Two new heterocyclic [3.3.3.0^1,5]-propellanoid compounds: 2,8-dioxatricyclo[3.3.3.0^1,5]undecane-3,7-dione and a related dimer

2,8-Dioxatri­cyclo­[3.3.3.0^1,5]­un­decane-3,7-dione, C₉H₁₀O₄, (I), is the dilactone acylal of cyclo­pentanone-2,2-di­acetic acid. Both mol­ecules in the asymmetric unit have conformational chirality and differ principally in the flexing of the carbon ring, which produces a resolvable conformational disorder in one of the mol­ecules. Three intermolecular C—H...O close contacts exist. 7,7′-Oxybis(2,8-dioxatri­cyclo­[3.3.3.0^1,5]­undecan-3-one), C₁₈H₂₂O₇, (II), a racemate, lies on a C₂ axis and is a non-meso furan­osyl furan­oside dimer derived from the monoacid mono­aldehyde corresponding to (I). One intermolecular C—H...O close contact exists. Diminished intramolecular void space in these small propellanoids generates unusually high crystal density in both species, particularly (I).

S1. Comment

The propellanoids are an important class of fused polycyclic compounds in which three rings all share the same pair of adjacent tetrahedral atoms. A number of propellanoid natural products offer tempting and extraordinarily challenging synthetic targets (Corey & Cheng, 1989). Syntheses of propellanoids, despite their being widely ignored in historical accounts, actually reach back at least into the mid-1930 s, with reports of both carbocyclic (Fieser & Dunn, 1936) and heterocyclic examples (Diels & Friedrichsen, 1934; Fieser & Hershberg, 1936; Alder & Backendorf, 1938) arising from studies involving the Diels-Alder reaction. Syntheses specifically aimed at propellanoids per se first appeared in the mid-1960 s (Snatzke & Zanati, 1965; Nerdel et al., 1965; Altman et al., 1966; Thompson, 1966, 1968), and the name `propellanoid' and their recognition as a distinct class originated during this period (Altman et al., 1966). Since that time, numerous propellanoids have been reported, and our own investigations have produced several heterocyclic examples (Thompson, 1967; Zwege et al., 1999; Tsao et al., 2002), among them the two new compounds, (I) and (II), whose solid-state structures we now report. \sch

Fig. 1 shows the asymmetric unit for (I), which is the dilactone acylal of cyclopentanone-2,2-diacetic acid. In the subsequent discussion, primed numbering is used for the second of the two molecules in the asymmetric unit. Although the molecule contains a potential plane of symmetry, both (I) and (I') have conformational chirality, due to flexing of the various rings. The lactone rings depart only slightly from planarity, with atoms O3 and O7 removed 0.125 (4) and −0.013 (5) Å from, and atoms O3' and O7' tilted 0.015 (5) and 0.074 (4) Å out of, their respective ring planes. The carbon ring in both (I) and (I') adopts an envelope conformation. The dihedral angle C9'-C10'-C11' versus C9'-C1'-C5'-C11' is 37.0 (3)°, and removes atom C10' from the plane of the remaining C atoms of its ring by 0.524 (7) Å.

In component (I), this folded conformation for the carbon ring displays a disorder, corresponding to a flexing motion for atom C10, which is resolvable into two components. The predominant species in this 59 (2):41 (2) disorder (Fig. 1) has atom C10 lying over the C6—C7—O8 ring, 0.44 (2) Å out of the C9—C1—C5—C11 plane, with a dihedral angle of 30.4 (6)° between the latter plane and C9—C10—C11. In the 41% component, atom C10A lies over the other lactone ring (O2—C3—C4), −0.300 (16) Å out of the C9—C1—C5—C11 plane, with a dihedral angle of 22.3 (14)° between the latter plane and C9—C10A—C11. We have no information as to whether this disorder is a dynamic wagging or is static.

From studies of ring-chain tautomerism, it is known that γ-lactones are generally more stable than their δ homologs, so that acylglutaric acid cases similar to (I) tend to close spontaneously (Soffer et al., 1950; Valente et al., 1998), while in the six-membered counterparts, this equilibrium must often be driven to closure (Thompson, 1967).

Three significant intermolecular C—H···O close contacts were found in the packing of (I), namely from atom O3 to H6'B (2.47 Å), between atoms O7 and H4'A (2.55 Å), and between atoms O3' and H6B (2.58 Å). These distances all lie within the 2.7 Å range we often employ for non-bonded C—H···O packing interactions (Steiner, 1997). Based on compiled data for a large number of C—H···O contacts, Steiner & Desiraju (1998) found significant statistical directionality even as far out as 3.0 Å, and concluded that these are legitimately viewed as `weak hydrogen bonds', with a greater contribution to packing forces than simple van der Waals attractions.

