Methyl 7-meth­oxy-9-oxo-9H-xanthene-2-carboxyl­ate

Niedziałkowski, P.; Ossowski, T.; Sikorski, A.

doi:10.1107/S1600536809003602

organic compounds

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ISSN: 2056-9890

Volume 65| Part 3| March 2009| Pages o484-o485

doi:10.1107/S1600536809003602

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Methyl 7-methoxy-9-oxo-9H-xanthene-2-carboxylate

Paweł Niedziałkowski,^a Tadeusz Ossowski ^a and Artur Sikorski ^a ^*

^aUniversity of Gdańsk, Faculty of Chemistry, Sobieskiego 18/19, 80-952 Gdańsk, Poland
^*Correspondence e-mail: art@chem.univ.gda.pl

(Received 25 January 2009; accepted 29 January 2009; online 6 February 2009)

The crystal structure of the title compound, C₁₆H₁₂O₅, is stabilized by C—H⋯O hydrogen bonds and C=O⋯π interactions; π–π interactions are also present. With respective average deviations from planarity of 0.003 (2) and 0.002 (1) Å, the xanthone and ester fragments are oriented at an angle of 2.8 (2)° with respect to each other. The mean planes of the xanthone skeleton lie either parallel to each other or are inclined at an angle of 85.5 (2)° in the crystal structure.

Related literature

For general background and uses of xanthones, see: Chen et al. (1993 ); Denisova-Dyatlova & Glyzin (1982 ); Fukai et al. (2005 ); Gopalakrishnan et al. (1997 ); Ignatushchenko et al. (2000 ); Ito et al. (2003 ); Librowski et al. (2005 ); Pfister et al. (1972 , 1980 ). For related structures, see: Evans et al. (2004 ); Shi et al. (2004 ); Macias et al. (2001 ). For synthesis, see: Geertsema et al. (2006 ). For background to the various types of intermolecular interactions, see: Bianchi et al. (2004 ); Steiner (1999 ) Santos-Contreras et al. (2007 ); Hunter & Sanders (1990 ). For analysis of intermolecular interactions, see: Spek (2003 ).

Experimental

Crystal data

C₁₆H₁₂O₅
M_r = 284.26
Monoclinic, P 2₁ /c
a = 4.7709 (4) Å
b = 10.5375 (8) Å
c = 26.7854 (19) Å
β = 93.266 (7)°
V = 1344.40 (18) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 295 (2) K
0.20 × 0.04 × 0.04 mm

Data collection

Oxford Diffraction Ruby CCD diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]$ ) T_min = 0.994, T_max = 0.997
23842 measured reflections
2366 independent reflections
1051 reflections with I > 2σ(I)
R_int = 0.086

Refinement

R[F² > 2σ(F²)] = 0.038
wR(F²) = 0.092
S = 0.81
2366 reflections
193 parameters
H-atom parameters constrained
Δρ_max = 0.13 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯O16ⁱ	0.93	2.54	3.362 (3)	147
C20—H20A⋯O21ⁱⁱ	0.96	2.50	3.454 (3)	173
Symmetry codes: (i) -x+2, -y+1, -z+1; (ii) $[-x-1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Table 2
π–π interactions (Å,°)

CgI	CgJ	Cg⋯Cg	Dihedral angle	Interplanar distance	Offset
A	Cⁱⁱⁱ	3.549 (1)	0.8	3.420 (1)	1.068 (1)
B	Aⁱⁱⁱ	3.583 (1)	0.1	3.454 (1)	0.953 (1)
B	Cⁱⁱⁱ	3.772 (1)	0.8	3.455 (1)	1.525 (1)
Symmetry code: (iii) 1 + x, y, z. CgA, CgB and CgC are the centroids of the C9/O10/C11–C14, C1–C4/C12/C11 and C5–C8/C13/C14 rings, respectively. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J.

Table 3
C—O⋯π interactions (Å,°)

X	I	J	I⋯J	X⋯J	X—I⋯J
C15	O16	CgBⁱⁱⁱ	3.564 (2)	3.689 (2)	86.4 (1)
Symmetry code: (iii) 1 + x, y, z. CgB is the centroid of the C1–C4/C12/C11 ring.

