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The title compound, C17H22O6, has an exocyclic ester group at the hexopyranosyl sugar residue. The carbonyl group shows a conformation that is eclipsed with respect to the adjacent ring C—H bond. The two ester torsion angles are denoted by syn and cis conformations. One of these torsion angles is indicated to have a similar conformation in solution, as analyzed by NMR spectroscopy and a Karplus-type relationship.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106021603/av3012sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106021603/av3012Isup2.hkl
Contains datablock I

CCDC reference: 618613

Comment top

The title compound, (I), is an intermediate in the synthesis of rhamnopyranosyl oligosaccharides. The crystal structure of (I) is similar to that of another rhamnose derivative published some time ago (Eriksson et al., 1999). In the light of recent conformational analysis of acetyl esters of cyclic alcohols based on molecular mechanics calculations, NMR criteria and crystal structures (González-Outeiriño et al., 2005), it was of interest to analyze the conformation of the ester group in (I).

In the study by González-Outeiriño et al. (2005), it was concluded that acetyl ester groups without flanking equatorial groups prefer a staggered conformation, whereas when two flanking equatorial substituents were present an eclipsed conformation was preferred. For the θ1 torsion angle, corresponding to H4—C4—O4—C10 in (I), the syn conformation is the one that is usually observed, since the anti conformation was calculated to be at least 8 kJ mol−1 higher in energy. For the θ2 torsion angle, corresponding to C4—O4—C10—O10 in (I), analysis of the crystal structures revealed almost exclusive preference for a cis conformation, with only a few cases having a trans (anti-periplanar) conformation. Furthermore, a Karplus-type relationship was derived for use with NMR data, viz. 3JC,H = 3.1 cos2θ − 1.25 cosθ + 2.35 (Anderson, 2005).

For (I), the torsion angles are θ1 = −14.2° and θ2 = −7.7 (2)°. Thus, the conformation at the ester group can be described as eclipsed according to González-Outeiriño et al. (2005), with θ1 as syn and θ2 as cis.

To investigate the conformational preference of the θ1 torsion angle of the monosaccharide in solution, the 1H and 13C chemical shifts, as well as selected 3JH,H coupling constants, were determined by one- and two-dimensional NMR spectroscopy (Table 3). Heteronuclear 3JC,H coupling constants can be determined using an NMR technique based on selective excitation of 13C resonances and detection of the anti-phase multiplet pattern in the 1H NMR spectrum, using band-selective proton decoupling during the acquisition period if necessary (Nishida et al., 1996). Analysis of the NMR spectrum obtained with band-selective proton decoupling of the H5 resonance revealed JH4,C10 = 4.0 Hz. Employing the Karplus-type relationship, |θ1| = 17°, if interpreted as a single syn conformer. The θ1 torsion angle in (I) is therefore anticipated to have a similar conformation in solution to that in the crystal.

A few weak intermolecular hydrogen bonds are listed in Table 2. The phenyl rings are oriented in a pattern resembling the well known herringbone pattern (Desiraju & Steiner, 1999), as shown in Fig. 2, although it appears that close C—H···π contacts are absent in the title compound. The hexapyranose ring is somewhat distorted from a regular 1C4 chair conformation, with puckering parameters (Cremer & Pople, 1975) q2 = 0.226 (2) Å, q3 = −0.489 (2) Å, ϕ2 = 122.2 (4)°, Q = 0.538 (2) Å and θ = 155.2 (2) Å. The five-membered ring has an envelope conformation on C2, with puckering parameters q2 = 0.353 (2) Å and ϕ2 = 28.5 (2)°.

Experimental top

The synthesis of (I) was performed starting from L-rhamnose using the methodology described by Rainer et al. (1992) and Norberg et al. (1986). Compound (I) has previously been prepared via a different route (Byramova et al., 1985). The synthesis product was analyzed with MALDI-MS: [M+Na]+ m/z, calculated for C17H22NaO6: 345.13; found: 345.26. 1H and 13C NMR data of (I) referenced to internal TMS (δ = 0.0) in CDCl3 solution at 298 K were assigned by one- and two-dimensional NMR spectroscopy techniques using a Varian Inova spectrometer operating at a proton frequency of 600 MHz. The monosaccharide was dissolved in hot ethanol and an excess of n-pentane was added at ambient temperature. Crystals for X-ray crystallographic analysis were formed at 253 K. The scattering power of the crystals was weak. Thus, it was decided to collect data with synchrotron radiation on beamline I711 at the Swedish synchrotron radiation facility, MAXLAB, Lund, Sweden.

