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The title compound, C21H28O8, crystallizes with two independent mol­ecules, each with a crystallographic twofold axis passing through the central CH2 group. The two mol­ecules have different orientations of the terminal benzyl groups. The average C—O bond length in the polyoxymethyl­ene helix, corrected for librational motion, is 1.419 Å. The mol­ecules are connected into layers by inter­molecular C—H...O and C—H...π(phenyl) inter­actions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107004830/jz3053sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107004830/jz3053Isup2.hkl
Contains datablock I

CCDC reference: 641815

Comment top

The synthesis of polyoxymethylene helices that are terminated at both ends by phenyl groups has been reported by Noe et al. (1994). We have previously reported the crystal structure of 1,13-diphenyl-2,4,6,8,10,12-hexaoxatridecane (Noe et al., 1994). Here, we report the structure of the related title compound, (I).

Crystals of (I) undergo a reversible phase transition at approximately 155 K, accompanied by a splitting of the reflection profiles in the low-temperature phase. The structure determination of (I) was performed at 178 K, which is well above the phase-transition temperature. The crystal structure of (I) is isomorphous with that of 1,13-diphenyl-2,4,6,8,10,12-hexaoxatridecane (Noe et al., 1994).

The molecular structure of compound (I) is shown in Fig. 1. The compound crystallizes with two independent molecules (A and B), each displaying crystallographic twofold symmetry, with the axis passing through the central CH2 group. The helical molecule has a chiral axis and both independent molecules have the same chirality. There should be no preference for the molecules to adopt left- or right-handed helices, and thus the bulk material is expected to be a racemate that crystallizes into equal amounts of enantiomorphous crystals.

The two independent molecules in (I) have different orientations of the terminal benzyl groups. The phenyl group of molecule A is synperiplanar with the C7—O1 bond [torsion angle C2—C1—C7—O1 = -29.47 (18)°], while the phenyl group of molecule B is almost perpendicular to the C18—O5 bond [torsion angle C17—C12—C18—O5 = -78.76 (18)°]. An almost constant C—O bond length, varying between 1.4067 (17) and 1.4192 (16) Å with an average of 1.413 Å, is observed in the regions C8–C8(1 - x, y, -z) and C19—C19(1 - x, y, 1 - z). The polyoxymethylene helices (without the benzyl groups) behave as rigid bodies with rather large librational motion along the helix axis [51 (2)°2 for molecule A and 45 (2)°2 for molecule B] but with almost no librational motion about axes perpendicular to the molecular axis. The average C—O bond length, corrected for librational motion, is 1.419 Å. A value of 1.420 Å was observed in the structure of the related compound 1,15-diphenylheptaoxapentadecane (Bats et al., 2001). These values are in good agreement with the C—O bond lengths of 1.423 and 1.417 Å obtained from ab initio calculations of dimethoxymethane (Jeffrey et al., 1978) and 1,3-dimethoxydimethyl ether (Sawanobori et al., 2001). A major factor stabilizing the helix structure is the stereoelectronic effect (Kirby, 1983; Deslongchamps, 1984), which results in a preference of gauche conformations (all-g+ or all-g-) over trans conformations for the conjugated C—O bonds. The helix is also stabilized by intramolecular 14 C—H···O interactions. The helix of molecule A shows 14 such interactions with H···O distances between 2.54 and 2.57 Å, while the helix of molecule B shows 12 interactions with H···O distances between 2.50 and 2.61 Å.

No stereoelectronic effects are expected for the terminal O—Cbenzyl bonds. Those bond lengths are 1.4276 (19) and 1.4360 (16) Å, respectively, and thus are significantly longer than the remaining C—O bonds. The O1—C8 and O5—C19 bonds in (I) are surprisingly short, at 1.3985 (16) and 1.3981 (16) Å, respectively. This bond shortening at the ends of the helices is significant, but its origin is not clearly understood. However, this bond-length variation is reproduced in the ab initio calculation of 1,3-dimethoxydimethyl ether (Sawanobori et al., 2001).

The C—O—C bond angles in (I) range between 113.47 (10) and 114.40 (9)° and are almost constant, with an average value of 114.20°. The O—C—O angles range between 112.17 (17) and 113.18 (12)° and these values are also almost constant, with an average value of 112.62°. The C—O—C—O torsion angles vary between -61.37 (14) and -68.85 (13)°, with an average value of -65.50°. Almost constant torsion angles, corresponding to an undisturbed helix, are found in molecule A. The helix of molecule B is slightly bent, resulting in deviations of the C—O—C—O torsion angles by up to 4° from their average value.

