organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

Methyl 4,6-O-benzyl­­idene-α-D-gluco­pyran­oside monohydrate

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aNelson Mandela University, Summerstrand Campus, Department of Chemistry, University Way, Summerstrand, PO Box 77000, Port Elizabeth, 6031, South Africa
*Correspondence e-mail: [email protected]

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 24 October 2025; accepted 28 October 2025; online 6 November 2025)

The title compound, C14H18O6·H2O, is a partially protected derivative of D-gluco­pyran­ose. The asymmetric unit contains one sugar molecule and one water molecule of crystallization. Classical hydrogen bonds of the O—H⋯O type form a cooperative set and are observed next to a C—H⋯O(water) contact, connecting the entities of the asymmetric unit into a three-dimensional network.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Carbohydrates are an important group of biomolecules and form part of the three macronutrients of the human diet. Natural members of this compound class of polyhy­droxy­carbonyls abound for derivatives with five and six carbon atoms, whose stereochemical diversity is enriched by the ability to form furan­oid and pyran­oid intra­molecular hemiacetal-type addition compounds. As they are the product of natural photosynthesis, they are debated as renewable and carbon-neutral feedstock materials for many industrial processes; however, precisely because of their stereochemical variability, exploiting their synthetic potential often requires a carefully crafted preparative strategy based on protection group chemistry (Lindhorst, 2003View full citation).

In connection with the synthesis of coordination compounds, limiting the number of potential donor sites on a polyfunctional carbohydrate is an important measure to ensure the formation of well-defined product species. In connection with a research project around the coordination behaviour of certain hexoses, partially protected derivatives of D-glucose were to be investigated with a specific focus on the trans-orientated hydroxyl groups on the six-membered ring. To this end, methyl-4,6-O-benzyl­idene-α-D-gluco­pyran­oside was synthesized and characterized in the solid state to allow for the comparison of metrical parameters in the free ligand and in coordination compounds. The structure of the title compound has been reported earlier (Tamaru et al., 2001View full citation) but no three-dimensional coordinates were deposited. However, structural information is at hand for the anhydrous version of the title compound (Luboradzki et al., 2000View full citation) as well as the β-anomer of the carbohydrate (Jessen et al., 2001View full citation). The stereoisomeric altro­pyran­oside (Bozo & Vasella, 1992View full citation), allo­pyran­oside (Muddasani et al., 1994View full citation) and ido­pyran­oside (Chu & Jeffrey, 1965View full citation; Liu et al., 1993View full citation; Orban et al., 2023View full citation) equivalents of the title compound have been the focus of diffraction studies on single crystals previously. The present study is a continuation of our inter­est in structural aspects of coordination compounds of carbohydrate derivatives (Betz & Klüfers, 2007aView full citation, 2009View full citation; Betz et al., 2007aView full citation) as well as polyheterocyclic compounds (Muller et al., 2021View full citation; Betz & Klüfers, 2007bView full citation,cView full citation,dView full citation; Betz & Klüfers, 2008aView full citation,bView full citation; Betz et al., 2007bView full citation) and intends to close the gap of missing three-dimensional coordinates for the title compound.

The title compound (Fig. 1[link]) is a twofold protected derivative of D-gluco­pyran­ose with the anomeric hydroxyl group converted into a meth­oxy group (O6–C8) and the hy­droxy­methyl and the adjacent ring-bound hydroxyl group capped by a benzyl­idene protection group. The two trans-orientated hydroxyl groups on the pyran­ose ring remain free. A mol­ecule of water is present in the asymmetric unit. Bond lengths and angles are in good agreement with values reported for comparable compounds whose metrical parameters have been elucidated by means of diffraction studies on single crystals and deposited with the Cambridge Structural Database (Groom et al., 2016View full citation). While the meth­oxy group occupies an axial position, the phenyl group is found in an equatorial position. The two free hydroxyl groups adopt a staggered conformation with a O4—C3—C4—O5 torsion angle of 65.17 (16)°. A conformational analysis of the six-membered rings according to Cremer & Pople (1975View full citation) shows the pyran­oid ring to adopt a 1C4 (O2CC3) conformation while the six-membered ring established by the condensed benzyl­idene protection group is present in a 4C1 (C7CO1) conformation (Boeyens, 1978View full citation).

[Figure 1]
Figure 1
The mol­ecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at the 50% probability level).

