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The title compound, C20H22O6, has crystallographic twofold symmetry. The central six-C-atom chain has an extended conformation similar to that of D-mannitol, with two independent C-C-C-C torsion angles of 165.69 (14) and 177.60 (12)°. The 1,3-dioxane ring has a chair conformation. All chiral centers have the R configuration.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100001591/da1113sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100001591/da1113Isup2.hkl
Contains datablock I

CCDC reference: 145542

Comment top

The use of carbohydrates as inexpensive starting materials and building blocks is of great interest (Bols, 1996). For example, D-mannitol, which has C2 symmetry, offers unique synthetic approaches to chiral auxiliaries (Defoin et al., 1991; Masaki et al., 1992) and chiral drugs (Poitout et al., 1994). Benzylidene acetal is a commonly used temporary protective group for D-mannitol because of its stability to most reaction conditions and high-yielding deprotection step (Greene & Wuts, 1991). The title compound, (I), is a benzylidene-protected mannitol. The elucidation of its structure was carried out to study the effect of the two six-membered 1,3-dioxane rings on the conformation of the central six-C-atom mannitol core. \scheme

Fig. 1 shows the atomic numbering scheme and conformationof (I). The molecule lies on a crystallographic twofold axis. The chiral centers C2, C3 and C7 all have the R configuration. The six-membered benzylidene acetal 1,3-dioxane ring adopts a chair conformation, with endocyclic torsion angles in the range 44.54 (14)–68.55 (13)°. All substituents are in equatorial positions. The torsion angles formed by the six central C atoms of (I) are comparable with those in DL-mannitol (Kanters et al., 1977), D-mannitol (Berman et al., 1968; Kim et al., 1968) and hexaacetal-D-mannitol (Stein et al., 1992), despite the presence of the 1,3-dioxane ring. While in all these cases the conformation is anti-anti-anti, deviations from 180° vary by up to about 20°. In (I), there are only two such independent torsion angles, as a result of the molecular symmetry. These are C1—C2—C3—C3i [165.69 (14)°; symmetry code: (i) 1 - x, y, -z] and C2—C3—C3i—C2i [177.60 (12)°]. None of the other mannitols retain their C2 symmetry in the crystal, and thus have three independent torsion angles. In DL-mannitol (Kanters et al., 1977) they are -175.9 (4), -176.5 (4) and 174.8 (4)°, in β-D-mannitol (Berman et al., 1968) they are -175.3 (6), 175.8 (6) and -179.8 (6)°, in K—D-mannitol (Kim et al., 1968) they are -174.8 (3), 175.8 (3) and -176.5 (3)°, and in hexaacetal-D-mannitol (Stein et al., 1992) they are -175.3 (5), 159.8 (5) and -173.2 (5)°. The main difference in conformation between (I) and the cited acyclic mannitols is the torsion angle involving vicinal O atoms, O1—C1—C2—O2 [-169.52 (11)°]. Cyclization forces the O atoms to be antiperiplanar, while they are gauche [torsion angle magnitudes 58.0 (3)–65.6 (7)°] in the acyclic mannitols.

The phenyl ring in (I) is planar, with a maximum deviation of 0.006 (2) Å for C11. Molecules form weakly hydrogen-bonded chains in the symmetry direction, via pairs of O2—H···O1ii interactions [symmetry code: (ii) x, y - 1, z]. Both OH groups of each molecule donate to 1,3-dioxane O atoms of the same translation-related adjacent molecule. The O···O distance in this interaction is 3.183 (2) Å and the angle about the H atom is 158 (3)°.

Experimental top

Compound (I) was prepared by acetalization of D-mannitol with benzaldehyde (Baggett & Stribblehill, 1977). A suitable crystal used for data collection was obtained by slow evaporation of an ethanol solution at room temperature.

Refinement top

The absolute structure of (I) was determined by refinement of the Flack (1983) parameter, based on 713 Friedel pairs. The hydroxyl-H atom was refined isotropically. Other H atoms were placed in calculated positions with C—H bond distances 0.93 (phenyl) and 0.97 Å (sp3) and Uiso = 1.2Ueq of the attached C atom, and thereafter treated as riding.

