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

Qiang Guo; Lanying Sun; Huiyuan Guo; Mingliang Liu

doi:10.1107/S1600536809004772

. 2009 Feb 21;65(Pt 3):o580. doi: 10.1107/S1600536809004772

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

Qiang Guo ^a, Lanying Sun ^a, Huiyuan Guo ^a, Mingliang Liu ^a,^*

PMCID: PMC2968450 PMID: 21582235

Abstract

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.

Related literature

For properties of quinolone derivatives, see: Ball et al. (1998 ▶); Ray et al. (2005 ▶). For the synthesis of new quinolones, see: Anderson & Osheroff (2001 ▶); Choi et al. (2004 ▶); Wang, Guo et al. (2008 ▶). For some crystal structures of quinolones, see: Wang, Liu et al. (2008 ▶).

Experimental

Crystal data

C₈H₁₈N₄O₂ ²⁺·2Cl⁻
M _r = 273.16
Orthorhombic,
a = 12.7355 (14) Å
b = 8.8506 (12) Å
c = 26.334 (2) Å
V = 2968.3 (6) Å³
Z = 8
Mo Kα radiation
μ = 0.43 mm⁻¹
T = 298 K
0.23 × 0.20 × 0.19 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.907, T _max = 0.922
14370 measured reflections
2597 independent reflections
1986 reflections with I > 2σ(I)
R _int = 0.062

Refinement

R[F ² > 2σ(F ²)] = 0.077
wR(F ²) = 0.210
S = 1.08
2597 reflections
170 parameters
H-atom parameters constrained
Δρ_max = 0.44 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Data collection: SMART (Bruker, 1998 ▶); cell refinement: SAINT (Bruker, 1999 ▶); data reduction: SAINT and SHELXTL (Sheldrick, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809004772/pk2146sup1.cif

e-65-0o580-sup1.cif^{(19.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809004772/pk2146Isup2.hkl

e-65-0o580-Isup2.hkl^{(127.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3B⋯Cl1	0.86	2.29	3.144 (4)	173
N3—H3A⋯Cl1ⁱ	0.86	2.41	3.213 (4)	156
N2—H2⋯Cl2ⁱⁱ	0.86	2.21	3.029 (4)	160
N1—H1B⋯Cl2	0.90	2.18	3.035 (4)	159
N1—H1A⋯Cl1ⁱⁱⁱ	0.90	2.20	3.076 (4)	165

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

This work was supported by the IMB Research Foundation.

supplementary crystallographic information

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)

Experimental

To a stirring solution of N'-methoxy-(1-N-tert-butoxycarbonyl-4- ethoxyimino) pyrrolidine-3-carboximidamide (15.0 g, 50.0 mmol) in methanol (80 ml) was pumped into dry hydrogen chloride for 2 h at room temperature. After the removal of the methanol under reduced pressure, the residue was treated with ethyl acetate (80 ml), and filtered. The filter cake was washed with ethyl acetate and ether, respectively, dried in vacuo to give the title compound as a white solid (11.5 g, 84.2%; mp: 375–376 K). Single crystals suitable for X-ray analysis were obtained by slow evaporation of a methanol/ ethyl acetate (1:1 v/v). ¹H NMR(DMSO-d₆, δ):1.14–1.17(3H, m, CH₃), 3.44–3.58(m, 1H, pyrrolidine), 3.53(2H, br, NH₂⁺), 3.66(3H, s, OCH₃), 3.68–3.79(2H, m, OCH₂), 4.03–4.11(4H, m, pyrrolidine), 9.88–9.93(3H, br, NH₂, NH⁺). MS(ESI, m/z): 201(M+H)⁺.