Compound (II) is a furanosyl furanoside dimer derived from the monoacid monoaldehyde corresponding to (I). Fig. 2 shows its full structure, which consists of two asymmetric units related by a twofold axis through atom O7. Compound (II) is therefore non-meso, but is racemic overall. The atom-numbering scheme is identical for the two halves of the full molecule. As in (I), the lactone ring is the most planar and the carbon ring the least planar of the three, with the acetal ring significantly flexed as well. Within the asymmetric unit, the stereochemistry of the furanosyl acetal ring involves extension of atom O7 in the direction of the lactone ring and of atom H7 toward the carbon ring. Of all the diastereomers possible, compound (II), having stereochemically and chirally identical subunits, seems to have been formed in high predominance in this process, although another apparent isomer was found (gas chromatography/MS) in the mixture. The selectivity involved may have been due to displacement of equilibria by selective precipitation. One intermolecular C—H···O close contact was found within 2.7 Å, namely between atoms O2 and H11B (2.59 Å).

The essential characteristic core of two attached quaternary sites in propellanoids represents a region of high atom- and ring-density. Small members of this class consequently have less void space and potentially higher crystal density than other comparable aliphatic compounds, as is the case for both (I) and (II), whose crystal densities are 1.413 and 1.382 Mg m⁻³, respectively. A similar but even higher crystal density (1.452 Mg m⁻³) is seen in the transoid analog of (I) (Tsao et al., 2002). This density potential may not be realised in cases where the packing is dominated by hydrogen-bonding forces, which can actually prevent the closest possible (van der Waals) packing. Thus, the C₁₃ propellanoid keto lactam described by Zwege et al. (1999), the packing of which is determined by hydrogen bonding in both its reported crystalline modifications, has crystal densities of 1.229 and 1.275 Mg m⁻³. These values are entirely normal for aliphatic species, but markedly lower than those found for (I) and (II), in which hydrogen bonding is absent.

S2. Experimental

Compound (I) was synthesized from indane by a series of steps that included lithium-ammonia reduction and selective epoxidation (Giovanni & Wegmüller, 1958), acid-catalyzed rearrangement, and oxidative alkene cleavage (Carlsen et al., 1981). Compound (II) is a by-product, arising from incomplete oxidation. Both (I) and (II) are previously unreported, although their dioxatricyclic ring system is known (Mehta et al., 1987).

The CHCl₃ IR spectrum of (I) displays a single intense C═O peak at 1797 cm^{−1. 1}H NMR (δ, p.p.m.): 2.80 (2H, d, J = 19.17 Hz), 2.77 (2H, d, J = 19.16 Hz), 2.23 (2H, t, J = 7.12 Hz), 1.99 (2H, t, J = 6.57 Hz), 1.86 (2H, quintet, J = 6.57 and 7.12 Hz). ¹³C NMR (δ, p.p.m.): 173.42, 122.53, 49.61, 42.73. 40.04, 36.81, 23.68. Major EI/MS peaks appear at m/e 182 (M+, 0.7%), 154 (9.0), 110 (91.9), 82 (81.6), 67 (100), 55 (76.1) and 39 (53.6). Crystals of (I) (m.p. 379 K) suitable for X-ray analysis were obtained from CH₂Cl₂.

The KBr IR spectrum of (II) displays a single C═O peak at 1786 cm^{−1. 1}H NMR (δ, p.p.m.): 5.62 (2H, d, J = 4.58 Hz), 2.80 (2H, d, J = 18.92 Hz), 2.66 (2H, d, J = 18.62 Hz), 2.20 (2H, m), 2.14 (2H, d J = 13.43 Hz), 2.02–1.94 (4H, m, including 1.86, 2H, dd, J = 13.43 and 4.58 Hz), 1.86 (4H, m), 1.70 (4H, m). ¹³C NMR (δ, p.p.m.): 176.74, 127.61, 103.29, 53.26, 45.86. 44.98, 40.45, 37.02, 24.64. Major EI/MS peaks appear at m/e 278 (1.2%), 167 (100), 149 (16.4), 139 (10.8), 125 (20.6), 110 (15.0), 95 (10.1), 67 (9.3) and 55 (12.7). Crystals of (II) (m.p. 465 K) suitable for X-ray analysis were obtained from methyl tert-butyl ether/CH₂Cl₂ (Ratio?).

S3. Refinement

All H atoms for (I) and (II) were found in electron-density difference maps, but were placed in calculated positions (C—H distances of 0.97 Å for methylene H atoms and 0.98 Å for methine H atoms) and allowed to refine as riding models on their respective C atoms, with U_iso(H) = 1.2U_eq(C). Atom C10 of (I) exhibited significant disordering [ratio 0.59:0.41 (2)].

Computing details

For both compounds, data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The asymmetric unit of (I) and its numbering. The numbering scheme for the second molecule in the asymmetric unit has primed atom labels. Solid bonds show the major component in one ring and open bonds the minor [0.59 (2):0.41 (2)]. Displacement ellipsoids are set at the 15% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. Compound (II) and its numbering. The molecule consists of two asymmetric units related by a twofold axis through atom O7. Displacement ellipsoids are set at the 20% probability level and H atoms are shown as small spheres of arbitrary radii.