The crystal packing in (I), shown in Fig. 2, is stabilized by a number of intermolecular C—H···O and C—H···π(phenyl) interactions. Each molecule A is connected to four symmetry-related molecules B, and each molecule B is connected to four symmetry-related molecules A. There are no contacts between molecules A or between molecules B. The molecules are arranged by these intermolecular interactions to form layers parallel to (100). The C—H···O contacts with H···O distances of less than 2.61 Å are reported in Table 1. This cut-off value was chosen arbitrarily and there are several additional contacts with still longer distances. The molecules in the layers are also connected by weak intermolecular C(phenyl)—H···π(phenyl) interactions, which have been included in Table 1 (Cg1 and Cg2 represent the centroids of the phenyl rings of molecules A and B). The C—H donor groups do not point to the midpoint of the acceptor phenyl groups but instead are closer to individual C atoms of the acceptor rings. The shortest H···C distances for the four contacts are 2.92, 2.84, 2.94 and 2.86 Å. There are no short intermolecular contacts between the layers along the a direction.

Related literature top

For related literature, see: Bats et al. (2001); Deslongchamps (1984); Farrugia (1999); Jeffrey et al. (1978); Kirby (1983); Noe et al. (1994); Sawanobori et al. (2001).

Experimental top

Compound (I) was prepared as described by Noe et al. (1994). Thin plates were obtained by crystallization from chloroform–hexane (Ratio?) at low temperature.

Refinement top

H atoms were located in a difference Fourier map and refined as riding, with C(sp2)—H = 0.95 Å and Csecondary—H = 0.99 Å, with Uiso(H) = 1.2Ueq(C). Friedel opposites were not merged. The absolute structure was determined from the anomalous scattering contribution of the O atoms, using 1511 Friedel pairs. The thermal motion analysis was performed using the WinGX program package (Farrugia, 1999).

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1996); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The structures of the two independent molecules of (I), with the atom-numbering schemes. Displacement ellipsoids are drawn at the 50% probability level. Molecule A is at the top and molecule B at the bottom. Unlabelled atoms are related to labelled atoms by the symmetry operator (1 - x, y, -z) in molecule A and by (1 - x, y, 1 - z) in molecule B. [Please check added text]
[Figure 2] Fig. 2. The crystal packing of (I), viewed down the b axis. Intermolecular C—H···O contacts with H···O distances shorter than 2.60 Å are shown as broken lines. The positions of molecules A and B are marked by symbols A and B. The molecules are connected into layers parallel to (100) by additional intermolecular interactions along b (not shown). [Symmetry codes: (i) x, y, z - 1; (ii) x, y, z + 1.]
1,17-Diphenyl-2,4,6,8,10,12,14,16-octaoxaheptadecane top
Crystal data top
C21H28O8F(000) = 872
Mr = 408.43Dx = 1.299 Mg m3
Monoclinic, C2Cu Kα radiation, λ = 1.54180 Å
Hall symbol: C 2yCell parameters from 25 reflections
a = 47.506 (8) Åθ = 36–50°
b = 5.392 (2) ŵ = 0.83 mm1
c = 8.288 (2) ÅT = 178 K
β = 100.38 (2)°Thin plate, colourless
V = 2088.3 (10) Å30.55 × 0.55 × 0.04 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer
3591 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.043
Graphite monochromatorθmax = 70.0°, θmin = 1.9°
ω scansh = 5757
Absorption correction: numerical
(SHELXTL; Sheldrick, 1996)
k = 65
Tmin = 0.601, Tmax = 0.969l = 109
8436 measured reflections3 standard reflections every 92 min
3716 independent reflections intensity decay: 0.0%
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.036 w = 1/[σ2(Fo2) + (0.07P)2 + 0.26P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.100(Δ/σ)max = 0.004
S = 1.08Δρmax = 0.20 e Å3
3716 reflectionsΔρmin = 0.15 e Å3
264 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.00080 (13)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), with 1511 Friedel pairs
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.12 (15)
Crystal data top
C21H28O8V = 2088.3 (10) Å3
Mr = 408.43Z = 4
Monoclinic, C2Cu Kα radiation
a = 47.506 (8) ŵ = 0.83 mm1
b = 5.392 (2) ÅT = 178 K
c = 8.288 (2) Å0.55 × 0.55 × 0.04 mm
β = 100.38 (2)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
3591 reflections with I > 2σ(I)
Absorption correction: numerical
(SHELXTL; Sheldrick, 1996)
Rint = 0.043
Tmin = 0.601, Tmax = 0.9693 standard reflections every 92 min
8436 measured reflections intensity decay: 0.0%
3716 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.036H-atom parameters constrained
wR(F2) = 0.100Δρmax = 0.20 e Å3
S = 1.08Δρmin = 0.15 e Å3
3716 reflectionsAbsolute structure: Flack (1983), with 1511 Friedel pairs
264 parametersAbsolute structure parameter: 0.12 (15)
1 restraint
Special details top

