metal-organic compounds
Potassium clavulanate
aDepartment of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo 152-8551, Japan, and bSchool of Pharmacy, Institut Teknologi Bandung, Ganesha 10, Bandung, 40312, Indonesia
*Correspondence e-mail: uekusa@cms.titech.ac.jp
The title salt, K+·C8H8NO5− [systematic name: potassium (2R,5R,Z)-3-(2-hydroxyethylidene)-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-2-carboxylate], a widely used β-lactam antibiotic, is usually chemically unstable even in the solid state owing to its tendency to be hydrolysed. In the the potassium cations are arranged along the a axis, forming interactions to the carboxylate and hydroxy groups, resulting in one-dimensional ionic columns. These columns are arranged along the b axis, connected by O—H⋯O hydrogen bonds, forming a layer in the ab plane.
Related literature
For the pharmacological activity of clavulanic acid and potassium clavulanate, see: Bird et al. (1982); Mayer & Deckwer (1996); Navarro (2005). For the hydrolysis properties of clavulanic acid and potassium clavulanate, see: Bersanetti et al. (2005); Brethauer et al. (2008); Haginaka et al. (1985); Hickey et al. (2007); Saudagar et al. (2008).
Experimental
Crystal data
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Data collection: PROCESS-AUTO (Rigaku, 1998); cell PROCESS-AUTO; data reduction: PROCESS-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
Supporting information
https://doi.org/10.1107/S1600536810027984/tk2689sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810027984/tk2689Isup2.hkl
The single crystals of potassium clavulanate were grown at a low temperature in order to prevent decomposition. After the compound was dissolved into an 8:2 mixture of methanol/water, a few drops of 1-propanol were added to the solution and the solution was kept at 235 K for a few days. The crystal used in the analysis was immediately covered with inert oil in order to prevent the decomposition through contact with atmospheric water vapor.
The O- and C-bound H atoms were geometrically placed (O–H = 0.84 Å and C–H = 0.95–1.00 Å,) and refined as riding with Uiso(H) = 1.2Ueq(carrier atom). The
was assigned according to the known configuration of the acid, an assignment confirmed by the of the (Flack, 1983).Many pathogenic bacteria secrete β-lactamases as a defense mechanism against β-lactam antibiotics. Because such β-lactamases have the potential to inactivate β-lactam antibiotics, inhibitors for these β-lactamases are clinically very important. Clavulanic acid (CA) is a powerful naturally obtained inhibitor for bacterial β-lactamases produced by the organism Streptomyces clavuligerus. Although CA itself can act as an β-lactam antibiotic and is active against a wide spectrum of Gram-positive and Gram-negative bacteria (Mayer & Deckwer, 1996), it is much more effective as a drug in combination with β-lactamase-sensitive such as amoxicillin. In that situation, CA protects the β-lactam ring of the amoxicillin from hydrolysis and can maintain its activity against β-lactamase producing bacteria (Bird et al., 1982). The CA potassium salt is widely used as a drug in injectable and solid form, especially combined with amoxicillin sodium and amoxicillin trihydrate (Navarro, 2005).
In this context, an understanding of the structure of CA is important in order to establish its ability to form molecular interactions. Unfortunately, CA is chemically unstable as are the other β-lactam antibiotics, being very sensitive to pH, temperature, and humidity via the hydrolysis degradation mechanism; (Bersanetti et al., 2005; Hickey et al., 2007; Saudagar et al., 2008). The decomposition is also self-catalyzed (Brethauer et al. 2008; Haginaka et al. 1985) and there have been some difficulties in obtaining a single crystals of CA. Therefore, until now there has been no report of a of CA. In this study, single crystals of potassium clavulanate were successfully obtained by a low-temperature crystallization process and the was determined.