(I) 2,8-Dioxatricyclo[3.3.3.0^1,5]undecane-3,7-dione

Crystal data

C9H10O4	Dx = 1.413 Mg m^−3
Mr = 182.17	Melting point: 379 K
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.697 (3) Å	Cell parameters from 27 reflections
b = 12.240 (5) Å	θ = 3.8–8.8°
c = 11.509 (4) Å	µ = 0.11 mm^−1
β = 106.79 (2)°	T = 296 K
V = 1712.4 (10) Å^3	Square tablet, yellow
Z = 8	0.48 × 0.36 × 0.24 mm
F(000) = 768

Data collection

Siemens P4 diffractometer	1898 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.017
Graphite monochromator	θmax = 25.0°, θmin = 2.4°
2θ/θ scans	h = −15→14
Absorption correction: analytical (SHELXTL; Sheldrick, 1997)	k = −14→1
Tmin = 0.94, Tmax = 0.96	l = −1→13
3839 measured reflections	3 standard reflections every 97 reflections
3008 independent reflections	intensity decay: variation <1.0%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.055	H-atom parameters constrained
wR(F^2) = 0.158	w = 1/[σ^2(Fo^2) + (0.0611P)^2 + 0.6938P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
3008 reflections	Δρmax = 0.27 e Å^−3
243 parameters	Δρmin = −0.17 e Å^−3
0 restraints	Extinction correction: SHELXTL (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.022 (2)

Special details

Experimental. Crystal mounted on glass fiber using cyanoacrylate cement

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.8734 (2)	0.6685 (2)	0.0381 (2)	0.0586 (7)
O2	0.97789 (16)	0.62141 (15)	0.05275 (18)	0.0649 (6)
O3	1.12482 (19)	0.57662 (19)	0.2010 (2)	0.0901 (7)
C3	1.0336 (3)	0.6111 (2)	0.1718 (3)	0.0631 (7)
C4	0.9644 (2)	0.6465 (3)	0.2485 (3)	0.0680 (8)
H4A	1.0037	0.6989	0.3088	0.082*
H4B	0.9446	0.5844	0.2902	0.082*
C5	0.8629 (2)	0.6980 (2)	0.1649 (2)	0.0506 (6)
C6	0.8635 (2)	0.8211 (2)	0.1637 (3)	0.0645 (8)
H6A	0.7974	0.8495	0.1791	0.077*
H6B	0.9270	0.8490	0.2255	0.077*
O7	0.8671 (2)	0.9431 (2)	0.0000 (3)	0.1242 (11)
C7	0.8679 (3)	0.8538 (3)	0.0411 (3)	0.0777 (10)
O8	0.87170 (18)	0.7662 (2)	−0.02718 (18)	0.0807 (7)
C9	0.7788 (3)	0.5961 (3)	−0.0246 (4)	0.0985 (12)
H9A	0.8000	0.5198	−0.0166	0.118*
H9B	0.7507	0.6143	−0.1101	0.118*
C10	0.6944 (7)	0.6206 (11)	0.0419 (6)	0.085 (3)	0.59 (2)
H10A	0.6484	0.6815	0.0039	0.102*	0.59 (2)
H10B	0.6477	0.5575	0.0397	0.102*	0.59 (2)
C10A	0.7274 (7)	0.5698 (11)	0.0618 (6)	0.090 (4)	0.41 (2)
H10E	0.7498	0.4970	0.0923	0.107*	0.41 (2)
H10F	0.6485	0.5688	0.0243	0.107*	0.41 (2)
C11	0.7537 (3)	0.6472 (3)	0.1657 (3)	0.0786 (9)
H11A	0.7664	0.5818	0.2153	0.094*
H11B	0.7117	0.6984	0.1990	0.094*
C1'	0.6211 (2)	0.3713 (3)	0.3302 (2)	0.0626 (8)
O2'	0.69620 (18)	0.3770 (2)	0.26048 (19)	0.0854 (7)
O3'	0.8705 (2)	0.3466 (2)	0.2786 (3)	0.1194 (10)
C3'	0.7978 (3)	0.3440 (3)	0.3246 (3)	0.0762 (9)
C4'	0.7971 (2)	0.3069 (3)	0.4451 (3)	0.0752 (9)