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]$ ); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 $[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]$ ); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976 ); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809003602/xu2476sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809003602/xu2476Isup2.hkl

checkCIF report

Comment top

Xanthones represent a structurally diverse group of natural products with a broad range of biological activities. The unsubstituted xanthones have not been discovered in nature but its numerous derivatives have been isolated from representatives of higher plants, lichens, and lower fungi (Denisova-Dyatlova & Glyzin, 1982). Many naturally occurring xanthones as well as their synthetic derivatives described in numerous scientific publications exploit wide spectrum of biological activities: anti-allergic (Pfister et al., 1972), anti-inflammatory (Librowski et al., 2005), antitumor (Ito et al., 2003), antimicrobial (Fukai et al., 2005), cardiovascular (Chen et al., 1993), antimalarial (Gopalakrishnan et al., 1997) and antifungal activity (Ignatushchenko et al., 2000). The biological activity and the features responsible for the activity of xanthones largely depends on their structures. It is know that the 7-substituted xanthone-2-carboxylic acids and their esters show anti-allergic activity, which depends on the substituted groups (Pfister et al., 1980).

In the molecule of the title compound (Fig. 1) the bond lengths and angles characterizing the geometry of the xanthone skeleton are typical for this group compounds (Evans et al., 2004; Shi et al., 2004; Macias et al., 2001).

With respective average deviations from planarity of 0.003 (2) and 0.002 (1) Å, the xanthone and ester fragment are oriented at 2.8 (2)° to each other. The methoxy group lies nearly in the mean plane of the xanthone skeleton; the dihedral angles between the mean planes xanthone skeleton and delineated by atoms C7/O19/C20 are equal 0.7 (2)°. The mean planes of the xanthone skeleton lie either parallel or are inclined at an angle of 85.5 (2)° in the lattice.

In the crystal structure, weak intermolecular C—H···O hydrogen bonds (Table 1, Fig. 2) link the molecules, forming layers. The central ring A and the lateral rings B and C are involved in multidirectional π–π interactions and link layers between themselves (Table 2, Fig. 3). The O16(carboxyl) atom is involved in weak C—O···π interactions directed toward the lateral aromatic ring (ring B) (Table 3, Fig. 3).

All the interactions demonstrated were found by PLATON (Spek, 2003). The C—H···O (Bianchi et al., 2004; Steiner, 1999) interactions exhibit a hydrogen-bond-type nature. The C—O(carbonyl)···π interactions (Santos-Contreras et al., 2007), and also π–π interactions (Hunter & Sanders, 1990) should be of an attractive nature.

Related literature top

For general background and uses of xanthones, see: Chen et al. (1993); Denisova-Dyatlova & Glyzin (1982); Fukai et al. (2005); Gopalakrishnan et al. (1997); Ignatushchenko et al. (2000); Ito et al. (2003); Librowski et al. (2005); Pfister et al. (1972, 1980). For related structures, see: Evans et al. (2004); Shi et al. (2004); Macias et al. (2001). For synthesis, see: Geertsema et al. (2006). For background to the various types of intermolecular interactions, see: Bianchi et al. (2004); Steiner (1999) Santos-Contreras et al. (2007); Hunter & Sanders (1990). For analysis of intermolecular interactions, see: Spek (2003). [Please check rephrasing]

Experimental top

7-Methoxy-9-oxo-9H-xanthene-2-carboxylatic acid methyl ester was synthesized by three steps. First, in a nucleophilic substitution of 4-methoxyphenol and 4-bromoisophthalic acid, to yield 4-(4-methoxyphenoxy)isophthalic acid, by refluxing 45 min in N,N-dimethylformamide with potassium carbonate, sodium iodide and activated Cu-bronze. In the next reaction, called intramolecular Friedel–Crafts acylation was synthesized 7-methoxy-9-oxo-9H-xanthene-2-carboxylatic acid (Geertsema et al., 2006). In last step 7-methoxy-9-oxo-9H-xanthene-2-carboxylatic acid was esterified with methanol by refluxing in thionyl chloride in 45 min and then treated with mixture of methanol and triethylamine in room temperature by 12 h with catalytic amount of 4-dimethylaminopyridine (DMAP). The crude product was dissolved in small amount of anhydrous methanol to obtain single crystals suitable for X-ray analysis by slow evaporation of methanol solution at 298 K.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures top

