A novel chelatofore functionalized spiro­pyran of the 2-oxaindane series

A novel chelatofore functionalized spiro­pyran of the 2-oxaindane series, namely 8-formyl-7-hydr­oxy-3′,3′-dimethyl­spiro­[2H-chromene-2,1′(3′H)-2-benzofuran], C₁₉H₁₆O₄, is re­ported. In the crystalline state, dimers are formed as a result of the π–π stacking of aromatic groups of the 2H-chromene part of the mol­ecule and C—H...O inter­actions. The C_spiro—O bond length in the pyran ring is 1.4558 (10) Å, which is longer than or equal to the bond length in thermo- and photochromic 2-oxaindane spiro­pyrans synthesized previously, except for the 7,8-benzo/6-NO₂ derivative, in which this bond length is 1.465 (2) Å.

S1. Comment

Heterocyclic spiropyrans of different series are prospective candidates for substances possessing photo- (Bertleson, 1971; Durr, 1990), electro- (Monk et al., 1995) and thermochromic (Bercovic et al., 2000) properties as a result of reversible opening–closing reactions of the pyran ring under the effect of light, external electric field or heat, respectively. The number of studies of this class of substances is steadily growing, and their syntheses (Lukyanov & Lukyanova, 2005) and properties (Minkin, 2004) have been thoroughly summarized and reviewed. One of the challenging goals in this field is to develop synthetic methods of functionalization of molecules with photochromic properties (e.g. spiropyran class) by incorporating into their structure chelating groups in order to prepare coordination compounds with transition and f-metal ions; such an approach will allow us to study the possibility of tuning the photochromic properties of the spiropyran moiety by complex formation or of obtaining promising hybrid photo- and magnetoactive substances (Bulanov et al., 2002, 2003).

We present here the crystal structure of a novel spiropyran of the 2-oxaindane series, 8-formyl-7-hydroxy-3',3'-dimethylspiro[2H-chromene-2,1'(3'H)-2-benzofuran], (I), which is functionalized by chelatophore centres (with the hydroxy group in a position ortho to the formyl group) for further synthesis of useful ligands (Schiff bases, hydrazones etc.). The numbering of the atoms for (I) is shown in Fig. 1 and selected geometric parameters are given in Table 1.

The title compound crystallizes in the closed spiro form. The main features of the molecular structure are similar to spiropyrans studied so far. In the molecule of (I), the 2H-chromene and oxaindane fragments are nearly orthogonal to each other [the angle between the least squares planes is 85.74 (3)°]. The pyran and oxaindane rings joined at spirocenter C2 are substantially nonplanar. The oxaindane moiety is in the `envelope' conformation, with atom O2' lying 0.123 (1) Å out of the least sqaures plane defined by the other eight non-H atoms of this fragment [the largest deviation from the least squares plane within this group is 0.026 (1) Å] as a result of bending along the C2···C1' line. In the substituted benzopyran fragment, 11 atoms (all except the spiroatom C2 and the pyran atom O1) are located in one plane; the largest deviation is 0.033 (1) Å. The pyran ring is distorted as a result of a small (for a six-membered ring) bond angle at the sp³-hybridized atom C2 [112.44 (7)°]. Atoms O1 and C2 deviate on opposite sides of the aforementioned least-squares plane by 0.122 (1) and 0.212 (1) Å, respectively. The pyran ring is bent in such a way that atom O2' of the oxaindane moiety is closer to the plane of the pyran ring. This conformation favours the conjugation between the lone pair of atom O2' and the antibonding σ-orbital of the C2—O1 bond in the pyran ring, analogous to the situation found in benzoxazinone (Bulanov et al., 2008) and other series (Minkin, 2004) of spiropyrans. The characteristics of the rather strong intramolecular hydrogen bond formed between neighbouring 7-OH and 8-formyl groups are given in Table 2.