H4'A	0.8484	0.3495	0.5074	0.090*
H4'B	0.8184	0.2306	0.4563	0.090*
C5'	0.6815 (2)	0.3217 (2)	0.4533 (2)	0.0556 (7)
C6'	0.6683 (3)	0.4093 (3)	0.5407 (3)	0.0714 (9)
H6'A	0.6202	0.3841	0.5870	0.086*
H6'B	0.7391	0.4279	0.5967	0.086*
O7'	0.6025 (2)	0.5935 (2)	0.5001 (3)	0.1211 (11)
C7'	0.6204 (2)	0.5042 (3)	0.4671 (4)	0.0758 (9)
O8'	0.59176 (17)	0.47929 (19)	0.3478 (2)	0.0827 (7)
C9'	0.5256 (3)	0.2979 (4)	0.2718 (3)	0.0935 (12)
H9'A	0.4585	0.3240	0.2865	0.112*
H9'B	0.5144	0.2925	0.1850	0.112*
C10'	0.5600 (4)	0.1920 (4)	0.3323 (5)	0.1297 (17)
H10C	0.4963	0.1467	0.3278	0.156*
H10D	0.6077	0.1535	0.2938	0.156*
C11'	0.6177 (4)	0.2165 (3)	0.4566 (4)	0.0990 (12)
H11C	0.6676	0.1576	0.4925	0.119*
H11D	0.5663	0.2268	0.5037	0.119*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0563 (16)	0.0664 (18)	0.0557 (16)	0.0044 (13)	0.0206 (13)	−0.0052 (14)
O2	0.0651 (12)	0.0674 (12)	0.0685 (13)	0.0086 (10)	0.0293 (10)	−0.0074 (10)
O3	0.0681 (14)	0.0922 (17)	0.1095 (18)	0.0319 (12)	0.0250 (12)	0.0122 (14)
C3	0.0633 (18)	0.0527 (16)	0.074 (2)	0.0088 (14)	0.0218 (15)	0.0080 (14)
C4	0.0679 (18)	0.077 (2)	0.0612 (17)	0.0139 (15)	0.0229 (14)	0.0159 (15)
C5	0.0506 (14)	0.0559 (15)	0.0489 (14)	−0.0004 (12)	0.0199 (11)	0.0001 (12)
C6	0.0676 (18)	0.0611 (18)	0.0721 (19)	0.0087 (14)	0.0315 (15)	−0.0008 (15)
O7	0.145 (3)	0.0855 (18)	0.176 (3)	0.0422 (16)	0.100 (2)	0.0645 (19)
C7	0.074 (2)	0.071 (2)	0.103 (3)	0.0252 (16)	0.0497 (19)	0.030 (2)
O8	0.0946 (16)	0.0955 (17)	0.0612 (13)	0.0282 (13)	0.0373 (12)	0.0212 (12)
C9	0.076 (2)	0.117 (3)	0.098 (3)	−0.015 (2)	0.017 (2)	−0.046 (2)
C10	0.064 (4)	0.095 (6)	0.093 (5)	−0.019 (4)	0.018 (3)	−0.011 (4)
C10A	0.103 (8)	0.076 (7)	0.086 (7)	−0.043 (6)	0.022 (6)	0.003 (5)
C11	0.068 (2)	0.081 (2)	0.097 (2)	−0.0159 (17)	0.0396 (18)	−0.0055 (19)
C1'	0.0528 (16)	0.081 (2)	0.0556 (17)	0.0057 (14)	0.0188 (13)	0.0081 (15)
O2'	0.0794 (15)	0.1149 (19)	0.0723 (14)	0.0173 (13)	0.0386 (12)	0.0302 (13)
O3'	0.1009 (19)	0.111 (2)	0.183 (3)	0.0148 (16)	0.098 (2)	0.020 (2)
C3'	0.067 (2)	0.0644 (19)	0.111 (3)	0.0059 (15)	0.047 (2)	0.0065 (19)
C4'	0.0689 (19)	0.0682 (19)	0.083 (2)	0.0198 (16)	0.0126 (16)	−0.0009 (17)
C5'	0.0574 (16)	0.0545 (16)	0.0519 (15)	−0.0035 (12)	0.0112 (12)	0.0049 (13)
C6'	0.0601 (17)	0.093 (2)	0.0606 (18)	−0.0106 (16)	0.0172 (14)	−0.0136 (17)
O7'	0.0827 (17)	0.0784 (18)	0.213 (3)	−0.0035 (13)	0.060 (2)	−0.0432 (19)
C7'	0.0465 (16)	0.068 (2)	0.118 (3)	−0.0040 (15)	0.0303 (18)	−0.009 (2)
O8'	0.0721 (14)	0.0809 (16)	0.0960 (18)	0.0226 (11)	0.0255 (12)	0.0270 (13)
C9'	0.064 (2)	0.152 (4)	0.060 (2)	−0.010 (2)	0.0108 (16)	−0.023 (2)
C10'	0.130 (4)	0.122 (4)	0.136 (4)	−0.058 (3)	0.037 (3)	−0.041 (3)
C11'	0.139 (3)	0.071 (2)	0.093 (3)	−0.032 (2)	0.043 (2)	0.0000 (19)