In the molecular structure of potassium clavulanate, Fig. 1, the C5–O2 and C5–O3 distances of 1.262 (5)Å and 1.256 (5) Å, respectively, indicate that the negative charge of the carboxylate group is delocalised. The potassium cation is surrounded by six oxygen atoms, three O2, one O3 and two O4, deriv ed from four different clavulanate anions. The selected bond lengths around the potassium cation are listed in Table 1. These interactions are infinitely linked along the a axis and lead to an ionic (hydrophilic) column structure. These columns are connected by intermolecular O–H···O hydrogen bonds formed between O4-hydroxyl groups and carboxylate-O2 atoms, and form a hydrophobic layer in the ab plane; Fig. 2. By contrast, the remaining hydrophobic groups (i.e. bicyclo groups) form a hydrophobic layer so that the
comprises alternating hydrophilic and hydrophilic regions.For the pharmacological activity of clavulanic acid and potassium clavulanate, see: Bird et al. (1982); Mayer & Deckwer (1996); Navarro (2005). For the hydrolysis properties of clavulanic acid and potassium clavulanate, see: Bersanetti et al. (2005); Brethauer et al. (2008); Haginaka et al. (1985); Hickey et al. (2007); Saudagar et al. (2008).
Data collection: PROCESS-AUTO (Rigaku, 1998); cell
PROCESS-AUTO (Rigaku, 1998); data reduction: PROCESS-AUTO (Rigaku, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).K+·C8H8NO5− | F(000) = 488 |
Mr = 237.25 | Dx = 1.687 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71075 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 9047 reflections |
a = 4.3453 (6) Å | θ = 3.0–27.5° |
b = 7.8191 (11) Å | µ = 0.57 mm−1 |
c = 27.491 (3) Å | T = 173 K |
V = 934.1 (2) Å3 | Platet, colorless |
Z = 4 | 0.24 × 0.04 × 0.01 mm |
Rigaku R-AXIS RAPID IP area-detector diffractometer | 2138 independent reflections |
Radiation source: rotating anode, Rigaku UltraX18 | 1433 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.088 |
ω scan | θmax = 27.5°, θmin = 3.0° |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | h = −5→5 |
Tmin = 0.876, Tmax = 0.994 | k = −10→10 |
9047 measured reflections | l = −35→35 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.044 | H-atom parameters constrained |
wR(F2) = 0.118 | w = 1/[σ2(Fo2) + (0.0305P)2 + 0.8726P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max = 0.001 |
2138 reflections | Δρmax = 0.52 e Å−3 |
137 parameters | Δρmin = −0.56 e Å−3 |
0 restraints | Absolute structure: Flack (1983), 839 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.05 (9) |