It is interesting to compare the structural parameters of (I) with those of other previously studied representatives of the 2-oxaindane series, to evaluate the influence of incorporated chelatophore groups on the properties of the spirocentre. In the Cambridge Structural Database (version 5.30 + September 2009 updates; Allen, 2002), the crystal structures of five spiropyrans of this series determined by single-crystal X-ray diffraction are reported. A comparison of some geometric parameters is presented in Table 3. Of special interest in the spiropyran molecules is the length of the C_spiro—O bond in the pyran ring [C2—O1 in (I)], which is strongly correlated with the possibility of the opening–closing of the pyran ring reaction under internal influence. The longer this bond is, the weaker it is, and thus, at least, thermoactivation of the bond is easier. It can be seen that in (I) this bond is 1.4558 (10) Å long and it is the second longest bond in this series; it is even longer than in the case of 6-NO₂ substituent, indicating that the effect of the π-acceptor 8-formyl and π-donor 7-OH groups is synergetic and leads to activation of the C_spiro—O bond. This is promising result if we have in mind further synthesis of the ligands and their metal complexes. Thus it can be proposed that functionalization of the mother spiropyran of the oxaindane family with chelatofore groups will not influence its photochromic properties. From the data in Table 3 it is also seen that loosening of the active bond correlates rather well with shortening of the C8A—O1 and C2—O2' bonds.

In the crystal structure of (I), the formation of centrosymmetric dimers due to rather strong π-π and C—H···O interactions (see Fig. 2 and Table 2) is observed. The stacking interaction is implemented through the π systems of the aromatic rings of the 2H-chromene moieties of two molecules that are arranged strictly parallel to each other at a distance of 3.3002 (4) Å in such a way that the C atom of the formyl substituent of one molecule (C9) is close to atom C5ⁱ of the counterpart molecule [3.3843 (13) Å] and atom C7 is close to C8Aⁱ [3.2964 (12) Å] and vice versa [symmetry code: (i) -x + 1, -y + 1, -z + 1]. The distance between the centroids of the rings is 3.6095 (5) Å, which corresponds to a 1.462 Å relative shift of the molecules along the C8—C9 bond. Atoms C7—C5—C8A—C9 of both molecules form a polyhedron, which is very close to a right-angle prism. An additional cooperative effect in the stabilization of the dimers is achieved via hydrogen bonding of the C4'—H4' bond of one molecule with the hydroxy O atom of another molecule. The interatomic C4'—H4' ··· O2ⁱ distance is 2.46 Å, indicating rather strong interaction (see Table 2).

Dimers are interconnected by a weaker π–π stacking interaction between the aromatic ring of the benzopyran moiety and the aromatic ring of the oxaindane fragment in the symmetry-related molecule at (x, 3/2 - y, 1/2 + z). The angle between the planes of the aromatic rings is 9.61 (4)°, the distance between the ring centroids is 3.6804 (5) Å, the perpendicular distance of the benzopyran aromatic ring from the oxaindane aromatic ring is 3.2746 (4) Å, and the perpendicular distance of the oxaindane aromatic ring from benzopyran aromatic ring is 3.4581 (4) Å.

Related literature

For related literature, see: Fabrycy (1960).

S2. Experimental

The synthesis of (I) was performed in three successive steps. First, 1-oxy-1,3,3-trimethylphthalane, (II), was synthesized by the method described by Fabrycy (1960). Condensation of (II) with 2,4-dihydroxyisophthalic aldehyde was performed in a 1:1 (v/v) mixture of acetic acid and acetic anhydride in the presence of HClO₄ (yield 23%). The obtained 1-(2-oxystyril)-3,3-dimethyloxynaphthylisobezofurylium perchlorate was dissolved in hexane and treated with gaseous NH₃ to give a yellow solution of (I). After hexane evaporation a yellow solid was obtained and recrystallized from ethanol (m.p. 379 K). Crystals for X-ray diffraction were obtained by slow evaporation of the benzene solution.

S3. Refinement

The H atom of the hydroxy group was located in a difference Fourier synthesis. All H atoms were refined in the isotropic approximation using an appropriate riding model, with the U_iso(H) parameters constrained to 1.5U_eq(C,O) for methyl and hydroxy groups and equal to 1.2U_eq(C) for the aromatic atoms.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXTL (Version 6.12; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.12; Sheldrick, 2008); molecular graphics: Mercury (Version 2.2; Macrae et al., 2006) and SHELXTL (Version 6.12; Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Version 6.12; Sheldrick, 2008) and PLATON (Version of 25/08/09; Spek, 2009).