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
O10.38902 (2)0.1043 (2)0.32502 (11)0.0415 (3)
O20.407524 (18)0.1299 (2)0.08172 (10)0.0362 (2)
O30.456702 (18)0.1167 (2)0.18980 (10)0.0356 (2)
O40.475385 (17)0.1237 (2)0.05420 (9)0.0350 (2)
O50.375388 (19)0.5635 (2)0.65927 (10)0.0376 (3)
O60.424644 (18)0.60453 (19)0.75902 (10)0.0360 (2)
O70.441967 (18)0.6226 (2)0.51124 (10)0.0362 (2)
O80.490993 (18)0.6335 (2)0.62303 (10)0.0351 (2)
C10.33698 (3)0.1333 (3)0.22644 (15)0.0370 (3)
C20.33454 (3)0.3462 (3)0.31737 (16)0.0357 (3)
H20.35020.39720.39830.043*
C30.30968 (3)0.4854 (4)0.29227 (19)0.0482 (4)
H30.30850.63060.35560.058*
C40.28690 (3)0.4148 (5)0.1770 (2)0.0649 (6)
H40.26980.50960.16040.078*
C50.28886 (4)0.2051 (5)0.0845 (2)0.0736 (7)
H50.27300.15610.00380.088*
C60.31382 (4)0.0645 (4)0.10822 (17)0.0577 (5)
H60.31500.07900.04320.069*
C70.36332 (3)0.0264 (3)0.2605 (2)0.0487 (4)
H7A0.36030.15750.33930.058*
H7B0.36580.10900.15720.058*
C80.39871 (3)0.2614 (3)0.21240 (15)0.0348 (3)
H8A0.41500.36050.27020.042*
H8B0.38320.37770.16680.042*
C90.43180 (3)0.0219 (3)0.13034 (15)0.0375 (3)
H9A0.42810.13710.21710.045*
H9B0.43500.12260.03550.045*
C100.46634 (2)0.2659 (3)0.07022 (14)0.0345 (3)
H10A0.45070.37760.01990.041*
H10B0.48240.37030.12430.041*
C110.50000.0218 (4)0.00000.0365 (4)
H11A0.49650.12990.09090.044*
C120.33434 (3)0.7404 (3)0.74043 (15)0.0388 (3)
C130.31284 (3)0.5872 (3)0.77704 (18)0.0452 (4)
H130.31770.44060.83950.054*
C140.28439 (3)0.6473 (4)0.72284 (19)0.0506 (4)
H140.26980.54390.75070.061*
C150.27713 (3)0.8547 (3)0.6294 (2)0.0485 (4)
H150.25760.89290.59040.058*
C160.29827 (3)1.0079 (4)0.59181 (19)0.0492 (4)
H160.29331.15200.52710.059*
C170.32667 (3)0.9521 (3)0.64808 (17)0.0458 (4)
H170.34111.05980.62330.055*
C180.36524 (3)0.6737 (4)0.79578 (16)0.0486 (4)
H18A0.37650.82400.83300.058*
H18B0.36730.55510.88830.058*
C190.40162 (3)0.4415 (3)0.70341 (15)0.0367 (3)
H19A0.40570.34820.60740.044*
H19B0.40010.32020.79120.044*
C200.43197 (3)0.7586 (3)0.63567 (15)0.0364 (3)
H20A0.44700.87650.68590.044*
H20B0.41500.85640.58580.044*
C210.46692 (3)0.4839 (3)0.56643 (15)0.0363 (3)
H21A0.47100.37840.47550.044*
H21B0.46360.37310.65630.044*
C220.50000.7800 (4)0.50000.0358 (4)
H22A0.48400.88810.44890.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0431 (5)0.0518 (7)0.0334 (4)0.0098 (5)0.0165 (4)0.0096 (5)
O20.0347 (4)0.0502 (6)0.0248 (4)0.0032 (5)0.0083 (3)0.0010 (4)
O30.0349 (4)0.0494 (6)0.0234 (4)0.0041 (4)0.0079 (3)0.0006 (4)
O40.0343 (5)0.0490 (6)0.0226 (4)0.0050 (4)0.0075 (3)0.0000 (4)
O50.0346 (5)0.0546 (7)0.0247 (4)0.0001 (4)0.0085 (3)0.0048 (4)
O60.0344 (4)0.0484 (6)0.0250 (4)0.0046 (4)0.0048 (3)0.0012 (4)
O70.0364 (5)0.0479 (6)0.0246 (4)0.0024 (4)0.0063 (3)0.0004 (4)
O80.0368 (4)0.0453 (6)0.0238 (4)0.0043 (4)0.0067 (3)0.0003 (4)
