tert-Butyl N-{[5-(5-oxohexanamido)pyridin-2-yl]amino}carbamate

In the crystal structure of the title compound, C16H24N4O4, molecules are linked by N—H⋯O hydrogen bonds between the carbonyl groups of the carbamoyl and amido functional groups and the amino groups, and by N—H⋯N hydrogen bonds between the amino group and the pyridine ring, forming two-dimensional networks parallel to the ab plane.

In the crystal structure of the title compound, C 16 H 24 N 4 O 4 , molecules are linked by N-HÁ Á ÁO hydrogen bonds between the carbonyl groups of the carbamoyl and amido functional groups and the amino groups, and by N-HÁ Á ÁN hydrogen bonds between the amino group and the pyridine ring, forming two-dimensional networks parallel to the ab plane.

Comment
Radioisotopes conjugated to proteins provide a means for imaging and treatment of disease. The bifunctional 2hydrazinopyridine derivatives are useful linker molecules for attaching metal ions such as 99m Tc to macromolecules (Ardisson et al., 2005;Jurisson & Lydon, 1999). Hence, this 2-hydrazinopyridinyl moiety has previously been used for labeling bioactive molecules (Abrams et al., 1994;Banerjee et al. 2005;Rose et al., 1998;Schwartz et al., 1990). Thus, the use of Tc-labeled hydrazine derivatives continues to undergo further development (Liu et al., 2011;Lu et al., 2011).
The wide spectrum of medicinal applications of this class of radiolabeled chelates prompted us to work in this domain and we report herein on the synthesis and crystal structure of the title compound, designed as a potential chelate for 99m Tc.
The title compound, C 16 H 24 N 4 O 4 , has the triclinic (P1) symmetry. It crystalizes with one molecule in the asymmetric unit. In the crystal, the molecules are linked together by N-H···O hydrogen bonding between the carbonyl groups of the carbamoyl and amido functional groups and the amino groups and by N-H···N hydrogen bonding between amino and pyridine moiety leading to a two-dimensional network within the ab plane. The network cohesion in the 3 rd direction is assured by Van der Waals interactions and H-bond like interactions between the carbonyl and the BOC group.

Experimental
To a stirred solution of 5-oxohexanoic acid (2.45 mmol) in 15 ml of tetrahydrofurane was added triethylamine (2.45 mmol). After 10 min of stirring at room temperature was added isobutyl chloroformate (2.45 mmol). The reaction mixture was stirred at room temperature for 5 h, then 2-(t-butoxycarbonyl hydrazine)-5-amino-pyridine (2.23 mmol) (Cugola et al.,19955) was added and the reaction stirred for 12 h. The mixture was evaporated to dryness, and the residue was triturated in water. The solid precipitate was filtered off and washed with water then with ethanol, and purified by column chromatography using CHCl 3 /methanol (9/1, v/v) as eluent to give the title compound as white crystals (R f = 1/4).

Refinement
Crystallographic data were collected at 293 K on a Brucker nonius k-CCD diffractometer with monochromatic Mo-Kα radiation (λ = 0.71073 Å). At 293 K, the full sphere data collection was performed using φ scans and ω scans. The unit cell determination and data reduction were performed using DIRAX/LSQ (Duisenberg, 1992) and Collect (Nonius, 1998) programs on the full set of data. The crystal structure was solved by direct methods and successive Fourier difference supplementary materials sup-2 Acta Cryst. (2013). E69, o1531-o1532 syntheses with SHELXS97 program (Sheldrick, 2008). The refinements of the crystal structure were performed on F2 by weighted anisotropic full-matrix least squares methods using the SHELXL97 program (Sheldrick, 2008). Both pieces of software were used within OLEX2 package (Dolomanov et al., 2009). All the non-H atoms were refined with anisotropic temperature parameters. The positions of the H atoms were deduced from coordinates of the non-H atoms and confirmed by Fourier synthesis and treated according to the riding model during refinement with isotropic displacement parameters, corresponding to the atom they are linked to. H atoms were included for structure factor calculations but not refined.

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
Crystal packing of the title compound viewed down the a axis. Only hydrogen atoms involved in hydrogen bonding (dashed lines) are shown.