Figures

	Fig. 1. The crystal structure of (I) and the atom-numbering scheme used in the discussion. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres.
	Fig. 2. Close contacts in dimers of (I). [Symmetry code: (i) -x + 1, -y + 1, -z + 1.]

8-formyl-7-hydroxy-3',3'-dimethylspiro[2H-chromene-2,1'(3'H)-2- benzofuran]

Crystal data

C19H16O4	F(000) = 648
Mr = 308.32	Dx = 1.340 Mg m^−3
Monoclinic, P21/c	Melting point: 106 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 9.1470 (4) Å	Cell parameters from 7542 reflections
b = 11.1289 (4) Å	θ = 2.3–30.6°
c = 15.2605 (6) Å	µ = 0.09 mm^−1
β = 100.231 (1)°	T = 100 K
V = 1528.76 (11) Å^3	Prism, orange
Z = 4	0.24 × 0.21 × 0.18 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	4637 independent reflections
Radiation source: sealed tube	3978 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
ϕ and ω scans	θmax = 30.6°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −13→13
Tmin = 0.979, Tmax = 0.985	k = −15→15
20124 measured reflections	l = −21→21

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)] = 0.038	Hydrogen site location: mixed
wR(F^2) = 0.105	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.060P)^2 + 0.4P] where P = (Fo^2 + 2Fc^2)/3
4637 reflections	(Δ/σ)max = 0.001
210 parameters	Δρmax = 0.42 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Special details