C10.0432 (7)0.0420 (8)0.0299 (6)0.0106 (6)0.0174 (5)0.0007 (6)
C20.0354 (6)0.0408 (8)0.0321 (6)0.0034 (6)0.0090 (5)0.0001 (5)
C30.0455 (8)0.0540 (10)0.0504 (8)0.0069 (7)0.0226 (6)0.0147 (7)
C40.0368 (8)0.0941 (17)0.0640 (11)0.0003 (9)0.0097 (7)0.0371 (12)
C50.0492 (9)0.1164 (19)0.0475 (9)0.0357 (11)0.0118 (7)0.0258 (11)
C60.0724 (11)0.0698 (12)0.0321 (7)0.0338 (9)0.0127 (7)0.0047 (7)
C70.0565 (9)0.0378 (9)0.0601 (9)0.0018 (7)0.0331 (7)0.0000 (7)
C80.0338 (6)0.0398 (8)0.0323 (7)0.0003 (6)0.0099 (5)0.0016 (6)
C90.0425 (7)0.0407 (8)0.0325 (7)0.0001 (6)0.0152 (5)0.0008 (6)
C100.0317 (6)0.0400 (8)0.0321 (7)0.0003 (5)0.0068 (5)0.0006 (5)
C110.0415 (10)0.0405 (11)0.0303 (9)0.0000.0140 (7)0.000
C120.0431 (7)0.0475 (8)0.0289 (6)0.0010 (6)0.0148 (5)0.0062 (6)
C130.0549 (8)0.0396 (9)0.0442 (7)0.0013 (7)0.0175 (6)0.0023 (7)
C140.0474 (8)0.0524 (10)0.0570 (9)0.0098 (7)0.0230 (6)0.0022 (8)
C150.0409 (7)0.0536 (10)0.0544 (9)0.0055 (7)0.0180 (6)0.0032 (7)
C160.0548 (8)0.0449 (9)0.0509 (8)0.0072 (7)0.0178 (6)0.0066 (7)
C170.0474 (8)0.0491 (9)0.0451 (8)0.0058 (7)0.0201 (6)0.0016 (7)
C180.0456 (7)0.0738 (12)0.0278 (6)0.0068 (8)0.0103 (5)0.0100 (7)
C190.0400 (7)0.0410 (9)0.0310 (6)0.0006 (6)0.0115 (5)0.0002 (6)
C200.0354 (7)0.0391 (8)0.0351 (7)0.0032 (6)0.0077 (5)0.0008 (6)
C210.0414 (7)0.0374 (8)0.0323 (7)0.0002 (6)0.0125 (6)0.0006 (5)
C220.0359 (9)0.0377 (11)0.0332 (9)0.0000.0049 (7)0.000
Geometric parameters (Å, º) top
O1—C81.3985 (16)C8—H8B0.9900
O1—C71.4276 (19)C9—H9A0.9900
O2—C91.4125 (18)C9—H9B0.9900
O2—C81.4192 (16)C10—H10A0.9900
O3—C91.4109 (18)C10—H10B0.9900
O3—C101.4150 (16)C11—O4i1.4125 (16)
O4—C101.4124 (16)C11—H11A0.9900
O4—C111.4127 (16)C11—H11Ai0.9900
O5—C191.3981 (16)C12—C171.386 (2)
O5—C181.4360 (16)C12—C131.389 (2)
O6—C201.4088 (17)C12—C181.5008 (19)
O6—C191.4141 (17)C13—C141.384 (2)
O7—C211.4067 (17)C13—H130.9500
O7—C201.4156 (16)C14—C151.369 (2)
O8—C211.4091 (17)C14—H140.9500
O8—C221.4156 (15)C15—C161.379 (2)
C1—C61.386 (2)C15—H150.9500
C1—C21.390 (2)C16—C171.379 (2)
C1—C71.503 (2)C16—H160.9500
C2—C31.383 (2)C17—H170.9500
C2—H20.9500C18—H18A0.9900
C3—C41.363 (3)C18—H18B0.9900
C3—H30.9500C19—H19A0.9900
C4—C51.379 (3)C19—H19B0.9900
C4—H40.9500C20—H20A0.9900
C5—C61.391 (3)C20—H20B0.9900
C5—H50.9500C21—H21A0.9900
C6—H60.9500C21—H21B0.9900
C7—H7A0.9900C22—O8ii1.4156 (15)
C7—H7B0.9900C22—H22A0.9900
C8—H8A0.9900C22—H22Aii0.9900
C8—O1—C7114.26 (10)O4—C11—H11A109.1
C9—O2—C8114.19 (9)O4i—C11—H11Ai109.1
C9—O3—C10114.40 (9)O4—C11—H11Ai109.1
C10—O4—C11114.37 (8)H11A—C11—H11Ai107.8
C19—O5—C18113.47 (10)C17—C12—C13118.68 (13)
C20—O6—C19114.06 (9)C17—C12—C18120.79 (14)
C21—O7—C20114.36 (9)C13—C12—C18120.51 (15)
C21—O8—C22114.34 (8)C14—C13—C12120.21 (15)
C6—C1—C2118.11 (15)C14—C13—H13119.9
