3-Carbamoylquinoxalin-1-ium chloride

The title compound, C9H8N3O+·Cl−, was isolated from a liquid culture of streptomyces sp. In the cation, the ring system makes a dihedral angle of 0.2 (2)° with the amide group. The protonation creating the cation occurs at ome of the N atoms in the quinoxaline ring system. In the crystal, the ions are linked through N—H⋯O and N—H⋯Cl hydrogen bonds, forming a two-dimensional network parallel to (10).

The title compound, C 9 H 8 N 3 O + ÁCl À , was isolated from a liquid culture of streptomyces sp. In the cation, the ring system makes a dihedral angle of 0.2 (2) with the amide group. The protonation creating the cation occurs at ome of the N atoms in the quinoxaline ring system. In the crystal, the ions are linked through N-HÁ Á ÁO and N-HÁ Á ÁCl hydrogen bonds, forming a two-dimensional network parallel to (103).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LH5381).

Comment
The quinoxaline ring is an essential component of the DNA intercalators echinomycin and triostin A. The two quinoxaline rings present in each of these compounds bind the minor groove of double stranded DNA and thereby inhibit RNA synthesis (Bailly et al., 1999;May et al., 2004;Mollegaard et al., 2000;Waring, 1993). Presently, the quinoxaline ring has been characterized crystallographically only as part of a significantly larger molecular assembly (Hossain et al., 1982;Sheldrick et al.,1984;Sheldrick et al., 1995;Viswamitra et al., 1981;Wang et al., 1984;Ughetto et al., 1985). Accordingly, the resolution of the quinoxaline moieties currently established is relatively low. Here, characterization of a simpler quinoxaline ring system provides a higher resolution dataset for a compound having a substitution pattern identical to that found in the quinoxaline antibiotics. The conformation about the C1-C2 bond in the title compound is shown in Figure 1 and matches that reported for triostin A and echinomycin. Molecules in the crystal are linked through N1-H···O1 i (see Table 1 for symmetry codes) hydrogen bonds as well as N1-H···Cl···H-N3 interaction. The structure viewed along the a axis is shown in figure 2.

Experimental
The title compound was obtained by liquid-liquid extraction (CH 2 Cl 2 /H 2 O) of a culture of an endophytic Streptomyces sp.
described elsewhere (Castillo et al., 2003). A crystal was grown by slow evaporation of a 1:1 mix of CHCl 3 :MeOH

Refinement
All H atoms were refined independently with isotropic displacement parameters. Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are shown at the 50% probability level on non-hydrogen atoms.   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.