Refinement top

H atoms were positioned geometrically and allowed to ride on their parent atoms, with CH, CH3 and aromatic C—H bonds of 1.00, 0.98 and 0.95 Å, respectively, and with Uiso(H) = Ueq(C), or 1.5Ueq(C) for methyl H. [Please check added text] The Flack parameter (Flack, 1983) derived from the refinement using unmerged data [x = 0.43 (15)] was inconclusive. Thus, the reflection data were merged in the final refinement. The absolute configuration was set by the a priori knowledge of the absolute configuration of the synthesis components.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids and the atom-numbering scheme. H atoms are shown as small spheres of arbitrary radii. The torsion angles θ1 (H4—C4—O4—C10) and θ2 (C4—O4—C10—O10) are shown.
[Figure 2] Fig. 2. A packing diagram, viewed along the b axis, showing one half of the unit-cell content in the b direction. Note the herringbone pattern (Desiraju & Steiner, 1999) for the packing of the benzene rings. The C9—H9B···Cg interaction is shown with a dotted line (Cg is the centroid of the benzene ring).
Methyl 4-O-benzoyl-2,3-O-isopropylidene-α-L-rhamnopyranoside top
Crystal data top
C17H22O6F(000) = 688
Mr = 322.35Dx = 1.282 Mg m3
Orthorhombic, P212121Synchrotron radiation, λ = 1.350 Å
Hall symbol: P 2ac 2abCell parameters from 999 reflections
a = 9.720 (8) Åθ = 3.0–29.0°
b = 10.654 (11) ŵ = 0.52 mm1
c = 16.127 (14) ÅT = 100 K
V = 1670 (3) Å3Prism, colourless
Z = 40.15 × 0.10 × 0.08 mm
Data collection top
Bruker SMART 1K area-detector
diffractometer
2244 independent reflections
Radiation source: Beamline I711, Maxlab, Lund, Sweden2133 reflections with I > 2σ(I)
Silicon monochromatorRint = 0.095
Detector resolution: 10 pixels mm-1θmax = 63.4°, θmin = 4.4°
ω scan at different ϕ and 2θh = 1212
Absorption correction: part of the refinement model (ΔF)
(SADABS; Sheldrick, 2002)
k = 1312
Tmin = 0.98, Tmax = 1.00l = 2120
18820 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.033Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.088H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.0492P)2 + 0.241P]
where P = (Fo2 + 2Fc2)/3
2244 reflections(Δ/σ)max < 0.001
212 parametersΔρmax = 0.26 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C17H22O6V = 1670 (3) Å3
Mr = 322.35Z = 4
Orthorhombic, P212121Synchrotron radiation, λ = 1.350 Å
a = 9.720 (8) ŵ = 0.52 mm1
b = 10.654 (11) ÅT = 100 K
c = 16.127 (14) Å0.15 × 0.10 × 0.08 mm
Data collection top
Bruker SMART 1K area-detector
diffractometer
2244 independent reflections
Absorption correction: part of the refinement model (ΔF)
(SADABS; Sheldrick, 2002)
2133 reflections with I > 2σ(I)
Tmin = 0.98, Tmax = 1.00Rint = 0.095
18820 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0330 restraints
wR(F2) = 0.088H-atom parameters constrained
S = 1.08Δρmax = 0.26 e Å3
2244 reflectionsΔρmin = 0.21 e Å3
212 parameters
Special details top