	Fig. 1. The molecular structure of the title compound showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 25% probability level and H atoms are shown as small spheres of arbitrary radius. CgA, CgB and CgC denote the ring centroids.
	Fig. 2. The arrangement of the molecules in the crystal structure viewed approximately along a axis. The C—H···O interactions are represented by dashed lines. H atoms not involved in the interactions have been omitted. [Symmetry codes: (i) 2 - x, 1 - y, 1 - z; (ii) -1 - x, -1/2 + y, 1/2 - z.]
	Fig. 3. The arrangement of the molecules in the crystal structure viewed approximately along a axis. The C—H···O and C—O···π interactions are represented by dashed lines and the π–π interactions are represented by dotted lines. H atoms not involved in the interactions have been omitted. [Symmetry codes: (iii) 1 + x, y, z.]

Methyl 7-methoxy-9-oxo-9H-xanthene-2-carboxylate top

Crystal data top

C₁₆H₁₂O₅	F(000) = 592.0
M_r = 284.26	D_x = 1.404 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2126 reflections
a = 4.7709 (4) Å	θ = 3.0–25.0°
b = 10.5375 (8) Å	µ = 0.11 mm⁻¹
c = 26.7854 (19) Å	T = 295 K
β = 93.266 (7)°	Needle, white
V = 1344.40 (18) Å³	0.2 × 0.04 × 0.04 mm
Z = 4

Data collection top

Oxford Diffraction Ruby CCD diffractometer	2366 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1051 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.086
Detector resolution: 10.4002 pixels mm^-1	θ_max = 25.0°, θ_min = 3.0°
ω scans	h = −5→5
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008)	k = −12→12
T_min = 0.994, T_max = 0.997	l = −31→31
23842 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.092	H-atom parameters constrained
S = 0.81	w = 1/[σ²(F_o²) + (0.0471P)²] where P = (F_o² + 2F_c²)/3
2366 reflections	(Δ/σ)_max = 0.001
193 parameters	Δρ_max = 0.13 e Å⁻³
0 restraints	Δρ_min = −0.14 e Å⁻³

Crystal data top

C₁₆H₁₂O₅	V = 1344.40 (18) Å³
M_r = 284.26	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 4.7709 (4) Å	µ = 0.11 mm⁻¹
b = 10.5375 (8) Å	T = 295 K
c = 26.7854 (19) Å	0.2 × 0.04 × 0.04 mm
β = 93.266 (7)°

Data collection top

Oxford Diffraction Ruby CCD diffractometer	2366 independent reflections
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008)	1051 reflections with I > 2σ(I)
T_min = 0.994, T_max = 0.997	R_int = 0.086
23842 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.038	0 restraints
wR(F²) = 0.092	H-atom parameters constrained
S = 0.81	Δρ_max = 0.13 e Å⁻³
2366 reflections	Δρ_min = −0.14 e Å⁻³
193 parameters

Special details top

Experimental. CrysAlis RED, Version 1.171.32.15 (Oxford Diffraction Ltd., 2008) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