K+·C8H8NO5− | V = 934.1 (2) Å3 |
Mr = 237.25 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 4.3453 (6) Å | µ = 0.57 mm−1 |
b = 7.8191 (11) Å | T = 173 K |
c = 27.491 (3) Å | 0.24 × 0.04 × 0.01 mm |
Rigaku R-AXIS RAPID IP area-detector diffractometer | 2138 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 1433 reflections with I > 2σ(I) |
Tmin = 0.876, Tmax = 0.994 | Rint = 0.088 |
9047 measured reflections |
R[F2 > 2σ(F2)] = 0.044 | H-atom parameters constrained |
wR(F2) = 0.118 | Δρmax = 0.52 e Å−3 |
S = 1.12 | Δρmin = −0.56 e Å−3 |
2138 reflections | Absolute structure: Flack (1983), 839 Friedel pairs |
137 parameters | Absolute structure parameter: −0.05 (9) |
0 restraints |
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. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
C1 | 1.2101 (11) | 0.3967 (6) | 1.20066 (15) | 0.0297 (11) | |
C2 | 1.1168 (11) | 0.5309 (6) | 1.23813 (13) | 0.0276 (9) | |
H2A | 1.2901 | 0.5798 | 1.2569 | 0.033* | |
H2B | 0.9447 | 0.4964 | 1.2596 | 0.033* | |
C3 | 1.0199 (11) | 0.6369 (6) | 1.19340 (14) | 0.0250 (10) | |
H3 | 0.8027 | 0.6790 | 1.1942 | 0.030* | |
C4 | 1.2417 (9) | 0.5363 (6) | 1.11851 (13) | 0.0192 (8) | |
H4 | 1.4273 | 0.4611 | 1.1163 | 0.023* | |
C5 | 1.0676 (9) | 0.5213 (6) | 1.06982 (13) | 0.0201 (8) | |
C6 | 1.3526 (11) | 0.7148 (5) | 1.13197 (12) | 0.0218 (9) | |
C7 | 1.5398 (10) | 0.8175 (6) | 1.10754 (14) | 0.0245 (10) | |
H7 | 1.6169 | 0.7752 | 1.0775 | 0.029* | |
C8 | 1.6419 (11) | 0.9914 (5) | 1.12198 (13) | 0.0269 (9) | |
H8A | 1.5056 | 1.0382 | 1.1476 | 0.032* | |
H8B | 1.8551 | 0.9881 | 1.1346 | 0.032* | |
O1 | 1.3545 (10) | 0.2661 (4) | 1.20053 (11) | 0.0458 (9) | |
O2 | 1.1415 (8) | 0.6217 (4) | 1.03630 (9) | 0.0258 (7) | |
O3 | 0.8682 (9) | 0.4058 (4) | 1.06647 (10) | 0.0318 (7) | |
O4 | 1.6262 (9) | 1.0947 (4) | 1.07905 (10) | 0.0321 (8) | |
H4A | 1.6958 | 1.1926 | 1.0851 | 0.038* | |
O5 | 1.2401 (7) | 0.7604 (4) | 1.17783 (9) | 0.0266 (7) | |
N1 | 1.0715 (8) | 0.4860 (5) | 1.16197 (10) | 0.0242 (8) | |
K1 | 0.6334 (2) | 0.52404 (13) | 0.97836 (3) | 0.0284 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.036 (3) | 0.027 (2) | 0.026 (2) | −0.001 (2) | 0.001 (2) | 0.0026 (19) |
C2 | 0.029 (2) | 0.035 (2) | 0.0185 (16) | −0.001 (3) | −0.0026 (18) | 0.0049 (18) |
C3 | 0.026 (2) | 0.025 (2) | 0.024 (2) | 0.0001 (19) | 0.0021 (19) | 0.0033 (18) |
C4 | 0.0183 (18) | 0.018 (2) | 0.0211 (17) | −0.0025 (18) | −0.0009 (15) | 0.0023 (17) |
