(2RS)-3-Hydroxy-2-methyl-2-(2-pyridyl)imidazolidine-4-one

The title structure, C9H11N3O2, is a racemate. The chiral centre is situated at the N—C—N C atom of the imidazolidine ring. The interplanar angle between the mean planes of the pyridine and imidazolidine rings is 89.41 (5)°. The methyl group is in a trans position with respect to the pyridine N atom. In the crystal, the molecules are arranged in zigzag layers parallel to the b axis. The molecules within the layers are interconnected by strong O—H⋯N and weak N—H⋯O hydrogen bonds; the former take place between OH groups and amine N atoms and the latter between the amine N atom and the carbonyl O atom. In addition, C—H⋯O interactions are also present.

The title structure, C 9 H 11 N 3 O 2 , is a racemate. The chiral centre is situated at the N-C-N C atom of the imidazolidine ring. The interplanar angle between the mean planes of the pyridine and imidazolidine rings is 89.41 (5) . The methyl group is in a trans position with respect to the pyridine N atom. In the crystal, the molecules are arranged in zigzag layers parallel to the b axis. The molecules within the layers are interconnected by strong O-HÁ Á ÁN and weak N-HÁ Á ÁO hydrogen bonds; the former take place between OH groups and amine N atoms and the latter between the amine N atom and the carbonyl O atom. In addition, C-HÁ Á ÁO interactions are also present.
These properties have provoked current interest in the development of novel synthetic routes for preparation of new selective hydroxamate chelating agents and siderophore mimics. Recently it was found that the reactions of α-amino hydroxamic acids with aldehydes and ketons do not result in the open-chain Schiff base hydroxamic acids but afford fivemembered cyclic products containing residues of 3-hydroxyimidazolidine-4-one (Marson & Pucci, 2004;Vystorop et al., 2002;Vystorop et al., 2003). Here we describe a crystal structure of the title structure, 2-methyl-2-(pyridine-2-yl)-3-hydroxyimidazolidine-4-one, obtained as a result of the condensation of glycine hydroxamic acid and 2-acetylpyridine.
The molecules of the title structure are interconnected by the H-bonds. The molecules contain a chiral centre at the C2 atom ( Fig. 1) and the structure is a racemate. The molecule is not planar: the interplanar angle between the mean planes of the pyridine and imidazolidine rings equals to 89.41 (5)°. The imidazolidine ring exhibits the envelope conformation: the C2 atom is displaced by 0.320 (2) Å out of the mean plane defined by four other atoms of the ring. The methyl group is in the trans-position with respect to the pyridine nitrogen.
The bond lengths C-O, N-O and C-N in the hydroxamic function suggest the presence of the hydroxamic function in the hydroxamic form rather than in the oximic one (Świątek-Kozłowska et al., 2000). The C-N and C-C bond lengths within the pyridine ring are normal for 2-substituted pyridine derivatives (Krämer & Fritsky, 2000;Krämer et al., 2002;Kovbasyuk et al., 2004).
In the crystal packing, the molecules are arranged into zig-zagged layers by the O1-H···N2 and N2-H···O2 hydrogen bonds. These layers are parallel to the axis b. The former one takes place between NOH group and it is considered as a strong hydrogen bond (Desiraju & Steiner, 1999) while the latter one between the amine nitrogen and the carbonyl oxygen atom (Fig. 2) is considered as weak one (Desiraju & Steiner, 1999). Moreover, the mentioned layers are interconnected by C-H···O H-bonds (Tab. 1).

Experimental
A suspension of glycine hydroxamic acid (0.9 g, 10 mmol) and 2-acetylpyridine (12 mmol) in 30 ml of 96% aqueous ethanol was refluxed for at 78°C for 1-2 h. The hot reaction mixture was filtered, the filtrate produced a white precipitate on cooling. The precipitate was filtered, air-dried and recrystallized from absolute ethanol to yield the title structure as colourless prismatic crystals of average size 0.25 × 0.15 × 0.15 mm. The reagent, glycine hydroxamic acid, was prepared according to the procedure described by Cunningham et al. (1949).

Refinement
All the H-atoms were discernible in the difference electron density map. The coordinates and the isotropic displacement parameters of the hydroxyl and amine hydrogens that are involved in the strongest hydrogen bonds have been refined. The hydrogens with C atoms as their carriers were situated into the idealized positions and constrained: C-H = 0.93, 0.96 and 0.97 Å for aryl, methyl and methylene hydrogens; U iso H aryl/methylene =1.2U eq C aryl/methylene , U iso H methyl =1.5U eq C methyl .
The methyl H atoms have been refined with AFIX 137 [SHELXL98 (Sheldrick, 2008] so their positions with regard to the electron density maps have been optimized. Fig. 1. A view of the (2R)-enantiomer of the title compound, with the displacement ellipsoids shown at the 50% probability level.

Special details
Geometry. All e.s. 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.