Computing details top

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. Numbering scheme and ellipsoids at the 50% level. H atoms are shown as spheres of arbitrary radii.
1,3(R):4,6(R)-di-O-benzylidene-D-mannitol top
Crystal data top
C20H22O6F(000) = 380
Mr = 358.4Dx = 1.391 Mg m3
Monoclinic, C2Cu Kα radiation, λ = 1.54184 Å
a = 17.472 (4) ÅCell parameters from 25 reflections
b = 4.9237 (10) Åθ = 11.4–44.7°
c = 9.956 (2) ŵ = 0.85 mm1
β = 94.08 (3)°T = 293 K
V = 854.4 (3) Å3Lath, colorless
Z = 20.53 × 0.20 × 0.08 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1669 reflections with I > 2σ (I)
Radiation source: fine-focus sealed tubeRint = 0.027
Graphite monochromatorθmax = 75.0°, θmin = 4.5°
ω/2θ scansh = 2121
Absorption correction: ψ-scan
(North et al., 1968)
k = 65
Tmin = 0.668, Tmax = 0.934l = 1212
4158 measured reflections3 standard reflections every 60 min
1703 independent reflections intensity decay: 2.1%
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.033 w = 1/[σ2(Fo2) + (0.0677P)2 + 0.1745P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.093(Δ/σ)max = 0.002
S = 0.93Δρmax = 0.24 e Å3
1703 reflectionsΔρmin = 0.17 e Å3
123 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.0112 (14)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983)
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.10 (17)
Crystal data top
C20H22O6V = 854.4 (3) Å3
Mr = 358.4Z = 2
Monoclinic, C2Cu Kα radiation
a = 17.472 (4) ŵ = 0.85 mm1
b = 4.9237 (10) ÅT = 293 K
c = 9.956 (2) Å0.53 × 0.20 × 0.08 mm
β = 94.08 (3)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1669 reflections with I > 2σ (I)
Absorption correction: ψ-scan
(North et al., 1968)
Rint = 0.027
Tmin = 0.668, Tmax = 0.9343 standard reflections every 60 min
4158 measured reflections intensity decay: 2.1%
1703 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.033H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.093Δρmax = 0.24 e Å3
S = 0.93Δρmin = 0.17 e Å3
1703 reflectionsAbsolute structure: Flack (1983)
123 parametersAbsolute structure parameter: 0.10 (17)
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
O10.50423 (6)0.5698 (2)0.31592 (10)0.0511 (3)
O20.60265 (7)0.0003 (2)0.16337 (12)0.0591 (3)
O30.44908 (5)0.50526 (18)0.10141 (8)0.0418 (2)
C10.55167 (9)0.3333 (4)0.31024 (15)0.0538 (4)
H1A0.52650.18130.35060.065*
H1B0.59990.36540.36210.065*
C20.56748 (8)0.2617 (3)0.16613 (14)0.0456 (3)
H20.60310.39620.13340.055*
C30.49318 (7)0.2677 (3)0.07414 (12)0.0404 (3)
H30.46280.10690.09330.048*
C70.43442 (7)0.5197 (3)0.23842 (12)0.0407 (3)
H70.41310.34600.26610.049*
C80.37759 (7)0.7419 (3)0.25995 (12)0.0406 (3)
C90.33215 (8)0.8487 (4)0.15345 (14)0.0499 (3)
H90.33890.79090.06610.060*
C100.27670 (8)1.0408 (4)0.17589 (17)0.0605 (4)
H100.24671.11240.10340.073*
C110.26558 (8)1.1266 (4)0.30397 (17)0.0575 (4)
H110.22761.25350.31850.069*
C120.31099 (9)1.0238 (3)0.41129 (14)0.0539 (4)
H120.30401.08350.49820.065*
C130.36706 (8)0.8316 (3)0.39009 (13)0.0482 (3)
H130.39750.76280.46260.058*
H1O20.5664 (18)0.080 (8)0.203 (3)0.133 (12)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0536 (5)0.0418 (6)0.0560 (5)0.0044 (4)0.0084 (4)0.0081 (4)
O20.0600 (6)0.0429 (6)0.0740 (7)0.0154 (5)0.0018 (5)0.0029 (5)
O30.0475 (5)0.0358 (5)0.0426 (4)0.0052 (4)0.0062 (3)0.0010 (4)
C10.0577 (8)0.0462 (8)0.0555 (7)0.0093 (7)0.0097 (6)0.0011 (6)
C20.0452 (6)0.0329 (7)0.0585 (7)0.0030 (5)0.0016 (5)0.0040 (6)
C30.0426 (6)0.0294 (6)0.0496 (7)0.0007 (4)0.0055 (5)0.0020 (5)
C70.0464 (6)0.0336 (6)0.0423 (6)0.0044 (6)0.0035 (4)0.0011 (5)
C80.0426 (6)0.0345 (7)0.0452 (6)0.0061 (5)0.0065 (5)0.0003 (5)
C90.0453 (6)0.0557 (9)0.0482 (7)0.0015 (7)0.0011 (5)0.0081 (6)
C100.0469 (7)0.0696 (12)0.0635 (8)0.0089 (7)0.0066 (6)0.0018 (8)
C110.0456 (7)0.0511 (9)0.0768 (9)0.0044 (7)0.0113 (6)0.0090 (8)
C120.0624 (8)0.0478 (8)0.0536 (7)0.0052 (7)0.0187 (6)0.0058 (6)
C130.0594 (7)0.0429 (8)0.0431 (6)0.0029 (6)0.0087 (5)0.0043 (6)
Geometric parameters (Å, º) top
O1—C71.4179 (15)C3—C3i1.512 (2)
O1—C11.4328 (18)C7—C81.5032 (18)
O2—C21.4273 (17)C8—C91.382 (2)
O2—H1O20.83 (3)C8—C131.3934 (17)
O3—C71.4076 (14)C9—C101.384 (2)
O3—C31.4370 (15)C10—C111.370 (2)
C1—C21.522 (2)C11—C121.381 (2)
C2—C31.5349 (18)C12—C131.389 (2)
C7—O1—C1108.34 (10)O3—C7—C8110.03 (10)
C2—O2—H1O294 (2)O1—C7—C8110.31 (10)
C7—O3—C3111.17 (9)C9—C8—C13119.09 (13)
O1—C1—C2111.71 (11)C9—C8—C7121.10 (11)
O2—C2—C1109.53 (12)C13—C8—C7119.70 (12)
O2—C2—C3110.67 (11)C8—C9—C10120.44 (13)
C1—C2—C3110.83 (12)C11—C10—C9120.55 (15)
O3—C3—C3i107.96 (8)C10—C11—C12119.70 (15)
O3—C3—C2110.19 (10)C11—C12—C13120.32 (13)
C3i—C3—C2113.41 (14)C12—C13—C8119.89 (13)
O3—C7—O1109.11 (10)
C7—O1—C1—C258.34 (15)C1—O1—C7—C8170.47 (11)
O1—C1—C2—O2169.52 (11)O3—C7—C8—C917.58 (16)
O1—C1—C2—C347.14 (16)O1—C7—C8—C9138.00 (13)
C7—O3—C3—C3i179.70 (11)O3—C7—C8—C13166.24 (11)
C7—O3—C3—C255.36 (13)O1—C7—C8—C1345.81 (15)
O2—C2—C3—O3166.27 (11)C13—C8—C9—C100.3 (2)
C1—C2—C3—O344.54 (14)C7—C8—C9—C10175.86 (14)
O2—C2—C3—C3i72.58 (11)C8—C9—C10—C110.5 (3)
C1—C2—C3—C3i165.69 (14)C9—C10—C11—C121.1 (3)
C2—C3—C3i—C2i177.60 (12)C10—C11—C12—C130.9 (3)
C3—O3—C7—O168.30 (12)C11—C12—C13—C80.0 (2)
C3—O3—C7—C8170.56 (9)C9—C8—C13—C120.6 (2)
C1—O1—C7—O368.55 (13)C7—C8—C13—C12175.66 (12)
Symmetry code: (i) x+1, y, z.