In the crystal, classical hydrogen bonds of the O—H⋯O type are observed next to a C—H⋯O(water) contact (Table 1[link]) whose range falls by more than 0.1 Å below the sum of van der Waals radii of the atoms participating in them. The hydroxyl group adjacent to the anomeric center establishes a hydrogen bond to the oxygen atom of the meth­oxy group as acceptor, while the second free hydroxyl group involves the oxygen atom of the free water mol­ecule as acceptor. The water mol­ecule exclusively forms hydrogen bonds to the oxygen atom of the second free hydroxyl group, thus giving rise to a cooperative set of hydrogen bonds. The C—H⋯O(water) contact is observed between one of the hydrogen atoms of the meth­oxy group as donor and solvent mol­ecule's oxygen atom as acceptor. A second C—H⋯O contact between the hydrogen atom of the anomeric center's methine group and the oxygen atom of the hydroxyl group adjacent to the anomeric center is listed for completeness but could be considered an artefact (or consequence) of the hydrogen bonds established by the neighbouring hydroxyl group resulting in distance shortening between the respective C—H and O motifs involved. In terms of graph-set analysis (Etter et al., 1990View full citation; Bernstein et al., 1995View full citation), the classical hydrogen bonds require a DDDC11(5) descriptor on the unary level while the C—H⋯O contacts require a DC11(4) descriptor on the same level with the finite pattern reserved for the water-based contact. Furthermore, one C—H⋯π contact is apparent in between the hydrogen atom of the benzyl­idene protection group and the aromatic system that connects the mol­ecules to chains along the crystallographic b axis. π-Stacking is not a stabilizing factor in the crystal structure of the title compound with the shortest distance in between two centers of gravity measured at 4.8475 (13) Å, which is in agreement with the length of the b axis of the unit cell (Fig. 2[link]).

Table 1
Hydrogen-bond geometry (Å, °)

Cg(1) is the centroid of carbon atoms C21–C26.

D—H⋯A D—H H⋯A DA D—H⋯A
O4—H4A⋯O7 0.84 1.86 2.6925 (19) 172
O5—H5A⋯O5i 0.84 2.48 3.1906 (18) 143
O5—H5A⋯O6i 0.84 2.12 2.8486 (18) 145
O7—H7C⋯O4ii 0.84 (1) 2.08 (2) 2.8758 (17) 159 (3)
O7—H7D⋯O4iii 0.83 (1) 2.02 (1) 2.8444 (19) 175 (3)
C5—H5⋯O5i 1.00 2.46 3.299 (2) 141
C8—H8C⋯O7iv 0.98 2.43 3.380 (3) 163
C1—H1⋯Cg(1)v 1.00 2.56 3.516 (2) 161
Symmetry codes: (i) Mathematical equation; (ii) Mathematical equation; (iii) Mathematical equation; (iv) Mathematical equation; (v) Mathematical equation.
[Figure 2]
Figure 2
Selected inter­molecular contacts, viewed along [010].

Synthesis and crystallization

The compound was obtained following published standard procedures (Becker et al., 2000View full citation; Lindhorst, 2003View full citation; Evans, 1972View full citation). Crystals suitable for the diffraction study were obtained upon recrystallization from boiling propan-2-ol containing water (alcohol:water approximately 95:5).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C14H18O6·H2O
Mr 300.30
Crystal system, space group Monoclinic, P21
Temperature (K) 200
a, b, c (Å) 8.9794 (6), 4.8475 (3), 17.3824 (11)
β (°) 103.927 (2)
V3) 734.37 (8)
Z 2
Radiation type Mo Kα
μ (mm−1) 0.11
Crystal size (mm) 0.50 × 0.13 × 0.07
 
Data collection
Diffractometer Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Krause et al., 2015View full citation)
Tmin, Tmax 0.705, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 41341, 3652, 3442
Rint 0.033
(sin θ/λ)max−1) 0.667
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.081, 1.06
No. of reflections 3652
No. of parameters 204
No. of restraints 4
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.25, −0.16
Absolute structure Flack x determined using 1467 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013View full citation)
Absolute structure parameter −0.17 (16)
Computer programs: APEX2 and SAINT (Bruker, 2014View full citation), SHELXS97 (Sheldrick 2008View full citation), ORTEP-3 for Windows (Farrugia, 2012View full citation), Mercury (Macrae et al., 2020View full citation), SHELXL2019/3 (Sheldrick, 2015View full citation) and PLATON (Spek, 2020View full citation).