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
O1	0.29506 (7)	0.67491 (6)	0.39494 (4)	0.01564 (13)
C2	0.30452 (10)	0.78252 (8)	0.34200 (6)	0.01467 (16)
C3	0.45448 (10)	0.84080 (8)	0.36264 (6)	0.01891 (18)
H3	0.4820	0.8966	0.3214	0.023*
C4	0.55056 (10)	0.81673 (8)	0.43720 (6)	0.01845 (18)
H4	0.6427	0.8581	0.4495	0.022*
C4A	0.51476 (9)	0.72757 (8)	0.49953 (6)	0.01491 (16)
C5	0.60401 (10)	0.70353 (9)	0.58233 (6)	0.01738 (17)
H5	0.6922	0.7490	0.6000	0.021*
C6	0.56789 (10)	0.61585 (9)	0.63901 (6)	0.01764 (17)
H6	0.6314	0.6003	0.6942	0.021*
C7	0.43685 (9)	0.55034 (8)	0.61410 (5)	0.01464 (16)
O2	0.40183 (8)	0.46621 (6)	0.67054 (4)	0.01938 (14)
H2	0.3165	0.4332	0.6406	0.029*
C8	0.34259 (9)	0.57267 (7)	0.53200 (5)	0.01293 (15)
C8A	0.38456 (9)	0.66123 (8)	0.47532 (5)	0.01298 (15)
C9	0.20309 (10)	0.50849 (8)	0.50816 (6)	0.01537 (16)
H9	0.1389	0.5300	0.4545	0.018*
O3	0.16328 (8)	0.42733 (6)	0.55393 (4)	0.01948 (14)
C1'	0.06832 (10)	0.87222 (8)	0.28845 (6)	0.01705 (17)
O2'	0.19743 (8)	0.86680 (6)	0.36012 (4)	0.01831 (14)
C3A	0.25200 (9)	0.74563 (8)	0.24677 (5)	0.01375 (16)
C4'	0.31961 (10)	0.66962 (8)	0.19361 (6)	0.01676 (17)
H4'	0.4126	0.6329	0.2158	0.020*
C5'	0.24665 (11)	0.64897 (8)	0.10669 (6)	0.01877 (18)
H5'	0.2896	0.5965	0.0692	0.023*
C6'	0.11109 (11)	0.70470 (9)	0.07426 (6)	0.01982 (18)
H6'	0.0637	0.6910	0.0145	0.024*
C7'	0.04441 (10)	0.78016 (8)	0.12846 (6)	0.01835 (18)
H7'	−0.0479	0.8179	0.1064	0.022*
C7A	0.11623 (10)	0.79892 (8)	0.21565 (6)	0.01501 (16)
C8'	−0.06516 (11)	0.81707 (10)	0.32133 (7)	0.0230 (2)
H8A	−0.0389	0.7368	0.3456	0.035*
H8B	−0.1488	0.8108	0.2716	0.035*
H8C	−0.0933	0.8682	0.3679	0.035*
C9'	0.04227 (14)	1.00371 (9)	0.26369 (7)	0.0277 (2)
H9A	0.1299	1.0362	0.2432	0.042*
H9C	0.0245	1.0489	0.3159	0.042*
H9B	−0.0444	1.0109	0.2160	0.042*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0156 (3)	0.0172 (3)	0.0128 (3)	−0.0027 (2)	−0.0011 (2)	0.0037 (2)
C2	0.0155 (4)	0.0149 (4)	0.0136 (4)	−0.0007 (3)	0.0024 (3)	0.0017 (3)
C3	0.0188 (4)	0.0192 (4)	0.0189 (4)	−0.0047 (3)	0.0038 (3)	0.0021 (3)
C4	0.0151 (4)	0.0207 (4)	0.0196 (4)	−0.0054 (3)	0.0032 (3)	−0.0003 (3)
C4A	0.0115 (3)	0.0174 (4)	0.0156 (4)	−0.0001 (3)	0.0019 (3)	−0.0009 (3)
C5	0.0118 (4)	0.0228 (4)	0.0169 (4)	−0.0003 (3)	0.0007 (3)	−0.0022 (3)
C6	0.0137 (4)	0.0239 (4)	0.0141 (4)	0.0020 (3)	−0.0008 (3)	−0.0006 (3)
C7	0.0146 (4)	0.0171 (4)	0.0122 (3)	0.0033 (3)	0.0024 (3)	0.0001 (3)
O2	0.0200 (3)	0.0224 (3)	0.0151 (3)	0.0009 (2)	0.0015 (2)	0.0047 (2)
C8	0.0117 (3)	0.0150 (4)	0.0119 (3)	0.0015 (3)	0.0015 (3)	−0.0003 (3)
C8A	0.0113 (3)	0.0154 (4)	0.0120 (3)	0.0015 (3)	0.0015 (3)	−0.0006 (3)
C9	0.0144 (4)	0.0167 (4)	0.0148 (4)	−0.0004 (3)	0.0021 (3)	0.0000 (3)
O3	0.0198 (3)	0.0197 (3)	0.0193 (3)	−0.0032 (2)	0.0044 (2)	0.0027 (2)
C1'	0.0186 (4)	0.0170 (4)	0.0162 (4)	0.0047 (3)	0.0048 (3)	0.0033 (3)
O2'	0.0190 (3)	0.0185 (3)	0.0173 (3)	0.0027 (2)	0.0031 (2)	−0.0026 (2)
C3A	0.0145 (4)	0.0136 (3)	0.0130 (4)	0.0002 (3)	0.0021 (3)	0.0021 (3)
C4'	0.0183 (4)	0.0146 (4)	0.0182 (4)	0.0021 (3)	0.0055 (3)	0.0023 (3)
C5'	0.0251 (4)	0.0164 (4)	0.0165 (4)	−0.0023 (3)	0.0082 (3)	−0.0003 (3)
C6'	0.0234 (4)	0.0224 (4)	0.0132 (4)	−0.0058 (3)	0.0021 (3)	0.0026 (3)
C7'	0.0164 (4)	0.0213 (4)	0.0167 (4)	−0.0002 (3)	0.0010 (3)	0.0063 (3)
C7A	0.0156 (4)	0.0146 (4)	0.0152 (4)	0.0019 (3)	0.0037 (3)	0.0041 (3)
C8'	0.0177 (4)	0.0317 (5)	0.0208 (4)	0.0023 (4)	0.0062 (3)	0.0039 (4)
C9'	0.0403 (6)	0.0184 (4)	0.0277 (5)	0.0116 (4)	0.0149 (4)	0.0065 (4)