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

	x	y	z	U_iso*/U_eq
C1	0.4869 (4)	0.3741 (2)	0.37390 (8)	0.0507 (6)
H1	0.4950	0.4005	0.3409	0.061*
C2	0.6568 (4)	0.4321 (2)	0.41017 (8)	0.0531 (6)
C3	0.6434 (5)	0.3912 (2)	0.45962 (9)	0.0678 (7)
H3	0.7584	0.4289	0.4846	0.081*
C4	0.4634 (5)	0.2964 (3)	0.47187 (9)	0.0735 (7)
H4	0.4548	0.2703	0.5049	0.088*
C5	−0.2272 (5)	−0.0083 (2)	0.43087 (9)	0.0742 (7)
H5	−0.2221	−0.0287	0.4647	0.089*
C6	−0.4064 (5)	−0.0705 (2)	0.39752 (9)	0.0723 (7)
H6	−0.5229	−0.1337	0.4089	0.087*
C7	−0.4169 (4)	−0.0408 (2)	0.34712 (9)	0.0570 (6)
C8	−0.2448 (4)	0.0520 (2)	0.33022 (8)	0.0506 (6)
H8	−0.2514	0.0723	0.2964	0.061*
C9	0.1240 (4)	0.2157 (2)	0.34601 (8)	0.0485 (5)
O10	0.1221 (3)	0.14529 (15)	0.44927 (5)	0.0685 (5)
C11	0.3026 (4)	0.2770 (2)	0.38514 (7)	0.0469 (5)
C12	0.2945 (4)	0.2399 (2)	0.43445 (8)	0.0567 (6)
C13	−0.0592 (4)	0.1163 (2)	0.36375 (7)	0.0459 (5)
C14	−0.0538 (4)	0.0853 (2)	0.41369 (8)	0.0567 (6)
C15	0.8493 (5)	0.5368 (2)	0.39863 (10)	0.0616 (6)
O16	0.9949 (4)	0.59309 (17)	0.42912 (7)	0.0897 (6)
O17	0.8478 (3)	0.56064 (15)	0.34987 (6)	0.0748 (5)
C18	1.0307 (5)	0.6610 (2)	0.33454 (10)	0.0877 (8)
H18A	0.9931	0.6783	0.2996	0.132*
H18B	1.2228	0.6352	0.3403	0.132*
H18C	0.9978	0.7362	0.3536	0.132*
O19	−0.6050 (3)	−0.10926 (15)	0.31785 (6)	0.0734 (5)
C20	−0.6235 (5)	−0.0814 (3)	0.26581 (9)	0.0837 (8)
H20A	−0.7623	−0.1351	0.2493	0.126*
H20B	−0.4446	−0.0962	0.2522	0.126*
H20C	−0.6760	0.0058	0.2609	0.126*
O21	0.1291 (3)	0.24526 (14)	0.30176 (5)	0.0657 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0541 (13)	0.0547 (16)	0.0427 (13)	0.0009 (12)	−0.0024 (11)	−0.0013 (11)
C2	0.0517 (13)	0.0553 (16)	0.0518 (15)	−0.0049 (11)	−0.0025 (11)	−0.0058 (12)
C3	0.0741 (15)	0.0794 (19)	0.0481 (16)	−0.0117 (14)	−0.0139 (11)	−0.0116 (14)
C4	0.0851 (17)	0.087 (2)	0.0471 (14)	−0.0246 (16)	−0.0071 (13)	0.0017 (14)
C5	0.0855 (16)	0.084 (2)	0.0519 (15)	−0.0292 (15)	−0.0047 (13)	0.0166 (14)
C6	0.0777 (16)	0.0703 (19)	0.0681 (19)	−0.0229 (14)	−0.0016 (14)	0.0133 (15)
C7	0.0565 (13)	0.0599 (16)	0.0535 (15)	−0.0049 (13)	−0.0053 (11)	0.0004 (13)
C8	0.0532 (12)	0.0517 (15)	0.0464 (13)	−0.0031 (11)	−0.0022 (11)	−0.0001 (11)
C9	0.0491 (13)	0.0508 (15)	0.0449 (14)	0.0006 (11)	−0.0036 (11)	0.0031 (12)
O10	0.0800 (10)	0.0808 (13)	0.0429 (9)	−0.0254 (9)	−0.0104 (8)	0.0102 (8)
C11	0.0475 (12)	0.0498 (15)	0.0427 (13)	−0.0023 (11)	−0.0027 (10)	0.0012 (11)
C12	0.0584 (13)	0.0629 (17)	0.0476 (14)	−0.0139 (13)	−0.0063 (11)	0.0007 (12)
C13	0.0470 (12)	0.0466 (14)	0.0436 (14)	0.0005 (11)	−0.0022 (10)	0.0020 (11)
C14	0.0617 (14)	0.0596 (17)	0.0473 (15)	−0.0124 (12)	−0.0087 (11)	0.0037 (12)
C15	0.0620 (15)	0.0620 (18)	0.0598 (17)	−0.0037 (13)	−0.0044 (12)	−0.0063 (15)
O16	0.1020 (13)	0.0906 (14)	0.0742 (12)	−0.0367 (11)	−0.0143 (10)	−0.0106 (11)
O17	0.0865 (11)	0.0729 (13)	0.0641 (12)	−0.0294 (10)	−0.0039 (9)	0.0052 (9)
C18	0.0935 (18)	0.078 (2)	0.092 (2)	−0.0274 (16)	0.0074 (15)	0.0129 (16)
O19	0.0772 (10)	0.0744 (12)	0.0671 (12)	−0.0265 (9)	−0.0081 (8)	−0.0049 (9)
C20	0.0931 (18)	0.102 (2)	0.0549 (17)	−0.0282 (16)	−0.0058 (13)	−0.0135 (15)
O21	0.0744 (10)	0.0781 (12)	0.0432 (9)	−0.0200 (8)	−0.0084 (7)	0.0105 (8)