Geometric parameters (Å, º)

C1—O8	1.409 (3)	C11—H11A	0.9700
C1—O2	1.411 (3)	C11—H11B	0.9700
C1—C9	1.500 (4)	C1'—O8'	1.404 (4)
C1—C5	1.547 (4)	C1'—O2'	1.414 (3)
O2—C3	1.354 (3)	C1'—C9'	1.502 (4)
O3—C3	1.186 (3)	C1'—C5'	1.528 (4)
C3—C4	1.480 (4)	O2'—C3'	1.350 (4)
C4—C5	1.505 (4)	O3'—C3'	1.190 (4)
C4—H4A	0.9700	C3'—C4'	1.462 (4)
C4—H4B	0.9700	C4'—C5'	1.509 (4)
C5—C6	1.506 (4)	C4'—H4'A	0.9700
C5—C11	1.522 (4)	C4'—H4'B	0.9700
C6—C7	1.483 (4)	C5'—C6'	1.512 (4)
C6—H6A	0.9700	C5'—C11'	1.528 (4)
C6—H6B	0.9700	C6'—C7'	1.463 (5)
O7—C7	1.190 (4)	C6'—H6'A	0.9700
C7—O8	1.338 (4)	C6'—H6'B	0.9700
C9—C10A	1.376 (6)	O7'—C7'	1.200 (4)
C9—C10	1.515 (8)	C7'—O8'	1.350 (4)
C9—H9A	0.9700	C9'—C10'	1.476 (6)
C9—H9B	0.9700	C9'—H9'A	0.9700
C10—C11	1.444 (6)	C9'—H9'B	0.9700
C10—H10A	0.9700	C10'—C11'	1.438 (5)
C10—H10B	0.9700	C10'—H10C	0.9700
C10A—C11	1.486 (7)	C10'—H10D	0.9700
C10A—H10E	0.9699	C11'—H11C	0.9700
C10A—H10F	0.9700	C11'—H11D	0.9700
O8—C1—O2	106.3 (2)	C10A—C11—H11A	84.7
O8—C1—C9	111.0 (3)	C5—C11—H11A	110.2
O2—C1—C9	114.3 (3)	C10—C11—H11B	110.2
O8—C1—C5	108.2 (2)	C10A—C11—H11B	135.0
O2—C1—C5	108.5 (2)	C5—C11—H11B	110.2
C9—C1—C5	108.4 (2)	H11A—C11—H11B	108.5
C3—O2—C1	111.0 (2)	O8'—C1'—O2'	106.6 (2)
O3—C3—O2	120.2 (3)	O8'—C1'—C9'	114.5 (3)
O3—C3—C4	129.4 (3)	O2'—C1'—C9'	111.4 (3)
O2—C3—C4	110.5 (2)	O8'—C1'—C5'	108.8 (2)
C3—C4—C5	106.7 (2)	O2'—C1'—C5'	107.8 (2)
C3—C4—H4A	110.4	C9'—C1'—C5'	107.6 (3)
C5—C4—H4A	110.4	C3'—O2'—C1'	111.7 (2)
C3—C4—H4B	110.4	O3'—C3'—O2'	119.4 (3)
C5—C4—H4B	110.4	O3'—C3'—C4'	130.4 (3)
H4A—C4—H4B	108.6	O2'—C3'—C4'	110.2 (3)
C4—C5—C6	114.8 (2)	C3'—C4'—C5'	107.1 (2)
C4—C5—C11	116.0 (2)	C3'—C4'—H4'A	110.3
C6—C5—C11	114.5 (2)	C5'—C4'—H4'A	110.3
C4—C5—C1	102.4 (2)	C3'—C4'—H4'B	110.3
C6—C5—C1	102.9 (2)	C5'—C4'—H4'B	110.3
C11—C5—C1	103.7 (2)	H4'A—C4'—H4'B	108.5
C7—C6—C5	106.2 (2)	C4'—C5'—C6'	115.1 (2)
C7—C6—H6A	110.5	C4'—C5'—C11'	115.6 (3)
C5—C6—H6A	110.5	C6'—C5'—C11'	114.8 (3)
C7—C6—H6B	110.5	C4'—C5'—C1'	103.1 (2)
C5—C6—H6B	110.5	C6'—C5'—C1'	102.3 (2)
H6A—C6—H6B	108.7	C11'—C5'—C1'	103.3 (2)
O7—C7—O8	120.0 (3)	C7'—C6'—C5'	106.6 (3)
O7—C7—C6	128.9 (4)	C7'—C6'—H6'A	110.4
O8—C7—C6	111.2 (3)	C5'—C6'—H6'A	110.4
C7—O8—C1	111.4 (2)	C7'—C6'—H6'B	110.4
C10A—C9—C1	105.8 (3)	C5'—C6'—H6'B	110.4
C1—C9—C10	103.1 (3)	H6'A—C6'—H6'B	108.6
C10A—C9—H9A	83.3	O7'—C7'—O8'	120.5 (4)
C1—C9—H9A	111.2	O7'—C7'—C6'	128.7 (4)
C10—C9—H9A	111.2	O8'—C7'—C6'	110.7 (3)
C10A—C9—H9B	132.5	C7'—O8'—C1'	110.8 (2)
C1—C9—H9B	111.2	C10'—C9'—C1'	102.9 (3)
C10—C9—H9B	111.2	C10'—C9'—H9'A	111.2
H9A—C9—H9B	109.1	C1'—C9'—H9'A	111.2
C11—C10—C9	107.4 (6)	C10'—C9'—H9'B	111.2
C11—C10—H10A	110.2	C1'—C9'—H9'B	111.2