Experimental. Absolute structure known from synthesis.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.40567 (16)0.16439 (16)0.43467 (10)0.0149 (3)
H10.33190.11550.46340.015*
C20.34421 (15)0.22351 (16)0.35718 (9)0.0139 (3)
H20.29110.30050.37240.014*
C30.44466 (16)0.25333 (15)0.28705 (9)0.0152 (3)
H30.48050.34080.29320.015*
C40.56396 (16)0.16052 (15)0.28293 (10)0.0149 (3)
H40.53150.07910.25910.015*
C50.62472 (16)0.13851 (16)0.36931 (10)0.0166 (3)
H50.65380.22010.39450.017*
C60.74363 (18)0.04612 (18)0.36988 (11)0.0223 (3)
H6A0.78040.03910.42630.022*
H6B0.81610.07590.33250.022*
H6C0.71110.03630.35120.022*
C70.23802 (17)0.17501 (17)0.23437 (10)0.0180 (3)
C80.2254 (2)0.0600 (2)0.17966 (11)0.0302 (4)
H8A0.14220.01330.19470.030*
H8B0.30620.00630.18740.030*
H8C0.21970.08610.12150.030*
C90.11593 (17)0.26332 (19)0.22673 (11)0.0238 (4)
H9A0.03110.21790.24010.024*
H9B0.11060.29540.16990.024*
H9C0.12740.33360.26530.024*
C100.72022 (16)0.14471 (16)0.16789 (10)0.0150 (3)
C110.80582 (15)0.21873 (16)0.10960 (9)0.0137 (3)
C120.87984 (18)0.15474 (17)0.04875 (10)0.0191 (3)
H120.87500.06580.04580.019*
C130.96073 (19)0.22041 (19)0.00766 (11)0.0245 (4)
H131.01080.17660.04920.024*
C140.96792 (19)0.35107 (18)0.00285 (11)0.0229 (4)
H141.02360.39640.04090.023*
C150.89381 (17)0.41507 (17)0.05756 (11)0.0194 (3)
H150.89900.50400.06050.019*
C160.81219 (16)0.34999 (16)0.11373 (10)0.0155 (3)
H160.76110.39410.15460.016*
C170.4911 (2)0.22159 (18)0.56583 (10)0.0235 (4)
H17A0.51800.29370.59990.035*
H17B0.57040.16580.55850.035*
H17C0.41660.17570.59340.035*
O10.44505 (12)0.26463 (11)0.48656 (7)0.0177 (2)
O20.25509 (12)0.13414 (11)0.31830 (7)0.0165 (2)
O30.36144 (12)0.24391 (12)0.21417 (7)0.0193 (3)
O40.66485 (11)0.21687 (12)0.22819 (7)0.0167 (2)
O50.51651 (11)0.08257 (11)0.41771 (7)0.0165 (2)
O100.70053 (14)0.03238 (12)0.16229 (8)0.0227 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0159 (7)0.0132 (7)0.0157 (7)0.0003 (6)0.0006 (5)0.0003 (6)
C20.0147 (7)0.0116 (7)0.0154 (7)0.0007 (6)0.0003 (5)0.0024 (5)
C30.0160 (7)0.0129 (8)0.0168 (7)0.0005 (6)0.0004 (5)0.0025 (5)
C40.0154 (6)0.0109 (7)0.0184 (7)0.0011 (6)0.0024 (6)0.0012 (6)
C50.0161 (7)0.0147 (8)0.0189 (7)0.0005 (6)0.0003 (6)0.0008 (6)
C60.0206 (8)0.0210 (9)0.0254 (8)0.0047 (7)0.0029 (6)0.0000 (7)
C70.0193 (7)0.0191 (8)0.0156 (7)0.0033 (7)0.0018 (6)0.0039 (6)
C80.0413 (11)0.0278 (10)0.0215 (8)0.0051 (8)0.0038 (7)0.0048 (7)
C90.0172 (7)0.0312 (10)0.0231 (8)0.0011 (7)0.0047 (6)0.0077 (7)
C100.0159 (7)0.0127 (8)0.0164 (7)0.0003 (5)0.0019 (5)0.0010 (6)
C110.0125 (6)0.0135 (7)0.0150 (7)0.0006 (6)0.0007 (5)0.0011 (6)
C120.0231 (8)0.0146 (8)0.0197 (7)0.0012 (6)0.0012 (6)0.0037 (6)
C130.0273 (8)0.0243 (9)0.0218 (8)0.0022 (7)0.0079 (7)0.0047 (7)
C140.0230 (8)0.0233 (10)0.0226 (8)0.0013 (7)0.0052 (6)0.0031 (7)
C150.0201 (7)0.0138 (8)0.0245 (8)0.0002 (6)0.0014 (6)0.0009 (6)
C160.0148 (7)0.0123 (8)0.0194 (7)0.0004 (6)0.0002 (6)0.0015 (6)
C170.0312 (9)0.0218 (9)0.0175 (8)0.0000 (7)0.0065 (7)0.0006 (7)
O10.0242 (6)0.0139 (6)0.0151 (5)0.0005 (5)0.0020 (4)0.0002 (4)
O20.0194 (6)0.0154 (6)0.0147 (5)0.0042 (5)0.0021 (4)0.0035 (4)
O30.0181 (5)0.0243 (7)0.0154 (5)0.0007 (5)0.0002 (4)0.0063 (5)
O40.0180 (5)0.0115 (6)0.0205 (5)0.0028 (4)0.0054 (4)0.0022 (4)
O50.0189 (5)0.0110 (5)0.0195 (5)0.0014 (4)0.0009 (4)0.0025 (4)
O100.0342 (7)0.0103 (6)0.0235 (6)0.0024 (5)0.0047 (5)0.0017 (5)
Geometric parameters (Å, º) top
C1—O11.410 (2)C8—H8B0.9800
C1—O51.413 (2)C8—H8C0.9800
