4-Ethoxyimino-N′-methoxypyrrolidin-1-ium-3-carboximidamidium dichloride

The title compound, C8H18N4O2 2+·2Cl−, contains two oxime groups. The methyl oxime group has a Z configuration, and the ethyl oxime group is disordered, with both Z and E configurations in occupancies of 0.840 (8) and 0.160 (8), respectively. In the crystal structure, there are a number of N—H⋯Cl hydrogen bonds.


Comment
Since the discovery of norfloxacin, fluoroquinolone antibacterial agents have emerged as one of the dominant classes of chemotherapeutic drugs for the treatment of various bacterial infections (Ball et al., 1998;Ray et al., 2005). The most intensive structural variations have been carried out on the basic group at the C-7 position. In general, 5-and 6-membered nitrogen heterocycles including piperazinyl, pyrrolidinyl and piperidinyl type side chains have been proven to be the optimal substituents, as evidenced by the compounds currently on the market (Anderson & Osheroff, 2001;Choi et al., 2004).
Recently, as part of an ongoing program to find potent new fluoroquinolones displaying strong Gram-positive activity, we have focused our attention on introducing new functional groups to the pyrrolidine ring. We report here the crystal structure of the title compound, which is intended for use as a novel substituent at the C-7 position of fluoroquinolones.
There are two oximes in the molecule of the title compound (Fig. 1). The methyloxime has the Z configuration, and the ethyloxime is disordered, with both Z and E configurations at occupancy factors of 0.840 (8) and 0.160 (8), respectively.
In the molecule the N3-C5(1.296 (6) Å) bond length is significantly shorter than the normal C-N single bond (1.47 Å), indicating some delocalization over the N3-C5-N2 group. The five-membered pyrrolidine ring adopts an envelope conformation. In the crystal structure, there are a number of N-H···Cl hydrogen bonds. (Table 1)

Refinement
All H atoms were placed at calculated positions, with C-H = 0.96-0.97 Å, N-H= 0.86-0.90 Å, and included in the final cycles of refinement using a riding model, with U iso (H) = 1.2U eq (C, N) or 1.5U eq (C) for methyl H atoms.