Geometric parameters (Å, º) top

C1—C2	1.373 (3)	C9—O21	1.227 (2)
C1—C11	1.394 (3)	C9—C13	1.461 (3)
C1—H1	0.9300	C9—C11	1.462 (3)
C2—C3	1.398 (3)	O10—C12	1.366 (2)
C2—C15	1.480 (3)	O10—C14	1.386 (2)
C3—C4	1.369 (3)	C11—C12	1.380 (3)
C3—H3	0.9300	C13—C14	1.376 (3)
C4—C12	1.384 (3)	C15—O16	1.199 (2)
C4—H4	0.9300	C15—O17	1.330 (3)
C5—C6	1.368 (3)	O17—C18	1.446 (3)
C5—C14	1.383 (3)	C18—H18A	0.9600
C5—H5	0.9300	C18—H18B	0.9600
C6—C7	1.384 (3)	C18—H18C	0.9600
C6—H6	0.9300	O19—C20	1.422 (3)
C7—O19	1.364 (2)	C20—H20A	0.9600
C7—C8	1.370 (3)	C20—H20B	0.9600
C8—C13	1.400 (3)	C20—H20C	0.9600
C8—H8	0.9300

C2—C1—C11	121.9 (2)	C12—C11—C9	120.9 (2)
C2—C1—H1	119.1	C1—C11—C9	121.22 (19)
C11—C1—H1	119.1	O10—C12—C11	122.33 (19)
C1—C2—C3	118.4 (2)	O10—C12—C4	116.0 (2)
C1—C2—C15	122.2 (2)	C11—C12—C4	121.6 (2)
C3—C2—C15	119.4 (2)	C14—C13—C8	119.0 (2)
C4—C3—C2	121.0 (2)	C14—C13—C9	120.5 (2)
C4—C3—H3	119.5	C8—C13—C9	120.44 (19)
C2—C3—H3	119.5	C13—C14—C5	121.0 (2)
C3—C4—C12	119.2 (2)	C13—C14—O10	122.5 (2)
C3—C4—H4	120.4	C5—C14—O10	116.5 (2)
C12—C4—H4	120.4	O16—C15—O17	123.1 (2)
C6—C5—C14	119.2 (2)	O16—C15—C2	124.7 (2)
C6—C5—H5	120.4	O17—C15—C2	112.2 (2)
C14—C5—H5	120.4	C15—O17—C18	116.59 (19)
C5—C6—C7	121.0 (2)	O17—C18—H18A	109.5
C5—C6—H6	119.5	O17—C18—H18B	109.5
C7—C6—H6	119.5	H18A—C18—H18B	109.5
O19—C7—C8	125.1 (2)	O17—C18—H18C	109.5
O19—C7—C6	115.3 (2)	H18A—C18—H18C	109.5
C8—C7—C6	119.6 (2)	H18B—C18—H18C	109.5
C7—C8—C13	120.2 (2)	C7—O19—C20	117.16 (17)
C7—C8—H8	119.9	O19—C20—H20A	109.5
C13—C8—H8	119.9	O19—C20—H20B	109.5
O21—C9—C13	122.78 (19)	H20A—C20—H20B	109.5
O21—C9—C11	122.5 (2)	O19—C20—H20C	109.5
C13—C9—C11	114.73 (19)	H20A—C20—H20C	109.5
C12—O10—C14	118.97 (16)	H20B—C20—H20C	109.5
C12—C11—C1	117.8 (2)

