poured into water. After filtration, the precipitate was collected as a yellow solid. The impure product was dissolved in EtOH at room temperature. Light yellow monoclinic crystals suitable for X-ray analysis (m.p. 409 K, 86.2% yield) grew over a period of one week when the solution was exposed to the air.

Refinement
All non-H atoms were refined with anisotropic displacement parameters. The H atoms bound to C and N were positioned geometrically [C-H = 0.99Å for CH 2 , 0.98Å for CH 3 , 0.95Å for CH(aromatic) and N-H = 0.88 Å] and refined using a riding model, with U iso = 1.2U eq (1.5U eq for the methyl group) of the parent atom. The water H atoms were located in a difference Fourier map and were constrained in these positions with O-H = 0.8497 and 0.8533, and with U iso = 1.5U eq (O). Fig. 1. The asymmetric unit of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Special details
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.
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 Rfactors(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.