Structural data


Computing details top

Methyl 4,6-O-benzylidene-α-D-glucopyranoside monohydrate top
Crystal data top
C14H18O6·H2OF(000) = 320
Mr = 300.30Dx = 1.358 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
a = 8.9794 (6) ÅCell parameters from 9923 reflections
b = 4.8475 (3) Åθ = 2.4–28.3°
c = 17.3824 (11) ŵ = 0.11 mm1
β = 103.927 (2)°T = 200 K
V = 734.37 (8) Å3Rod, colourless
Z = 20.50 × 0.13 × 0.07 mm
Data collection top
Bruker APEXII CCD
diffractometer
3652 independent reflections
Radiation source: sealed tube3442 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.033
φ and ω scansθmax = 28.3°, θmin = 2.3°
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)
h = 1111
Tmin = 0.705, Tmax = 0.746k = 66
41341 measured reflectionsl = 2323
Refinement top
Refinement on F2Hydrogen site location: mixed
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.030 w = 1/[σ2(Fo2) + (0.0395P)2 + 0.1456P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.081(Δ/σ)max < 0.001
S = 1.06Δρmax = 0.25 e Å3
3652 reflectionsΔρmin = 0.16 e Å3
204 parametersExtinction correction: SHELXL-2019/2 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
4 restraintsExtinction coefficient: 0.019 (5)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack x determined using 1467 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.17 (16)
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. The carbon-bound H atoms were placed in calculated positions (C–H 0.98 Å for the methyl group, C–H 0.99 Å for the methylene group and C–H 1.00 Å for the methine groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2Ueq(C).

The H atoms of the methyl group were allowed to rotate with a fixed angle around the C–O bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2015), with U(H) set to 1.5Ueq(C).

The H atoms of the hydroxyl groups were allowed to rotate with a fixed angle around the C–O bond to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2015)), with U(H) set to 1.5Ueq(O).