C9—C10—H10A	110.2	H9'A—C9'—H9'B	109.1
C11—C10—H10B	110.2	C11'—C10'—C9'	106.4 (4)
C9—C10—H10B	110.2	C11'—C10'—H10C	110.4
H10A—C10—H10B	108.5	C9'—C10'—H10C	110.4
C9—C10A—C11	112.9 (5)	C11'—C10'—H10D	110.4
C9—C10A—H10E	109.1	C9'—C10'—H10D	110.4
C11—C10A—H10E	108.7	H10C—C10'—H10D	108.6
C9—C10A—H10F	109.0	C10'—C11'—C5'	105.8 (3)
C11—C10A—H10F	109.3	C10'—C11'—H11C	110.6
H10E—C10A—H10F	107.8	C5'—C11'—H11C	110.6
C10—C11—C5	107.6 (3)	C10'—C11'—H11D	110.6
C10A—C11—C5	104.4 (3)	C5'—C11'—H11D	110.6
C10—C11—H11A	110.2	H11C—C11'—H11D	108.7
O8—C1—O2—C3	119.5 (2)	C4—C5—C11—C10	−126.5 (7)
C9—C1—O2—C3	−117.8 (3)	C6—C5—C11—C10	96.2 (7)
C5—C1—O2—C3	3.3 (3)	C1—C5—C11—C10	−15.2 (7)
C1—O2—C3—O3	−177.2 (3)	C4—C5—C11—C10A	−95.9 (6)
C1—O2—C3—C4	3.4 (3)	C6—C5—C11—C10A	126.8 (6)
O3—C3—C4—C5	171.9 (3)	C1—C5—C11—C10A	15.4 (6)
O2—C3—C4—C5	−8.8 (3)	O8'—C1'—O2'—C3'	113.1 (3)
C3—C4—C5—C6	−100.7 (3)	C9'—C1'—O2'—C3'	−121.4 (3)
C3—C4—C5—C11	122.1 (3)	C5'—C1'—O2'—C3'	−3.6 (3)
C3—C4—C5—C1	10.0 (3)	C1'—O2'—C3'—O3'	−178.4 (3)
O8—C1—C5—C4	−123.2 (2)	C1'—O2'—C3'—C4'	3.0 (4)
O2—C1—C5—C4	−8.3 (3)	O3'—C3'—C4'—C5'	−179.5 (4)
C9—C1—C5—C4	116.3 (3)	O2'—C3'—C4'—C5'	−1.1 (4)
O8—C1—C5—C6	−3.8 (3)	C3'—C4'—C5'—C6'	−111.6 (3)
O2—C1—C5—C6	111.1 (2)	C3'—C4'—C5'—C11'	110.9 (3)
C9—C1—C5—C6	−124.3 (3)	C3'—C4'—C5'—C1'	−1.1 (3)
O8—C1—C5—C11	115.8 (2)	O8'—C1'—C5'—C4'	−112.5 (2)
O2—C1—C5—C11	−129.3 (2)	O2'—C1'—C5'—C4'	2.7 (3)
C9—C1—C5—C11	−4.6 (3)	C9'—C1'—C5'—C4'	123.0 (3)
C4—C5—C6—C7	113.2 (3)	O8'—C1'—C5'—C6'	7.3 (3)
C11—C5—C6—C7	−109.0 (3)	O2'—C1'—C5'—C6'	122.5 (3)
C1—C5—C6—C7	2.8 (3)	C9'—C1'—C5'—C6'	−117.3 (3)
C5—C6—C7—O7	178.0 (3)	O8'—C1'—C5'—C11'	126.8 (3)
C5—C6—C7—O8	−0.9 (3)	O2'—C1'—C5'—C11'	−118.0 (3)
O7—C7—O8—C1	179.3 (3)	C9'—C1'—C5'—C11'	2.3 (3)
C6—C7—O8—C1	−1.6 (3)	C4'—C5'—C6'—C7'	102.5 (3)
O2—C1—O8—C7	−112.8 (3)	C11'—C5'—C6'—C7'	−119.6 (3)
C9—C1—O8—C7	122.4 (3)	C1'—C5'—C6'—C7'	−8.5 (3)
C5—C1—O8—C7	3.5 (3)	C5'—C6'—C7'—O7'	−175.0 (3)
O8—C1—C9—C10A	−127.7 (7)	C5'—C6'—C7'—O8'	7.4 (3)
O2—C1—C9—C10A	112.2 (7)	O7'—C7'—O8'—C1'	179.5 (3)
C5—C1—C9—C10A	−9.0 (8)	C6'—C7'—O8'—C1'	−2.6 (3)
O8—C1—C9—C10	−97.3 (6)	O2'—C1'—O8'—C7'	−119.2 (2)
O2—C1—C9—C10	142.5 (6)	C9'—C1'—O8'—C7'	117.2 (3)
C5—C1—C9—C10	21.4 (6)	C5'—C1'—O8'—C7'	−3.2 (3)
C10A—C9—C10—C11	67.6 (7)	O8'—C1'—C9'—C10'	−144.3 (3)
C1—C9—C10—C11	−31.4 (9)	O2'—C1'—C9'—C10'	94.7 (3)
C1—C9—C10A—C11	20.2 (11)	C5'—C1'—C9'—C10'	−23.3 (4)
C10—C9—C10A—C11	−68.5 (9)	C1'—C9'—C10'—C11'	37.0 (4)
C9—C10—C11—C10A	−58.7 (7)	C9'—C10'—C11'—C5'	−36.4 (5)
C9—C10—C11—C5	29.5 (9)	C4'—C5'—C11'—C10'	−91.4 (4)
C9—C10A—C11—C10	77.1 (9)	C6'—C5'—C11'—C10'	131.0 (4)
C9—C10A—C11—C5	−23.3 (11)	C1'—C5'—C11'—C10'	20.4 (4)