C5 | 0.017 (2) | 0.022 (2) | 0.0214 (17) | −0.0007 (18) | 0.0031 (15) | −0.0040 (17) |
C6 | 0.020 (2) | 0.028 (2) | 0.0174 (17) | 0.001 (2) | −0.0018 (18) | −0.0019 (16) |
C7 | 0.027 (2) | 0.026 (2) | 0.0204 (18) | −0.0043 (19) | 0.0037 (18) | 0.0005 (17) |
C8 | 0.030 (2) | 0.025 (2) | 0.0255 (18) | −0.003 (2) | −0.002 (2) | 0.0008 (18) |
O1 | 0.070 (3) | 0.033 (2) | 0.0340 (16) | 0.020 (2) | 0.006 (2) | 0.0063 (15) |
O2 | 0.0265 (16) | 0.0296 (17) | 0.0213 (12) | −0.0041 (16) | −0.0002 (13) | 0.0045 (12) |
O3 | 0.0366 (19) | 0.0304 (17) | 0.0285 (14) | −0.0127 (16) | −0.0071 (15) | 0.0038 (13) |
O4 | 0.046 (2) | 0.0201 (15) | 0.0304 (15) | −0.0063 (17) | −0.0020 (17) | 0.0034 (12) |
O5 | 0.0328 (18) | 0.0248 (17) | 0.0221 (13) | −0.0045 (13) | 0.0064 (13) | −0.0013 (13) |
N1 | 0.032 (2) | 0.0236 (19) | 0.0174 (14) | 0.0030 (17) | 0.0036 (14) | 0.0043 (14) |
K1 | 0.0242 (4) | 0.0362 (5) | 0.0248 (4) | 0.0008 (5) | −0.0007 (4) | 0.0031 (4) |
C1—O1 | 1.199 (6) | C7—H7 | 0.9500 |
C1—N1 | 1.408 (5) | C8—O4 | 1.432 (5) |
C1—C2 | 1.525 (6) | C8—H8A | 0.9900 |
C2—C3 | 1.542 (5) | C8—H8B | 0.9900 |
C2—H2A | 0.9900 | O4—H4A | 0.8400 |
C2—H2B | 0.9900 | O2—K1i | 2.773 (3) |
C3—O5 | 1.425 (5) | O2—K1ii | 2.799 (3) |
C3—N1 | 1.480 (5) | O2—K1 | 2.827 (3) |
C3—H3 | 1.0000 | O3—K1 | 2.786 (3) |
C4—N1 | 1.459 (5) | O4—K1ii | 2.818 (4) |
C4—C6 | 1.522 (6) | O4—K1iii | 2.865 (4) |
C4—C5 | 1.542 (5) | O4—H4A | 0.8400 |
C4—H4 | 1.0000 | K1—O2iv | 2.773 (3) |
C5—O2 | 1.252 (5) | K1—O2v | 2.799 (3) |
C5—O3 | 1.256 (5) | K1—O4v | 2.818 (4) |
C6—C7 | 1.325 (6) | K1—O4vi | 2.865 (4) |
C6—O5 | 1.398 (4) | K1—C7v | 3.198 (4) |
C7—C8 | 1.485 (6) | ||
O1—C1—N1 | 130.1 (4) | C1—N1—C4 | 122.4 (4) |
O1—C1—C2 | 136.7 (4) | C1—N1—C3 | 91.1 (3) |
N1—C1—C2 | 93.2 (3) | C4—N1—C3 | 109.9 (3) |
C1—C2—C3 | 84.5 (3) | O2iv—K1—O3 | 82.78 (10) |
C1—C2—H2A | 114.6 | O2iv—K1—O2v | 79.62 (9) |
C3—C2—H2A | 114.6 | O3—K1—O2v | 116.68 (9) |
C1—C2—H2B | 114.6 | O2iv—K1—O4v | 176.73 (10) |
C3—C2—H2B | 114.6 | O3—K1—O4v | 95.70 (10) |
H2A—C2—H2B | 111.7 | O2v—K1—O4v | 103.64 (9) |
O5—C3—N1 | 105.3 (3) | O2iv—K1—O2 | 101.77 (9) |
O5—C3—C2 | 114.9 (4) | O3—K1—O2 | 46.69 (9) |
N1—C3—C2 | 89.7 (3) | O2v—K1—O2 | 78.70 (9) |
O5—C3—H3 | 114.7 | O4v—K1—O2 | 79.11 (9) |
N1—C3—H3 | 114.7 | O2iv—K1—O4vi | 79.21 (9) |
C2—C3—H3 | 114.7 | O3—K1—O4vi | 130.76 (10) |
N1—C4—C6 | 102.0 (3) | O2v—K1—O4vi | 104.54 (9) |
N1—C4—C5 | 116.2 (3) | O4v—K1—O4vi | 99.74 (9) |
C6—C4—C5 | 115.9 (3) | O2—K1—O4vi | 176.76 (10) |
N1—C4—H4 | 107.4 | O2iv—K1—C5 | 90.29 (9) |