The hydrogen atoms of the water molecule were located on a difference Fourier map and refined freely with the O—H bonds restrained to 0.84 (1) Å and the H···H distance restrained to 1.34 (2) Å.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.46554 (13)0.5554 (2)0.74863 (6)0.0238 (3)
O20.12794 (13)0.9982 (3)0.71868 (7)0.0254 (3)
O30.40114 (14)0.6184 (3)0.87039 (7)0.0314 (3)
O40.42598 (14)0.7276 (3)0.58470 (7)0.0276 (3)
H4A0.4711730.5747770.5881480.044 (7)*
O50.11857 (16)0.8527 (3)0.50945 (7)0.0326 (3)
H5A0.0730920.9895900.4848810.043 (7)*
O60.02371 (13)0.7058 (3)0.62439 (7)0.0297 (3)
O70.57272 (16)0.2455 (3)0.58050 (8)0.0348 (3)
C10.52160 (18)0.6135 (4)0.83089 (9)0.0244 (3)
H10.5741340.7968580.8371460.029*
C20.36312 (17)0.7704 (3)0.71266 (9)0.0206 (3)
H20.4185780.9509730.7202240.025*
C30.30499 (17)0.7132 (3)0.62492 (9)0.0206 (3)
H30.2576450.5253720.6174320.025*
C40.18457 (19)0.9274 (3)0.58932 (9)0.0233 (3)
H40.2362111.1103640.5898840.028*
C50.06150 (19)0.9515 (3)0.63686 (10)0.0244 (3)
H50.0079311.1092560.6155020.029*
C60.23033 (18)0.7808 (3)0.75229 (9)0.0233 (3)
H60.1743210.6007240.7446130.028*
C70.2933 (2)0.8339 (4)0.84008 (10)0.0312 (4)
H7A0.3446311.0159080.8483620.037*
H7B0.2089700.8329900.8677830.037*
C80.1524 (2)0.7112 (6)0.65891 (16)0.0531 (6)
H8A0.2133560.8773480.6414020.080*
H8B0.1165550.7128090.7168010.080*
H8C0.2158180.5472680.6422670.080*
C210.63591 (19)0.3933 (4)0.86650 (10)0.0259 (3)
C220.7440 (2)0.3128 (5)0.82542 (12)0.0357 (4)
H220.7408310.3898790.7748030.043*
C230.8563 (2)0.1213 (5)0.85770 (13)0.0411 (5)
H230.9310250.0711580.8297630.049*
C240.8597 (2)0.0029 (5)0.93049 (12)0.0392 (5)
H240.9363550.1289950.9525430.047*
C250.7510 (2)0.0775 (4)0.97097 (11)0.0357 (4)
H250.7517210.0066041.0204290.043*
C260.6400 (2)0.2755 (4)0.93970 (10)0.0300 (4)
H260.5673700.3294800.9685320.036*
H7C0.599 (3)0.242 (7)0.5371 (11)0.063 (8)*
H7D0.527 (3)0.099 (4)0.5837 (15)0.049 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0261 (5)0.0249 (6)0.0194 (5)0.0041 (5)0.0033 (4)0.0010 (4)
O20.0268 (6)0.0252 (6)0.0228 (5)0.0056 (5)0.0032 (4)0.0036 (5)
O30.0303 (6)0.0431 (8)0.0214 (5)0.0104 (6)0.0075 (5)0.0041 (5)
O40.0324 (6)0.0276 (6)0.0260 (6)0.0030 (5)0.0134 (5)0.0026 (5)
O50.0455 (7)0.0300 (7)0.0183 (5)0.0057 (6)0.0001 (5)0.0007 (5)
O60.0252 (5)0.0319 (7)0.0309 (6)0.0053 (5)0.0050 (4)0.0046 (5)
O70.0444 (7)0.0294 (7)0.0362 (7)0.0025 (6)0.0207 (6)0.0032 (6)
C10.0241 (7)0.0283 (8)0.0195 (7)0.0012 (7)0.0030 (6)0.0016 (6)
C20.0228 (7)0.0189 (7)0.0196 (6)0.0001 (6)0.0039 (5)0.0010 (6)
C30.0248 (7)0.0172 (7)0.0207 (6)0.0014 (6)0.0070 (5)0.0008 (6)
C40.0304 (8)0.0176 (8)0.0204 (7)0.0005 (6)0.0033 (6)0.0006 (6)
C50.0258 (8)0.0226 (8)0.0229 (7)0.0023 (6)0.0019 (6)0.0015 (6)
C60.0235 (7)0.0245 (8)0.0216 (7)0.0021 (6)0.0047 (6)0.0005 (6)
C70.0301 (8)0.0410 (10)0.0224 (7)0.0110 (8)0.0064 (6)0.0006 (7)
C80.0343 (10)0.0628 (16)0.0679 (15)0.0120 (11)0.0235 (10)0.0125 (13)
C210.0246 (7)0.0265 (8)0.0242 (7)0.0005 (7)0.0008 (6)0.0034 (6)
C220.0310 (9)0.0427 (12)0.0342 (9)0.0064 (8)0.0096 (7)0.0068 (8)
C230.0303 (9)0.0487 (12)0.0438 (10)0.0108 (9)0.0080 (8)0.0016 (10)
C240.0350 (9)0.0380 (11)0.0372 (10)0.0098 (9)0.0060 (8)0.0039 (9)
C250.0442 (10)0.0344 (10)0.0227 (8)0.0058 (8)0.0034 (7)0.0005 (7)
C260.0322 (8)0.0331 (10)0.0219 (7)0.0037 (7)0.0011 (6)0.0023 (7)
Geometric parameters (Å, º) top
O1—C11.4250 (18)C4—C51.535 (2)