C1—C21.522 (2)C9—H9A0.9800
C1—H11.0000C9—H9B0.9800
C2—O21.432 (2)C9—H9C0.9800
C2—C31.527 (2)C10—O101.215 (3)
C2—H21.0000C10—O41.352 (2)
C3—O31.430 (2)C10—C111.482 (2)
C3—C41.525 (2)C11—C121.395 (2)
C3—H31.0000C11—C161.401 (3)
C4—O41.449 (2)C12—C131.391 (3)
C4—C51.531 (2)C12—H120.9500
C4—H41.0000C13—C141.396 (3)
C5—O51.439 (2)C13—H130.9500
C5—C61.518 (2)C14—C151.390 (2)
C5—H51.0000C14—H140.9500
C6—H6A0.9800C15—C161.390 (2)
C6—H6B0.9800C15—H150.9500
C6—H6C0.9800C16—H160.9500
C7—O21.432 (2)C17—O11.430 (2)
C7—O31.444 (2)C17—H17A0.9800
C7—C81.515 (3)C17—H17B0.9800
C7—C91.520 (3)C17—H17C0.9800
C8—H8A0.9800
O1—C1—O5112.05 (13)C7—C8—H8B109.5
O1—C1—C2106.29 (14)H8A—C8—H8B109.5
O5—C1—C2113.32 (13)C7—C8—H8C109.5
O1—C1—H1108.3H8A—C8—H8C109.5
O5—C1—H1108.3H8B—C8—H8C109.5
C2—C1—H1108.3C7—C9—H9A109.5
O2—C2—C1108.77 (14)C7—C9—H9B109.5
O2—C2—C3101.59 (13)H9A—C9—H9B109.5
C1—C2—C3116.31 (13)C7—C9—H9C109.5
O2—C2—H2109.9H9A—C9—H9C109.5
C1—C2—H2109.9H9B—C9—H9C109.5
C3—C2—H2109.9O10—C10—O4123.43 (16)
O3—C3—C4110.40 (13)O10—C10—C11124.41 (16)
O3—C3—C2103.43 (13)O4—C10—C11112.16 (15)
C4—C3—C2112.55 (13)C12—C11—C16119.89 (16)
O3—C3—H3110.1C12—C11—C10118.40 (16)
C4—C3—H3110.1C16—C11—C10121.70 (15)
C2—C3—H3110.1C13—C12—C11120.39 (17)
O4—C4—C3105.81 (13)C13—C12—H12119.8
O4—C4—C5110.89 (13)C11—C12—H12119.8
C3—C4—C5110.66 (13)C12—C13—C14119.56 (17)
O4—C4—H4109.8C12—C13—H13120.2
C3—C4—H4109.8C14—C13—H13120.2
C5—C4—H4109.8C15—C14—C13120.14 (17)
O5—C5—C6106.53 (14)C15—C14—H14119.9
O5—C5—C4105.96 (13)C13—C14—H14119.9
C6—C5—C4113.48 (13)C16—C15—C14120.52 (18)
O5—C5—H5110.2C16—C15—H15119.7
C6—C5—H5110.2C14—C15—H15119.7
C4—C5—H5110.2C15—C16—C11119.48 (16)
C5—C6—H6A109.5C15—C16—H16120.3
C5—C6—H6B109.5C11—C16—H16120.3
H6A—C6—H6B109.5O1—C17—H17A109.5
C5—C6—H6C109.5O1—C17—H17B109.5
H6A—C6—H6C109.5H17A—C17—H17B109.5
H6B—C6—H6C109.5O1—C17—H17C109.5
O2—C7—O3105.76 (13)H17A—C17—H17C109.5
O2—C7—C8108.31 (15)H17B—C17—H17C109.5
O3—C7—C8110.31 (15)C1—O1—C17111.89 (14)
O2—C7—C9110.83 (14)C7—O2—C2106.37 (13)
O3—C7—C9108.42 (15)C3—O3—C7108.68 (12)
C8—C7—C9112.97 (16)C10—O4—C4118.16 (14)
C7—C8—H8A109.5C1—O5—C5114.01 (13)
O1—C1—C2—O2157.19 (12)C14—C15—C16—C110.5 (2)
O5—C1—C2—O279.32 (16)C12—C11—C16—C150.8 (2)
O1—C1—C2—C388.94 (16)C10—C11—C16—C15179.90 (14)
O5—C1—C2—C334.55 (19)O5—C1—O1—C1762.01 (17)
O2—C2—C3—O333.42 (15)C2—C1—O1—C17173.71 (13)
C1—C2—C3—O3151.32 (14)O3—C7—O2—C227.55 (16)
O2—C2—C3—C485.74 (16)C8—C7—O2—C2145.80 (14)
C1—C2—C3—C432.16 (19)C9—C7—O2—C289.75 (17)
O3—C3—C4—O478.25 (16)C1—C2—O2—C7160.68 (13)
C2—C3—C4—O4166.74 (12)C3—C2—O2—C737.48 (15)
O3—C3—C4—C5161.57 (13)C4—C3—O3—C7103.04 (16)
C2—C3—C4—C546.56 (18)C2—C3—O3—C717.59 (16)
O4—C4—C5—O5179.86 (12)O2—C7—O3—C35.03 (17)
C3—C4—C5—O563.04 (17)C8—C7—O3—C3121.94 (16)
O4—C4—C5—C663.31 (19)C9—C7—O3—C3113.87 (15)
C3—C4—C5—C6179.59 (13)O10—C10—O4—C47.7 (2)
O10—C10—C11—C126.5 (2)C11—C10—O4—C4171.77 (12)
O4—C10—C11—C12174.09 (13)C3—C4—O4—C10132.61 (14)
O10—C10—C11—C16172.67 (16)C5—C4—O4—C10107.36 (16)
O4—C10—C11—C166.8 (2)O1—C1—O5—C566.10 (17)
C16—C11—C12—C130.4 (2)C2—C1—O5—C554.17 (17)
C10—C11—C12—C13179.53 (15)C6—C5—O5—C1170.53 (13)
C11—C12—C13—C140.3 (3)C4—C5—O5—C168.33 (16)
C12—C13—C14—C150.5 (3)O10—C10—O4—C47.7 (2)
C13—C14—C15—C160.1 (3)C10—O4—C4—H414.2
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O10i1.002.533.334 (4)137
C16—H16···O2i0.952.603.285 (4)129
C9—H9B···Cgii0.982.883.585 (4)130
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x1, y, z.