C6—C4—H4 | 107.4 | O3—K1—C5 | 23.47 (10) |
C5—C4—H4 | 107.4 | O2v—K1—C5 | 96.56 (11) |
O2—C5—O3 | 125.0 (3) | O4v—K1—C5 | 89.41 (10) |
O2—C5—C4 | 117.7 (4) | O2—K1—C5 | 23.45 (9) |
O3—C5—C4 | 117.2 (3) | O4vi—K1—C5 | 154.16 (10) |
O2—C5—K1 | 64.0 (2) | O2iv—K1—C7v | 137.98 (11) |
O3—C5—K1 | 62.1 (2) | O3—K1—C7v | 124.63 (12) |
C4—C5—K1 | 171.2 (3) | O2v—K1—C7v | 60.23 (10) |
O2—C5—K1i | 44.8 (2) | O4v—K1—C7v | 45.13 (10) |
O3—C5—K1i | 115.7 (3) | O2—K1—C7v | 83.12 (10) |
C4—C5—K1i | 106.1 (2) | O4vi—K1—C7v | 98.25 (10) |
K1—C5—K1i | 81.24 (8) | C5—K1—C7v | 105.17 (11) |
C7—C6—O5 | 121.1 (4) | O2iv—K1—C8vi | 89.53 (10) |
C7—C6—C4 | 128.8 (4) | O3—K1—C8vi | 154.09 (11) |
O5—C6—C4 | 110.0 (3) | O2v—K1—C8vi | 85.89 (9) |
C6—C7—C8 | 127.1 (4) | O4v—K1—C8vi | 90.62 (10) |
C6—C7—K1ii | 105.7 (3) | O2—K1—C8vi | 158.79 (11) |
C8—C7—K1ii | 90.4 (2) | O4vi—K1—C8vi | 23.49 (9) |
C6—C7—H7 | 116.5 | C5—K1—C8vi | 177.48 (12) |
C8—C7—H7 | 116.5 | C7v—K1—C8vi | 76.57 (11) |
K1ii—C7—H7 | 71.9 | O2iv—K1—C5iv | 18.57 (9) |
O4—C8—C7 | 106.4 (3) | O3—K1—C5iv | 68.43 (10) |
O4—C8—K1iii | 52.9 (2) | O2v—K1—C5iv | 96.76 (10) |
C7—C8—K1iii | 86.5 (2) | O4v—K1—C5iv | 158.42 (10) |
O4—C8—K1ii | 49.2 (2) | O2—K1—C5iv | 98.32 (9) |
C7—C8—K1ii | 64.7 (2) | O4vi—K1—C5iv | 81.62 (9) |
K1iii—C8—K1ii | 76.39 (8) | C5—K1—C5iv | 81.24 (8) |
O4—C8—H8A | 110.5 | C7v—K1—C5iv | 156.37 (11) |
C7—C8—H8A | 110.5 | C8vi—K1—C5iv | 97.88 (10) |
K1iii—C8—H8A | 160.2 | O2iv—K1—C8v | 159.90 (10) |
K1ii—C8—H8A | 101.1 | O3—K1—C8v | 115.98 (12) |
O4—C8—H8B | 110.5 | O2v—K1—C8v | 85.05 (9) |
C7—C8—H8B | 110.5 | O4v—K1—C8v | 22.62 (9) |
K1iii—C8—H8B | 72.8 | O2—K1—C8v | 87.75 (10) |
K1ii—C8—H8B | 149.1 | O4vi—K1—C8v | 92.28 (10) |
H8A—C8—H8B | 108.6 | C5—K1—C8v | 104.40 (10) |
C5—O2—K1i | 116.6 (3) | C7v—K1—C8v | 24.83 (10) |
C5—O2—K1ii | 136.3 (3) | C8vi—K1—C8v | 76.39 (8) |
K1i—O2—K1ii | 101.51 (10) | C5iv—K1—C8v | 173.89 (10) |
C5—O2—K1 | 92.6 (2) | O2iv—K1—K1ii | 90.24 (7) |
K1i—O2—K1 | 101.77 (9) | O3—K1—K1ii | 81.25 (7) |
K1ii—O2—K1 | 100.16 (10) | O2v—K1—K1ii | 39.02 (7) |
C5—O3—K1 | 94.5 (2) | O4v—K1—K1ii | 92.38 (7) |
C8—O4—K1ii | 108.2 (2) | O2—K1—K1ii | 39.68 (6) |
C8—O4—K1iii | 103.6 (3) | O4vi—K1—K1ii | 143.56 (7) |
K1ii—O4—K1iii | 99.74 (9) | C5—K1—K1ii | 58.85 (8) |
C8—O4—H4A | 109.5 | C7v—K1—K1ii | 66.94 (8) |
K1ii—O4—H4A | 133.2 | C8vi—K1—K1ii | 123.66 (8) |
K1iii—O4—H4A | 97.3 | C5iv—K1—K1ii | 99.19 (7) |
C6—O5—C3 | 109.4 (3) | C8v—K1—K1ii | 85.90 (8) |
O1—C1—C2—C3 | 168.2 (6) | C5—O2—K1—O3 | −6.0 (2) |