O1—C21.4305 (18)C4—H41.0000
O2—C51.4218 (19)C5—H51.0000
O2—C61.4280 (19)C6—C71.516 (2)
O3—C11.4141 (19)C6—H61.0000
O3—C71.436 (2)C7—H7A0.9900
O4—C31.4281 (17)C7—H7B0.9900
O4—H4A0.8400C8—H8A0.9800
O5—C41.4191 (19)C8—H8B0.9800
O5—H5A0.8400C8—H8C0.9800
O6—C51.404 (2)C21—C261.387 (2)
O6—C81.425 (2)C21—C221.392 (2)
O7—H7C0.841 (12)C22—C231.386 (3)
O7—H7D0.832 (13)C22—H220.9500
C1—C211.507 (2)C23—C241.383 (3)
C1—H11.0000C23—H230.9500
C2—C31.5140 (19)C24—C251.382 (3)
C2—C61.515 (2)C24—H240.9500
C2—H21.0000C25—C261.396 (3)
C3—C41.519 (2)C25—H250.9500
C3—H31.0000C26—H260.9500
C1—O1—C2109.23 (11)O2—C6—C2109.77 (12)
C5—O2—C6111.43 (12)O2—C6—C7109.48 (13)
C1—O3—C7111.18 (13)C2—C6—C7108.66 (12)
C3—O4—H4A109.5O2—C6—H6109.6
C4—O5—H5A109.5C2—C6—H6109.6
C5—O6—C8112.74 (16)C7—C6—H6109.6
H7C—O7—H7D107 (2)O3—C7—C6107.50 (14)
O3—C1—O1111.33 (12)O3—C7—H7A110.2
O3—C1—C21109.72 (13)C6—C7—H7A110.2
O1—C1—C21108.27 (13)O3—C7—H7B110.2
O3—C1—H1109.2C6—C7—H7B110.2
O1—C1—H1109.2H7A—C7—H7B108.5
C21—C1—H1109.2O6—C8—H8A109.5
O1—C2—C3109.66 (12)O6—C8—H8B109.5
O1—C2—C6108.61 (12)H8A—C8—H8B109.5
C3—C2—C6110.24 (12)O6—C8—H8C109.5
O1—C2—H2109.4H8A—C8—H8C109.5
C3—C2—H2109.4H8B—C8—H8C109.5
C6—C2—H2109.4C26—C21—C22119.16 (17)
O4—C3—C2111.45 (12)C26—C21—C1122.25 (15)
O4—C3—C4108.54 (12)C22—C21—C1118.55 (15)
C2—C3—C4108.92 (12)C23—C22—C21120.60 (18)
O4—C3—H3109.3C23—C22—H22119.7
C2—C3—H3109.3C21—C22—H22119.7
C4—C3—H3109.3C24—C23—C22120.16 (19)
O5—C4—C3108.23 (13)C24—C23—H23119.9
O5—C4—C5111.15 (13)C22—C23—H23119.9
C3—C4—C5111.52 (12)C25—C24—C23119.63 (18)
O5—C4—H4108.6C25—C24—H24120.2
C3—C4—H4108.6C23—C24—H24120.2
C5—C4—H4108.6C24—C25—C26120.48 (18)
O6—C5—O2111.81 (13)C24—C25—H25119.8
O6—C5—C4106.76 (13)C26—C25—H25119.8
O2—C5—C4111.56 (13)C21—C26—C25119.94 (17)
O6—C5—H5108.9C21—C26—H26120.0
O2—C5—H5108.9C25—C26—H26120.0
C4—C5—H5108.9
C7—O3—C1—O162.57 (18)C5—O2—C6—C263.05 (16)
C7—O3—C1—C21177.59 (14)C5—O2—C6—C7177.76 (14)
C2—O1—C1—O362.49 (17)O1—C2—C6—O2178.67 (12)
C2—O1—C1—C21176.82 (13)C3—C2—C6—O261.17 (16)
C1—O1—C2—C3179.03 (12)O1—C2—C6—C758.97 (17)
C1—O1—C2—C660.45 (15)C3—C2—C6—C7179.13 (14)
O1—C2—C3—O465.88 (16)C1—O3—C7—C659.08 (18)
C6—C2—C3—O4174.60 (13)O2—C6—C7—O3177.12 (13)
O1—C2—C3—C4174.40 (12)C2—C6—C7—O357.25 (18)
C6—C2—C3—C454.88 (16)O3—C1—C21—C2616.3 (2)
O4—C3—C4—O565.17 (16)O1—C1—C21—C26138.00 (16)
C2—C3—C4—O5173.32 (13)O3—C1—C21—C22165.85 (16)
O4—C3—C4—C5172.26 (12)O1—C1—C21—C2244.2 (2)
C2—C3—C4—C550.76 (16)C26—C21—C22—C231.2 (3)
C8—O6—C5—O263.6 (2)C1—C21—C22—C23176.72 (19)
C8—O6—C5—C4174.09 (16)C21—C22—C23—C241.6 (3)
C6—O2—C5—O660.50 (16)C22—C23—C24—C250.3 (3)
C6—O2—C5—C458.97 (17)C23—C24—C25—C261.4 (3)
O5—C4—C5—O651.55 (16)C22—C21—C26—C250.4 (3)
C3—C4—C5—O669.32 (16)C1—C21—C26—C25178.28 (17)
O5—C4—C5—O2173.98 (13)C24—C25—C26—C211.7 (3)
C3—C4—C5—O253.10 (17)
Hydrogen-bond geometry (Å, º) top
Cg(1) is the centroid of carbon atoms C21–C26.
D—H···AD—HH···AD···AD—H···A
O4—H4A···O70.841.862.6925 (19)172
O5—H5A···O5i0.842.483.1906 (18)143
O5—H5A···O6i0.842.122.8486 (18)145
O7—H7C···O4ii0.84 (1)2.08 (2)2.8758 (17)159 (3)
O7—H7D···O4iii0.83 (1)2.02 (1)2.8444 (19)175 (3)
C5—H5···O5i1.002.463.299 (2)141
C8—H8C···O7iv0.982.433.380 (3)163
C1—H1···Cg(1)v1.002.563.516 (2)161
Symmetry codes: (i) x, y+1/2, z+1; (ii) x+1, y1/2, z+1; (iii) x, y1, z; (iv) x1, y, z; (v) x, y+1, z.
 

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