Geometric parameters (Å, º)

O1—C2	1.4558 (10)	C9—O3	1.2356 (11)
O1—C8A	1.3570 (10)	C9—H9	0.9500
C2—O2'	1.4185 (11)	C1'—C7A	1.5049 (12)
C1'—O2'	1.4614 (11)	C1'—C9'	1.5196 (13)
C2—C3	1.4993 (12)	C1'—C8'	1.5286 (13)
C2—C3A	1.5044 (12)	C3A—C7A	1.3820 (12)
C3—C4	1.3355 (13)	C3A—C4'	1.3908 (12)
C3—H3	0.9500	C4'—C5'	1.3941 (13)
C4—C4A	1.4517 (12)	C4'—H4'	0.9500
C4—H4	0.9500	C5'—C6'	1.3961 (14)
C4A—C8A	1.3941 (12)	C5'—H5'	0.9500
C4A—C5	1.4029 (12)	C6'—C7'	1.3931 (13)
C5—C6	1.3824 (13)	C6'—H6'	0.9500
C5—H5	0.9500	C7'—C7A	1.3911 (12)
C6—C7	1.3968 (13)	C7'—H7'	0.9500
C6—H6	0.9500	C8'—H8A	0.9800
C7—O2	1.3487 (11)	C8'—H8B	0.9800
C7—C8	1.4111 (11)	C8'—H8C	0.9800
O2—H2	0.9090	C9'—H9A	0.9800
C8—C8A	1.4088 (12)	C9'—H9C	0.9800
C8—C9	1.4512 (12)	C9'—H9B	0.9800
O1—C2—C3	112.44 (7)	O2'—C1'—C7A	103.16 (7)
O2'—C2—C3A	104.81 (7)	O2'—C1'—C9'	107.22 (8)
C8A—O1—C2	120.54 (7)	C7A—C1'—C9'	113.06 (8)
C2—O2'—C1'	112.06 (7)	O2'—C1'—C8'	108.91 (7)
O2'—C2—O1	108.94 (7)	C7A—C1'—C8'	112.27 (8)
O2'—C2—C3	108.11 (7)	C9'—C1'—C8'	111.67 (8)
O1—C2—C3A	105.74 (7)	C7A—C3A—C4'	121.74 (8)
C3—C2—C3A	116.37 (7)	C7A—C3A—C2	109.16 (7)
C4—C3—C2	122.09 (8)	C4'—C3A—C2	129.09 (8)
C4—C3—H3	119.0	C3A—C4'—C5'	117.90 (8)
C2—C3—H3	119.0	C3A—C4'—H4'	121.0
C3—C4—C4A	120.30 (8)	C5'—C4'—H4'	121.0
C3—C4—H4	119.9	C4'—C5'—C6'	120.60 (9)
C4A—C4—H4	119.9	C4'—C5'—H5'	119.7
C8A—C4A—C5	118.09 (8)	C6'—C5'—H5'	119.7
C8A—C4A—C4	118.02 (8)	C7'—C6'—C5'	120.81 (8)
C5—C4A—C4	123.89 (8)	C7'—C6'—H6'	119.6
C6—C5—C4A	122.18 (8)	C5'—C6'—H6'	119.6
C6—C5—H5	118.9	C7A—C7'—C6'	118.44 (8)
C4A—C5—H5	118.9	C7A—C7'—H7'	120.8
C5—C6—C7	119.15 (8)	C6'—C7'—H7'	120.8
C5—C6—H6	120.4	C3A—C7A—C7'	120.48 (8)
C7—C6—H6	120.4	C3A—C7A—C1'	109.91 (8)
O2—C7—C6	118.57 (8)	C7'—C7A—C1'	129.61 (8)
O2—C7—C8	120.82 (8)	C1'—C8'—H8A	109.5
C6—C7—C8	120.61 (8)	C1'—C8'—H8B	109.5
C8A—C8—C7	118.57 (8)	H8A—C8'—H8B	109.5
C8A—C8—C9	120.92 (7)	C1'—C8'—H8C	109.5
C7—C8—C9	120.48 (8)	H8A—C8'—H8C	109.5