Experimental details

Crystal data
Chemical formulaC17H22O6
Mr322.35
Crystal system, space groupOrthorhombic, P212121
Temperature (K)100
a, b, c (Å)9.720 (8), 10.654 (11), 16.127 (14)
V3)1670 (3)
Z4
Radiation typeSynchrotron, λ = 1.350 Å
µ (mm1)0.52
Crystal size (mm)0.15 × 0.10 × 0.08
Data collection
DiffractometerBruker SMART 1K area-detector
diffractometer
Absorption correctionPart of the refinement model (ΔF)
(SADABS; Sheldrick, 2002)
Tmin, Tmax0.98, 1.00
No. of measured, independent and
observed [I > 2σ(I)] reflections
18820, 2244, 2133
Rint0.095
(sin θ/λ)max1)0.662
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.033, 0.088, 1.08
No. of reflections2244
No. of parameters212
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.26, 0.21

Computer programs: SMART (Bruker, 1998), SMART, SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Bergerhoff, 1996), PLATON (Spek, 2003).

Selected torsion angles (º) top
O5—C1—C2—C334.55 (19)C2—C1—O5—C554.17 (17)
C1—C2—C3—C432.16 (19)C4—C5—O5—C168.33 (16)
C2—C3—C4—C546.56 (18)O10—C10—O4—C47.7 (2)
C3—C4—C5—O563.04 (17)C10—O4—C4—H414.2
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O10i1.002.533.334 (4)137
C16—H16···O2i0.952.603.285 (4)129
C9—H9B···Cgii0.982.883.585 (4)130
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x1, y, z.
1H and 13C NMR chemical shifts of compound (I) in CDCl3 solution at 298 K. Selected 3JH,H are given in parentheses. top
H atomδH 3JH,H+1C atomδC
H14.95(0.8)C198.2
H24.19(5.5)C276.1
H34.33(7.8)C375.9
H45.12(10.1)C475.1
H53.87(6.2)C564.0
H61.23C617.2
C7109.8
H81.62C827.8
H91.35C926.4
C10165.8
C11129.9
H12,H168.05C12,C16129.8
H13,H157.44C13,C15128.4
H147.56C14133.2
H173.42C1755.0
 

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