Experimental details

Crystal data
Chemical formulaC20H22O6
Mr358.4
Crystal system, space groupMonoclinic, C2
Temperature (K)293
a, b, c (Å)17.472 (4), 4.9237 (10), 9.956 (2)
β (°) 94.08 (3)
V3)854.4 (3)
Z2
Radiation typeCu Kα
µ (mm1)0.85
Crystal size (mm)0.53 × 0.20 × 0.08
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ-scan
(North et al., 1968)
Tmin, Tmax0.668, 0.934
No. of measured, independent and
observed [I > 2σ (I)] reflections
4158, 1703, 1669
Rint0.027
(sin θ/λ)max1)0.626
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.033, 0.093, 0.93
No. of reflections1703
No. of parameters123
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.24, 0.17
Absolute structureFlack (1983)
Absolute structure parameter0.10 (17)

Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1996), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1997), SHELXTL.

Selected geometric parameters (Å, º) top
O1—C71.4179 (15)O3—C71.4076 (14)
O1—C11.4328 (18)O3—C31.4370 (15)
O2—C21.4273 (17)C3—C3i1.512 (2)
C7—O1—C1108.34 (10)C7—O3—C3111.17 (9)
C7—O1—C1—C258.34 (15)C1—C2—C3—C3i165.69 (14)
O1—C1—C2—O2169.52 (11)C2—C3—C3i—C2i177.60 (12)
O1—C1—C2—C347.14 (16)C3—O3—C7—O168.30 (12)
C7—O3—C3—C255.36 (13)C1—O1—C7—O368.55 (13)
C1—C2—C3—O344.54 (14)
Symmetry code: (i) x+1, y, z.
 

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