O1—C8A—C4A	122.00 (8)	H8B—C8'—H8C	109.5
O1—C8A—C8	116.56 (7)	C1'—C9'—H9A	109.5
C4A—C8A—C8	121.39 (8)	C1'—C9'—H9C	109.5
O3—C9—C8	123.54 (8)	H9A—C9'—H9C	109.5
O3—C9—H9	118.2	C1'—C9'—H9B	109.5
C7—O2—H2	103.9	H9A—C9'—H9B	109.5
C8—C9—H9	118.2	H9C—C9'—H9B	109.5
C8A—O1—C2—O2'	−94.20 (9)	O1—C2—O2'—C1'	−103.69 (8)
C8A—O1—C2—C3	25.62 (11)	C3—C2—O2'—C1'	133.84 (7)
C8A—O1—C2—C3A	153.62 (7)	C3A—C2—O2'—C1'	9.10 (9)
O2'—C2—C3—C4	102.49 (10)	C7A—C1'—O2'—C2	−9.69 (9)
O1—C2—C3—C4	−17.81 (13)	C9'—C1'—O2'—C2	−129.27 (8)
C3A—C2—C3—C4	−139.97 (9)	C8'—C1'—O2'—C2	109.75 (8)
C2—C3—C4—C4A	3.00 (14)	O2'—C2—C3A—C7A	−4.69 (9)
C3—C4—C4A—C8A	5.64 (13)	O1—C2—C3A—C7A	110.36 (8)
C3—C4—C4A—C5	−174.91 (9)	C3—C2—C3A—C7A	−124.02 (8)
C8A—C4A—C5—C6	1.02 (13)	O2'—C2—C3A—C4'	176.25 (8)
C4—C4A—C5—C6	−178.43 (9)	O1—C2—C3A—C4'	−68.70 (11)
C4A—C5—C6—C7	−1.27 (14)	C3—C2—C3A—C4'	56.92 (12)
C5—C6—C7—O2	−179.08 (8)	C7A—C3A—C4'—C5'	0.52 (13)
C5—C6—C7—C8	0.31 (13)	C2—C3A—C4'—C5'	179.48 (8)
O2—C7—C8—C8A	−179.78 (7)	C3A—C4'—C5'—C6'	0.94 (13)
C6—C7—C8—C8A	0.83 (12)	C4'—C5'—C6'—C7'	−1.28 (14)
O2—C7—C8—C9	2.32 (12)	C5'—C6'—C7'—C7A	0.14 (13)
C6—C7—C8—C9	−177.06 (8)	C4'—C3A—C7A—C7'	−1.67 (13)
C2—O1—C8A—C4A	−19.12 (12)	C2—C3A—C7A—C7'	179.19 (8)
C2—O1—C8A—C8	163.48 (7)	C4'—C3A—C7A—C1'	177.92 (8)
C5—C4A—C8A—O1	−177.09 (8)	C2—C3A—C7A—C1'	−1.22 (10)
C4—C4A—C8A—O1	2.39 (12)	C6'—C7'—C7A—C3A	1.31 (13)
C5—C4A—C8A—C8	0.19 (12)	C6'—C7'—C7A—C1'	−178.19 (9)
C4—C4A—C8A—C8	179.67 (8)	O2'—C1'—C7A—C3A	6.42 (9)
C7—C8—C8A—O1	176.33 (7)	C9'—C1'—C7A—C3A	121.88 (9)
C9—C8—C8A—O1	−5.78 (12)	C8'—C1'—C7A—C3A	−110.67 (9)
C7—C8—C8A—C4A	−1.09 (12)	O2'—C1'—C7A—C7'	−174.03 (9)
C9—C8—C8A—C4A	176.80 (8)	C9'—C1'—C7A—C7'	−58.57 (13)
C8A—C8—C9—O3	177.49 (8)	C8'—C1'—C7A—C7'	68.87 (12)
C7—C8—C9—O3	−4.67 (13)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3	0.91	1.75	2.5953 (10)	154
C4′—H4′···O2^i	0.95	2.46	3.3465 (11)	155

Symmetry code: (i) −x+1, −y+1, −z+1.