(II) 7,7'-Oxybis(2,8-dioxatricyclo[3.3.3.0^1,5]undecan-3-one)

Crystal data

C18H22O7	Dx = 1.382 Mg m^−3
Mr = 350.36	Melting point: 465 K
Orthorhombic, Fdd2	Mo Kα radiation, λ = 0.71073 Å
a = 11.571 (5) Å	Cell parameters from 20 reflections
b = 27.069 (10) Å	θ = 2.7–6.2°
c = 10.754 (5) Å	µ = 0.11 mm^−1
V = 3368 (2) Å^3	T = 296 K
Z = 8	Parallelepiped, colourless
F(000) = 1488	0.44 × 0.38 × 0.12 mm

Data collection

Siemens P4 diffractometer	463 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.061
Graphite monochromator	θmax = 25.0°, θmin = 2.7°
2θ/θ scans	h = −13→13
Absorption correction: numerical (SHELXTL; Sheldrick, 1997)	k = −32→32
Tmin = 0.96, Tmax = 0.99	l = −12→12
1578 measured reflections	3 standard reflections every 97 reflections
789 independent reflections	intensity decay: variation <1.6%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.082	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0143P)^2] where P = (Fo^2 + 2Fc^2)/3
789 reflections	(Δ/σ)max < 0.001
114 parameters	Δρmax = 0.11 e Å^−3
1 restraint	Δρmin = −0.13 e Å^−3

Special details

Experimental. Crystal mounted on glass fiber using cyanoacrylate cement

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 (Ų)

	x	y	z	Uiso*/Ueq
O2	0.6380 (3)	0.35079 (12)	0.5720 (3)	0.0636 (10)
O3	0.7379 (3)	0.36642 (13)	0.7441 (4)	0.0851 (13)
O7	0.7500	0.2500	0.5725 (4)	0.0586 (13)
O8	0.6108 (3)	0.28387 (14)	0.4388 (3)	0.0679 (11)
C1	0.5562 (5)	0.31514 (18)	0.5266 (5)	0.0539 (13)
C3	0.6640 (5)	0.34280 (19)	0.6933 (5)	0.0582 (15)
C4	0.5898 (4)	0.30279 (16)	0.7460 (4)	0.0560 (13)
C5	0.5182 (4)	0.28239 (17)	0.6385 (5)	0.0517 (13)
C6	0.5524 (5)	0.23048 (18)	0.5958 (5)	0.0632 (16)
C7	0.6472 (5)	0.24046 (18)	0.5046 (6)	0.0662 (15)
C9	0.4486 (4)	0.3397 (2)	0.4729 (6)	0.0738 (18)
C10	0.3504 (5)	0.3049 (2)	0.5156 (6)	0.0795 (18)
C11	0.3872 (5)	0.2900 (2)	0.6461 (5)	0.0710 (17)
H4A	0.5397	0.3159	0.8104	0.067*
H4B	0.6373	0.2769	0.7820	0.067*
H6A	0.5799	0.2107	0.6650	0.076*
H6B	0.4880	0.2137	0.5565	0.076*
H7B	0.6575	0.2125	0.4477	0.079*
H9A	0.4525	0.3415	0.3830	0.089*
H9B	0.4383	0.3727	0.5063	0.089*
H10A	0.2767	0.3220	0.5169	0.095*
H10B	0.3445	0.2763	0.4616	0.095*
H11A	0.3489	0.2597	0.6712	0.085*
H11B	0.3684	0.3157	0.7055	0.085*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.068 (2)	0.054 (2)	0.069 (3)	−0.0108 (19)	−0.014 (2)	0.012 (2)
O3	0.086 (3)	0.078 (3)	0.092 (3)	−0.023 (2)	−0.028 (3)	−0.014 (2)
O7	0.059 (3)	0.068 (3)	0.049 (3)	0.008 (3)	0.000	0.000
O8	0.075 (3)	0.082 (3)	0.047 (2)	0.011 (2)	−0.003 (2)	0.001 (2)
C1	0.061 (3)	0.050 (3)	0.051 (3)	0.001 (3)	−0.012 (3)	0.002 (3)
C3	0.062 (4)	0.056 (4)	0.057 (4)	0.007 (3)	−0.010 (3)	−0.006 (3)
C4	0.066 (3)	0.051 (3)	0.051 (3)	−0.003 (3)	0.000 (3)	−0.001 (3)
C5	0.055 (3)	0.045 (3)	0.056 (3)	−0.006 (3)	0.001 (3)	−0.003 (3)
C6	0.070 (4)	0.055 (4)	0.065 (4)	−0.005 (3)	−0.005 (3)	−0.002 (3)
C7	0.085 (4)	0.054 (3)	0.060 (4)	0.012 (3)	−0.010 (4)	−0.013 (3)
C9	0.068 (4)	0.075 (4)	0.079 (5)	0.003 (3)	−0.017 (4)	0.008 (3)
C10	0.065 (4)	0.089 (4)	0.085 (5)	0.007 (3)	−0.022 (4)	−0.015 (4)
C11	0.067 (4)	0.072 (4)	0.074 (4)	−0.007 (3)	0.009 (4)	−0.016 (3)

