6-Aminonicotinamide

In the title compound, C6H7N3O, the amide group is rotated such that the carbonyl O atom is syn to the pyridine N atom, with an O—C—C—C torsion angle of −23.55 (18)°. The crystal packing involves four hydrogen bonds of the types N—H⋯N and N—H⋯O. Two separate centrosymmetric rings are formed using N—H⋯N and N—H⋯O hydrogen bonds that result in a ribbon of 6-aminonicotinamide molecules, joined by the amide and amine functional groups. The remaining two hydrogen bonds are used to generate a three-dimensional packing arrangement.

In the title compound, C 6 H 7 N 3 O, the amide group is rotated such that the carbonyl O atom is syn to the pyridine N atom, with an O-C-C-C torsion angle of À23.55 (18) . The crystal packing involves four hydrogen bonds of the types N-HÁ Á ÁN and N-HÁ Á ÁO. Two separate centrosymmetric rings are formed using N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds that result in a ribbon of 6-aminonicotinamide molecules, joined by the amide and amine functional groups. The remaining two hydrogen bonds are used to generate a threedimensional packing arrangement.

6-Aminonicotinamide Lerato P. Ntsala and Andreas Lemmerer Comment
The title compound, 6-aminonicotinamide, and commonly abbreviated to 6AN, is a potent inhibitor of the pentose phosphate pathway (PPP) enzyme, 6PG dehydeogenase, which is an important step in the synthesis of NADPH and ribose units required for biosynthesis and DNA repair (Street et al., 1997). Inhibition of this enzyme by 6-AN leads to accumulation of 6PG. In addition, it has been used in preclinical trials to enhance the effectiveness of cisplatin (Budihardjo et al., 2000). To date, its crystal structure has not been reported.
The asymmetric unit of (I) consists of one molecule of 6AN on a general position and Fig. 1 shows the atomic numbering scheme. There are two single bonds allowing for torsional freedom, the amide group and the amine group, both relative to the pyridine ring. The torsion angle O1-C6-C1-C2 of -23.55 (18) is indicative of a syn conformation of the carbonyl to the pyridine N atom. This conformation is opposite to that of any of the polymorphs of the parent unsubstituted compound, nicotinamide, where the torsion angle ranges from -157.6 (1) to 167.1 (1)° (Miwa et al., 1999;Li et al., 2011). The hydrogen bonding of (I) makes use of all four hydrogen atom donors, two on the amide group and two on the amine. The syn H on the amide forms a homomeric centrosymmetric dimer using N1-H1S···O1 hydrogen bonds, while the H atom syn to the pyridine forms a second centrosymmetric dimer by hydrogen bonding to the pyridine, using N3-H3S···.N2 hydrogen bonds. The combination of these two dimers results in 1-D ribbons extended along the [110] direction. These ribbons are joined by N--H···O hydrogen bonds from the anti H on the amide group (Fig. 2).
Ultimately a 3-D arrangement results (Fig. 3), further supported by the N3-H3A···N3 hydrogen bond from the second H atom on the amine (not shown for clarity in Fig. 3).

Experimental
Crystals of (I) where grown by dissolving 0.200 g (1.46 mmol) in 10 ml of AR-grade methanol and allowing for slow evaporation at room temperature over a few days. Cube-like colourless crystals where obtained.

Refinement
The C-bound H atoms were geometrically placed (C-H bond lengths of 0.95 for aromatic CH) and refined as riding with U iso (H) = 1.2U eq (C). The N-bound H atoms were located in the difference map and coordinates refined freely together with their isotropic thermal parameters.

Special details
Experimental. Absorption corrections were made using the program SADABS (Sheldrick, 1996) 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.  (17)