C6—C1—C7120.50 (15)C12—C13—H13119.9
C2—C1—C7121.31 (12)C15—C14—C13120.46 (14)
C3—C2—C1121.28 (14)C15—C14—H14119.8
C3—C2—H2119.4C13—C14—H14119.8
C1—C2—H2119.4C14—C15—C16119.86 (15)
C4—C3—C2120.21 (18)C14—C15—H15120.1
C4—C3—H3119.9C16—C15—H15120.1
C2—C3—H3119.9C15—C16—C17120.07 (15)
C3—C4—C5119.59 (18)C15—C16—H16120.0
C3—C4—H4120.2C17—C16—H16120.0
C5—C4—H4120.2C16—C17—C12120.70 (14)
C4—C5—C6120.67 (15)C16—C17—H17119.7
C4—C5—H5119.7C12—C17—H17119.7
C6—C5—H5119.7O5—C18—C12107.88 (10)
C1—C6—C5120.14 (18)O5—C18—H18A110.1
C1—C6—H6119.9C12—C18—H18A110.1
C5—C6—H6119.9O5—C18—H18B110.1
O1—C7—C1114.49 (13)C12—C18—H18B110.1
O1—C7—H7A108.6H18A—C18—H18B108.4
C1—C7—H7A108.6O5—C19—O6113.18 (12)
O1—C7—H7B108.6O5—C19—H19A108.9
C1—C7—H7B108.6O6—C19—H19A108.9
H7A—C7—H7B107.6O5—C19—H19B108.9
O1—C8—O2112.61 (12)O6—C19—H19B108.9
O1—C8—H8A109.1H19A—C19—H19B107.8
O2—C8—H8A109.1O6—C20—O7112.47 (13)
O1—C8—H8B109.1O6—C20—H20A109.1
O2—C8—H8B109.1O7—C20—H20A109.1
H8A—C8—H8B107.8O6—C20—H20B109.1
O3—C9—O2112.51 (14)O7—C20—H20B109.1
O3—C9—H9A109.1H20A—C20—H20B107.8
O2—C9—H9A109.1O7—C21—O8112.93 (14)
O3—C9—H9B109.1O7—C21—H21A109.0
O2—C9—H9B109.1O8—C21—H21A109.0
H9A—C9—H9B107.8O7—C21—H21B109.0
O4—C10—O3112.48 (13)O8—C21—H21B109.0
O4—C10—H10A109.1H21A—C21—H21B107.8
O3—C10—H10A109.1O8ii—C22—O8112.17 (17)
O4—C10—H10B109.1O8ii—C22—H22A109.2
O3—C10—H10B109.1O8—C22—H22A109.2
H10A—C10—H10B107.8O8ii—C22—H22Aii109.2
O4i—C11—O4112.51 (18)O8—C22—H22Aii109.2
O4i—C11—H11A109.1H22A—C22—H22Aii107.9
C6—C1—C2—C30.53 (19)C17—C12—C13—C140.5 (2)
C7—C1—C2—C3176.29 (13)C18—C12—C13—C14178.72 (14)
C1—C2—C3—C40.2 (2)C12—C13—C14—C151.6 (2)
C2—C3—C4—C50.6 (2)C13—C14—C15—C161.4 (2)
C3—C4—C5—C60.2 (3)C14—C15—C16—C170.1 (2)
C2—C1—C6—C50.8 (2)C15—C16—C17—C121.0 (2)
C7—C1—C6—C5176.02 (14)C13—C12—C17—C160.8 (2)
C4—C5—C6—C10.5 (2)C18—C12—C17—C16177.40 (14)
C8—O1—C7—C170.30 (15)C19—O5—C18—C12166.02 (13)
C6—C1—C7—O1153.78 (13)C17—C12—C18—O578.76 (18)
C2—C1—C7—O129.47 (18)C13—C12—C18—O599.43 (15)
C7—O1—C8—O266.13 (14)C18—O5—C19—O667.62 (14)
C9—O2—C8—O165.52 (14)C20—O6—C19—O568.85 (13)
C10—O3—C9—O266.41 (13)C19—O6—C20—O763.70 (13)
C8—O2—C9—O365.90 (13)C21—O7—C20—O661.37 (14)
C11—O4—C10—O365.99 (13)C20—O7—C21—O866.00 (14)
C9—O3—C10—O465.11 (13)C22—O8—C21—O765.72 (13)
C10—O4—C11—O4i65.55 (9)C21—O8—C22—O8ii63.05 (9)
Symmetry codes: (i) x+1, y, z; (ii) x+1, y, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O50.952.453.345 (2)158
C8—H8A···O70.992.593.510 (2)155
C10—H10A···O6iii0.992.603.474 (2)148
C19—H19B···O2iv0.992.583.524 (2)159
C22—H22A···O3v0.992.613.497 (2)149
C3—H3···Cg20.952.903.702143
C6—H6···Cg2vi0.953.003.745137
C13—H13···Cg1iv0.953.193.905134
C16—H16···Cg1v0.953.063.705126
Symmetry codes: (iii) x, y, z1; (iv) x, y, z+1; (v) x, y+1, z; (vi) x, y1, z1.