N1—C1—C2—C3 | −9.2 (3) | K1i—O2—K1—O3 | 111.90 (16) |
C1—C2—C3—O5 | −98.0 (4) | K1ii—O2—K1—O3 | −143.96 (16) |
C1—C2—C3—N1 | 8.8 (3) | C5—O2—K1—O2v | 138.9 (2) |
N1—C4—C5—O2 | 151.2 (4) | K1i—O2—K1—O2v | −103.25 (11) |
C6—C4—C5—O2 | 31.4 (5) | K1ii—O2—K1—O2v | 0.89 (9) |
N1—C4—C5—O3 | −30.8 (6) | C5—O2—K1—O4v | −114.7 (3) |
C6—C4—C5—O3 | −150.6 (4) | K1i—O2—K1—O4v | 3.21 (10) |
N1—C4—C5—K1 | 52 (2) | K1ii—O2—K1—O4v | 107.35 (10) |
C6—C4—C5—K1 | −67.5 (19) | C5—O2—K1—O4vi | −45.1 (17) |
N1—C4—C5—K1i | −161.8 (3) | K1i—O2—K1—O4vi | 72.8 (16) |
C6—C4—C5—K1i | 78.4 (4) | K1ii—O2—K1—O4vi | 177 (45) |
N1—C4—C6—C7 | 174.2 (4) | K1i—O2—K1—C5 | 117.9 (3) |
C5—C4—C6—C7 | −58.6 (6) | K1ii—O2—K1—C5 | −138.0 (3) |
N1—C4—C6—O5 | −2.6 (4) | C5—O2—K1—C7v | −160.2 (3) |
C5—C4—C6—O5 | 124.7 (4) | K1i—O2—K1—C7v | −42.33 (11) |
O5—C6—C7—C8 | −3.7 (7) | K1ii—O2—K1—C7v | 61.82 (11) |
C4—C6—C7—C8 | 179.9 (4) | C5—O2—K1—C8vi | −176.9 (3) |
O5—C6—C7—K1ii | −106.5 (4) | K1i—O2—K1—C8vi | −59.1 (3) |
C4—C6—C7—K1ii | 77.1 (5) | K1ii—O2—K1—C8vi | 45.1 (3) |
C6—C7—C8—O4 | −137.0 (5) | C5—O2—K1—C5iv | 43.6 (2) |
K1ii—C7—C8—O4 | −26.9 (3) | K1i—O2—K1—C5iv | 161.47 (10) |
C6—C7—C8—K1iii | 173.3 (5) | K1ii—O2—K1—C5iv | −94.39 (11) |
K1ii—C7—C8—K1iii | −76.57 (10) | C5—O2—K1—C8v | −135.7 (3) |
C6—C7—C8—K1ii | −110.1 (5) | K1i—O2—K1—C8v | −17.85 (11) |
O3—C5—O2—K1i | −92.7 (4) | K1ii—O2—K1—C8v | 86.29 (10) |
C4—C5—O2—K1i | 85.1 (4) | C5—O2—K1—K1ii | 138.0 (3) |
K1—C5—O2—K1i | −104.54 (19) | K1i—O2—K1—K1ii | −104.15 (11) |
O3—C5—O2—K1ii | 119.4 (4) | O2—C5—K1—O2iv | −120.1 (3) |
C4—C5—O2—K1ii | −62.7 (5) | O3—C5—K1—O2iv | 70.9 (3) |
K1—C5—O2—K1ii | 107.6 (3) | C4—C5—K1—O2iv | −16.8 (18) |
K1i—C5—O2—K1ii | −147.8 (5) | K1i—C5—K1—O2iv | −163.73 (9) |
O3—C5—O2—K1 | 11.8 (5) | O2—C5—K1—O3 | 169.1 (4) |
C4—C5—O2—K1 | −170.3 (3) | C4—C5—K1—O3 | −87.6 (18) |
K1i—C5—O2—K1 | 104.54 (19) | K1i—C5—K1—O3 | 125.4 (3) |
O2—C5—O3—K1 | −12.0 (5) | O2—C5—K1—O2v | −40.5 (2) |
C4—C5—O3—K1 | 170.1 (3) | O3—C5—K1—O2v | 150.5 (3) |
K1i—C5—O3—K1 | −63.5 (2) | C4—C5—K1—O2v | 62.8 (18) |
C7—C8—O4—K1ii | 32.7 (4) | K1i—C5—K1—O2v | −84.14 (9) |
K1iii—C8—O4—K1ii | 105.23 (18) | O2—C5—K1—O4v | 63.2 (2) |
C7—C8—O4—K1iii | −72.5 (3) | O3—C5—K1—O4v | −105.9 (3) |
K1ii—C8—O4—K1iii | −105.23 (18) | C4—C5—K1—O4v | 166.5 (18) |
C7—C6—O5—C3 | 173.7 (4) | K1i—C5—K1—O4v | 19.52 (9) |
C4—C6—O5—C3 | −9.2 (4) | O3—C5—K1—O2 | −169.1 (4) |
N1—C3—O5—C6 | 16.9 (4) | C4—C5—K1—O2 | 103.3 (19) |
C2—C3—O5—C6 | 113.9 (4) | K1i—C5—K1—O2 | −43.7 (2) |
