Methyl N-(3-cyanopicolinoyl)-l-tryptophanate

In the title compound, C19H16N4O3, the stereocenter has an l configuration; l-tryptophan methyl ester hydrochloride being used as a starting material. The indole ring system and the pyridine ring are inclined to one another by 13.55 (14)°. In the crystal, adjacent molecules are linked via N—H⋯O hydrogen bonds, forming chains propagating along the c-axis direction.

In the title compound, C 19 H 16 N 4 O 3 , the stereocenter has an l configuration; l-tryptophan methyl ester hydrochloride being used as a starting material. The indole ring system and the pyridine ring are inclined to one another by 13.55 (14) . In the crystal, adjacent molecules are linked via N-HÁ Á ÁO hydrogen bonds, forming chains propagating along the c-axis direction.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2666).

Comment
Cyano substituted compounds like the title compound are useful as intermediates in the synthesis of N-hydroxybenzamidines (Peterlin-Mašič & Kikelj, 2001). Substituted N-hydroxybenzamidines as well as their heterocyclic analogs are key intermediates in the synthesis of pharmaceutically important derivatives of 1,2,4-oxadiazole. The latter are well known for their anticancer (Kundu et al., 2012), anti-HIV (Sakamoto et al., 2007), and anti-microbial activities (Tyrkov & Sukhenko, 2004). In our studies on N-hydroxyamidines, of a heterocyclic nature from corresponding cyano derivatives, we synthesized the title compound and report herein on its crystal structure.
In the crystal, adjacent molecules are linked via N-H···O hydrogen bonds, forming chains propagating along the c axis direction (Table 1).

Experimental
The title compound was synthesized according to the literature procedure (Devillers et al., 2002). 2-Cyanonicotinic acid (5 mmol) was dissolved in CH 2 Cl 2 (30 ml), then triethylamine (10 mmol), L-tryptophan methyl ester hydrochloride (5 mmol) and N-hydroxybenzotriazole (5 mmol) were added to the solution. The mixture was stirred at 273 K and EDCI (5.05 mmol; 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydroiodide) was added. Then, the mixture was stirred at room temperature over night. The residue was diluted in CH 2 Cl 2 , washed with a solution of 0.1M HCl (3 × 15 ml), brine (20 ml) and then dried over MgSO 4 and concentrated under vacuo. The solid obtained was purified by column chromatography (CH 2 Cl 2 :MeOH 94:6). The title compound is a byproduct and crystallized as pale-yellow block-like crystals, suitable for X-ray diffraction analysis, by slow evaporation of a solution in dichloromethane and methanol (9:1).

Refinement
All H atoms were placed in idealized positions and constrained to ride on their parent atoms: N-H = 0.86 Å, C-H = 0.93, 0.98, 0.97 and 0.96 Å for H(aromatic), methine, methylene and methyl H atoms, respectively, with U iso = 1.5U eq (Cmethyl) and = 1.2U eq (N,C) for other H atoms.