Experimental details

Crystal data
Chemical formulaC21H28O8
Mr408.43
Crystal system, space groupMonoclinic, C2
Temperature (K)178
a, b, c (Å)47.506 (8), 5.392 (2), 8.288 (2)
β (°) 100.38 (2)
V3)2088.3 (10)
Z4
Radiation typeCu Kα
µ (mm1)0.83
Crystal size (mm)0.55 × 0.55 × 0.04
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correctionNumerical
(SHELXTL; Sheldrick, 1996)
Tmin, Tmax0.601, 0.969
No. of measured, independent and
observed [I > 2σ(I)] reflections
8436, 3716, 3591
Rint0.043
(sin θ/λ)max1)0.609
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.100, 1.08
No. of reflections3716
No. of parameters264
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.20, 0.15
Absolute structureFlack (1983), with 1511 Friedel pairs
Absolute structure parameter0.12 (15)

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CAD-4, MolEN (Fair, 1990), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1996), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O50.952.453.345 (2)158
C8—H8A···O70.992.593.510 (2)155
C10—H10A···O6i0.992.603.474 (2)148
C19—H19B···O2ii0.992.583.524 (2)159
C22—H22A···O3iii0.992.613.497 (2)149
C3—H3···Cg20.952.903.702143
C6—H6···Cg2iv0.953.003.745137
C13—H13···Cg1ii0.953.193.905134
C16—H16···Cg1iii0.953.063.705126
Symmetry codes: (i) x, y, z1; (ii) x, y, z+1; (iii) x, y+1, z; (iv) x, y1, z1.
 

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