O1—C1—N1—C4 | −53.6 (7) | O2—C5—K1—O4vi | 174.7 (2) |
C2—C1—N1—C4 | 124.1 (4) | O3—C5—K1—O4vi | 5.7 (4) |
O1—C1—N1—C3 | −168.1 (6) | C4—C5—K1—O4vi | −82.0 (19) |
C2—C1—N1—C3 | 9.6 (3) | K1i—C5—K1—O4vi | 131.1 (2) |
C6—C4—N1—C1 | −91.7 (5) | O2—C5—K1—C7v | 20.4 (3) |
C5—C4—N1—C1 | 141.3 (4) | O3—C5—K1—C7v | −148.7 (3) |
C6—C4—N1—C3 | 13.0 (4) | C4—C5—K1—C7v | 123.7 (18) |
C5—C4—N1—C3 | −114.0 (4) | K1i—C5—K1—C7v | −23.27 (12) |
O5—C3—N1—C1 | 106.3 (3) | O2—C5—K1—C8vi | 154 (2) |
C2—C3—N1—C1 | −9.5 (3) | O3—C5—K1—C8vi | −15 (2) |
O5—C3—N1—C4 | −18.9 (4) | C4—C5—K1—C8vi | −103 (3) |
C2—C3—N1—C4 | −134.7 (3) | K1i—C5—K1—C8vi | 110 (2) |
C5—O3—K1—O2iv | −107.7 (3) | O2—C5—K1—C5iv | −136.3 (2) |
C5—O3—K1—O2v | −33.2 (3) | O3—C5—K1—C5iv | 54.6 (3) |
C5—O3—K1—O4v | 75.2 (3) | C4—C5—K1—C5iv | −33.0 (19) |
C5—O3—K1—O2 | 6.0 (2) | K1i—C5—K1—C5iv | 180.0 |
C5—O3—K1—O4vi | −176.7 (2) | O2—C5—K1—C8v | 46.1 (3) |
C5—O3—K1—C7v | 37.6 (3) | O3—C5—K1—C8v | −123.0 (3) |
C5—O3—K1—C8vi | 178.5 (2) | C4—C5—K1—C8v | 149.4 (18) |
C5—O3—K1—C5iv | −120.0 (3) | K1i—C5—K1—C8v | 2.41 (12) |
C5—O3—K1—C8v | 64.7 (3) | O2—C5—K1—K1ii | −30.0 (2) |
C5—O3—K1—K1ii | −16.4 (2) | O3—C5—K1—K1ii | 161.0 (3) |
C5—O2—K1—O2iv | 62.1 (3) | C4—C5—K1—K1ii | 73.4 (18) |
K1i—O2—K1—O2iv | 180.0 | K1i—C5—K1—K1ii | −73.62 (7) |
K1ii—O2—K1—O2iv | −75.85 (11) |
Symmetry codes: (i) x+1, y, z; (ii) x+1/2, −y+3/2, −z+2; (iii) x+3/2, −y+3/2, −z+2; (iv) x−1, y, z; (v) x−1/2, −y+3/2, −z+2; (vi) x−3/2, −y+3/2, −z+2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O3vii | 0.84 | 1.90 | 2.673 (5) | 153 |
Symmetry code: (vii) x+1, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | K+·C8H8NO5− |
Mr | 237.25 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 173 |
a, b, c (Å) | 4.3453 (6), 7.8191 (11), 27.491 (3) |
V (Å3) | 934.1 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.57 |
Crystal size (mm) | 0.24 × 0.04 × 0.01 |
Data collection | |
Diffractometer | Rigaku R-AXIS RAPID IP area-detector |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.876, 0.994 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9047, 2138, 1433 |
Rint | 0.088 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.118, 1.12 |
No. of reflections | 2138 |
No. of parameters | 137 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.52, −0.56 |
Absolute structure | Flack (1983), 839 Friedel pairs |
Absolute structure parameter | −0.05 (9) |
Computer programs: PROCESS-AUTO (Rigaku, 1998), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997).