C11—C1—C2—C3	0.3 (3)	C3—C4—C12—C11	−0.1 (4)
C11—C1—C2—C15	−178.91 (19)	C7—C8—C13—C14	−0.3 (3)
C1—C2—C3—C4	−0.6 (3)	C7—C8—C13—C9	−179.76 (19)
C15—C2—C3—C4	178.6 (2)	O21—C9—C13—C14	178.94 (19)
C2—C3—C4—C12	0.6 (4)	C11—C9—C13—C14	−0.7 (3)
C14—C5—C6—C7	−0.2 (4)	O21—C9—C13—C8	−1.6 (3)
C5—C6—C7—O19	−179.7 (2)	C11—C9—C13—C8	178.67 (18)
C5—C6—C7—C8	0.2 (4)	C8—C13—C14—C5	0.3 (3)
O19—C7—C8—C13	−179.99 (19)	C9—C13—C14—C5	179.7 (2)
C6—C7—C8—C13	0.1 (3)	C8—C13—C14—O10	−179.42 (18)
C2—C1—C11—C12	0.1 (3)	C9—C13—C14—O10	0.0 (3)
C2—C1—C11—C9	−179.66 (19)	C6—C5—C14—C13	−0.1 (4)
O21—C9—C11—C12	−179.0 (2)	C6—C5—C14—O10	179.7 (2)
C13—C9—C11—C12	0.7 (3)	C12—O10—C14—C13	0.8 (3)
O21—C9—C11—C1	0.8 (3)	C12—O10—C14—C5	−178.9 (2)
C13—C9—C11—C1	−179.53 (17)	C1—C2—C15—O16	177.5 (2)
C14—O10—C12—C11	−0.8 (3)	C3—C2—C15—O16	−1.7 (4)
C14—O10—C12—C4	179.6 (2)	C1—C2—C15—O17	−3.8 (3)
C1—C11—C12—O10	−179.70 (17)	C3—C2—C15—O17	177.05 (19)
C9—C11—C12—O10	0.1 (3)	O16—C15—O17—C18	−0.8 (3)
C1—C11—C12—C4	−0.2 (3)	C2—C15—O17—C18	−179.59 (18)
C9—C11—C12—C4	179.6 (2)	C8—C7—O19—C20	−0.2 (3)
C3—C4—C12—O10	179.4 (2)	C6—C7—O19—C20	179.7 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O16ⁱ	0.93	2.54	3.362 (3)	147
C20—H20A···O21ⁱⁱ	0.96	2.50	3.454 (3)	173

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x−1, y−1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₂O₅
M_r	284.26
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	295
a, b, c (Å)	4.7709 (4), 10.5375 (8), 26.7854 (19)
β (°)	93.266 (7)
V (Å³)	1344.40 (18)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.11
Crystal size (mm)	0.2 × 0.04 × 0.04

Data collection
Diffractometer	Oxford Diffraction Ruby CCD diffractometer
Absorption correction	Multi-scan (CrysAlis RED; Oxford Diffraction, 2008)
T_min, T_max	0.994, 0.997
No. of measured, independent and observed [I > 2σ(I)] reflections	23842, 2366, 1051
R_int	0.086
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.038, 0.092, 0.81
No. of reflections	2366
No. of parameters	193
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.13, −0.14

Computer programs: CrysAlis CCD (Oxford Diffraction, 2008), CrysAlis RED (Oxford Diffraction, 2008), SHELXS97 (Sheldrick, 2008), ORTEPII (Johnson, 1976), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2003).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O16ⁱ	0.93	2.54	3.362 (3)	147
C20—H20A···O21ⁱⁱ	0.96	2.50	3.454 (3)	173

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x−1, y−1/2, −z+1/2.

π–π interactions (Å,°). top

CgI	CgJ	Cg···Cg	Dihedral angle	Interplanar distance	Offset
A	Cⁱⁱⁱ	3.549 (1)	0.8	3.420 (1)	1.068 (1)
B	Aⁱⁱⁱ	3.583 (1)	0.1	3.454 (1)	0.953 (1)
B	Cⁱⁱⁱ	3.772 (1)	0.8	3.455 (1)	1.525 (1)

Symmetry code: (iii) 1 + x, y, z. CgA, CgB and CgC are the centroids of the C9/O10/C11–C14, C1–C4/C12/C11 and C5–C8/C13/C14 rings, respectively. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J.

C—O···π interactions (Å,°) top

X	I	J	I···J	X···J	X-I···J
C15	O16	CgBⁱⁱⁱ	3.564 (2)	3.689 (2)	86.4 (1)

Symmetry codes: (iii) 1 + x, y, z.

Notes: CgB is the centroid of the C1–C4/C12/C11 ring.

Acknowledgements

This work was supported by Funds for Science in 2008 as a Research Project (No. BW-8000-5-0453-8).

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