Geometric parameters (Å, º)

O2—C3	1.356 (6)	C9—C10	1.545 (7)
O2—C1	1.437 (6)	C10—C11	1.521 (7)
O3—C3	1.199 (5)	C4—H4A	0.9700
O7—C7	1.419 (5)	C4—H4B	0.9700
O7—C7^i	1.419 (5)	C6—H6A	0.9700
O8—C1	1.417 (6)	C6—H6B	0.9700
O8—C7	1.435 (6)	C7—H7B	0.9800
C1—C9	1.525 (6)	C9—H9A	0.9700
C1—C5	1.558 (7)	C9—H9B	0.9700
C3—C4	1.494 (6)	C10—H10A	0.9700
C4—C5	1.526 (6)	C10—H10B	0.9700
C5—C6	1.531 (6)	C11—H11A	0.9700
C5—C11	1.531 (6)	C11—H11B	0.9700
C6—C7	1.496 (7)
C3—O2—C1	111.4 (4)	C5—C4—H4A	110.4
C7—O7—C7^i	118.1 (6)	C3—C4—H4B	110.4
C1—O8—C7	106.9 (4)	C5—C4—H4B	110.4
O8—C1—O2	109.5 (4)	H4A—C4—H4B	108.6
O8—C1—C9	111.8 (5)	C7—C6—H6A	111.2
O2—C1—C9	111.9 (4)	C5—C6—H6A	111.2
O8—C1—C5	107.5 (4)	C7—C6—H6B	111.2
O2—C1—C5	107.8 (4)	C5—C6—H6B	111.2
C9—C1—C5	108.1 (4)	H6A—C6—H6B	109.1
O3—C3—O2	120.8 (5)	O7—C7—H7B	111.1
O3—C3—C4	128.5 (5)	O8—C7—H7B	111.1
O2—C3—C4	110.7 (5)	C6—C7—H7B	111.1
C3—C4—C5	106.6 (4)	C1—C9—H9A	111.2
C4—C5—C6	114.8 (4)	C10—C9—H9A	111.2
C4—C5—C11	116.6 (5)	C1—C9—H9B	111.2
C6—C5—C11	113.3 (4)	C10—C9—H9B	111.2
C4—C5—C1	103.1 (3)	H9A—C9—H9B	109.1
C6—C5—C1	102.6 (4)	C11—C10—H10A	111.1
C11—C5—C1	104.1 (4)	C9—C10—H10A	111.1
C7—C6—C5	102.7 (4)	C11—C10—H10B	111.1
O7—C7—O8	110.5 (4)	C9—C10—H10B	111.1
O7—C7—C6	108.1 (5)	H10A—C10—H10B	109.1
O8—C7—C6	104.9 (4)	C10—C11—H11A	110.7
C1—C9—C10	102.8 (4)	C5—C11—H11A	110.7
C11—C10—C9	103.3 (5)	C10—C11—H11B	110.7
C10—C11—C5	105.3 (5)	C5—C11—H11B	110.7
C3—C4—H4A	110.4	H11A—C11—H11B	108.8
C7—O8—C1—O2	95.9 (5)	O2—C1—C5—C11	120.5 (4)
C7—O8—C1—C9	−139.5 (4)	C9—C1—C5—C11	−0.6 (5)
C7—O8—C1—C5	−21.0 (5)	C4—C5—C6—C7	−86.2 (5)
C3—O2—C1—O8	−111.7 (4)	C11—C5—C6—C7	136.4 (5)
C3—O2—C1—C9	123.7 (5)	C1—C5—C6—C7	24.8 (5)
C3—O2—C1—C5	5.0 (5)	C7^i—O7—C7—O8	−67.0 (4)
C1—O2—C3—O3	173.9 (5)	C7^i—O7—C7—C6	178.7 (4)
C1—O2—C3—C4	−6.2 (5)	C1—O8—C7—O7	−78.4 (5)
O3—C3—C4—C5	−175.2 (5)	C1—O8—C7—C6	37.8 (5)
O2—C3—C4—C5	4.9 (5)	C5—C6—C7—O7	79.2 (5)
C3—C4—C5—C6	109.0 (4)	C5—C6—C7—O8	−38.7 (5)
C3—C4—C5—C11	−115.1 (5)	O8—C1—C9—C10	95.0 (5)
C3—C4—C5—C1	−1.7 (5)	O2—C1—C9—C10	−141.7 (5)
O8—C1—C5—C4	116.3 (4)	C5—C1—C9—C10	−23.1 (6)
O2—C1—C5—C4	−1.7 (5)	C1—C9—C10—C11	38.3 (5)
C9—C1—C5—C4	−122.8 (5)	C9—C10—C11—C5	−39.7 (5)
O8—C1—C5—C6	−3.3 (5)	C4—C5—C11—C10	137.6 (4)
O2—C1—C5—C6	−121.2 (4)	C6—C5—C11—C10	−85.8 (5)
C9—C1—C5—C6	117.6 (5)	C1—C5—C11—C10	24.8 (5)
O8—C1—C5—C11	−121.5 (4)

Symmetry code: (i) −x+3/2, −y+1/2, z.