O2—K1i | 2.773 (3) | O3—K1 | 2.786 (3) |
O2—K1ii | 2.799 (3) | O4—K1ii | 2.818 (4) |
O2—K1 | 2.827 (3) | O4—K1iii | 2.865 (4) |
Symmetry codes: (i) x+1, y, z; (ii) x+1/2, −y+3/2, −z+2; (iii) x+3/2, −y+3/2, −z+2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O3iv | 0.840 | 1.898 | 2.673 (5) | 152.75 |
Symmetry code: (iv) x+1, y+1, z. |
Acknowledgements
Grateful thanks are given to the High Directorate of the Education Ministry of Indonesia for a research grant and PT Tempo Scan Pacific Indonesia for the supply of the material. KF was supported by a Grant-in-Aid for JSPS Fellows (Tokyo Institute of Technology G-COE Program: Education and the Research Centre for Emergence of New Molecular Chemistry).
References
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Many pathogenic bacteria secrete β-lactamases as a defense mechanism against β-lactam antibiotics. Because such β-lactamases have the potential to inactivate β-lactam antibiotics, inhibitors for these β-lactamases are clinically very important. Clavulanic acid (CA) is a powerful naturally obtained inhibitor for bacterial β-lactamases produced by the organism Streptomyces clavuligerus. Although CA itself can act as an β-lactam antibiotic and is active against a wide spectrum of Gram-positive and Gram-negative bacteria (Mayer & Deckwer, 1996), it is much more effective as a drug in combination with β-lactamase-sensitive penicillins, such as amoxicillin. In that situation, CA protects the β-lactam ring of the amoxicillin from hydrolysis and can maintain its activity against β-lactamase producing bacteria (Bird et al., 1982). The CA potassium salt is widely used as a drug in injectable and solid form, especially combined with amoxicillin sodium and amoxicillin trihydrate (Navarro, 2005).
In this context, an understanding of the structure of CA is important in order to establish its ability to form molecular interactions. Unfortunately, CA is chemically unstable as are the other β-lactam antibiotics, being very sensitive to pH, temperature, and humidity via the hydrolysis degradation mechanism; (Bersanetti et al., 2005; Hickey et al., 2007; Saudagar et al., 2008). The decomposition is also self-catalyzed (Brethauer et al. 2008; Haginaka et al. 1985) and there have been some difficulties in obtaining a single crystals of CA. Therefore, until now there has been no report of a crystal structure of CA. In this study, single crystals of potassium clavulanate were successfully obtained by a low-temperature crystallization process and the crystal structure was determined.
In the molecular structure of potassium clavulanate, Fig. 1, the C5–O2 and C5–O3 distances of 1.262 (5)Å and 1.256 (5) Å, respectively, indicate that the negative charge of the carboxylate group is delocalised. The potassium cation is surrounded by six oxygen atoms, three O2, one O3 and two O4, deriv ed from four different clavulanate anions. The selected bond lengths around the potassium cation are listed in Table 1. These interactions are infinitely linked along the a axis and lead to an ionic (hydrophilic) column structure. These columns are connected by intermolecular O–H···O hydrogen bonds formed between O4-hydroxyl groups and carboxylate-O2 atoms, and form a hydrophobic layer in the ab plane; Fig. 2. By contrast, the remaining hydrophobic groups (i.e. bicyclo groups) form a hydrophobic layer so that the crystal structure comprises alternating hydrophilic and hydrophilic regions.