2-Hydroxy­platyphyllid

Wang, Q.; Chen, D.-F.

doi:10.1107/S1600536807037105

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2-Hydroxyplatyphyllid

Q. Wang and D.-F. Chen

The title compound [systematic name 4-hydroxy-3-(1-methylethylidene)-6,7,8,8a-tetrahydro-1-oxaacenaphthylen-2-one], C₁₄H₁₄O₃, is a tricyclic norsesquiterpene. The structure has a pseudo-centre of symmetry (possibility of space group Pnma). However, the unit cell contains only four molecules which have no internal symmetry. The molecules are linked into one dimensional chains along the b axis through O—H

O hydrogen bonding.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807037105/fl2135sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536807037105/fl2135Isup2.hkl Contains datablock I

CCDC reference: 663734

checkCIF report

Key indicators

Single-crystal X-ray study
T = 293 K
Mean (C-C) = 0.007 Å
R factor = 0.079
wR factor = 0.164
Data-to-parameter ratio = 9.9

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....         88 PerFi
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for        C11

Alert level C
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT150_ALERT_1_C Volume as Calculated Differs from that Given ...    1212.00 Ang-3
PLAT165_ALERT_3_C Nr. of Status R Flagged Non-Hydrogen Atoms .....          1
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.89 Ratio
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.20 Ratio
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          7
PLAT751_ALERT_4_C Bond    Calc     1.19599, Rep    1.196(4) ......  Senseless su
              O2   -C14     1.555   1.555
PLAT751_ALERT_4_C Bond    Calc     1.35655, Rep    1.356(4) ......  Senseless su
              O3   -C14     1.555   1.555
PLAT751_ALERT_4_C Bond    Calc     1.48713, Rep    1.487(5) ......  Senseless su
              C4   -C14     1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      110.08, Rep    110.1(3) ......  Senseless su
              C14  -O3   -C6      1.555   1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      105.97, Rep    106.0(4) ......  Senseless su
              C5   -C4   -C14     1.555   1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      131.53, Rep    131.5(4) ......  Senseless su
              C3   -C4   -C14     1.555   1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      121.93, Rep    121.9(3) ......  Senseless su
              O2   -C14  -O3      1.555   1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      129.43, Rep    129.5(4) ......  Senseless su
              O2   -C14  -C4      1.555   1.555   1.555
PLAT752_ALERT_4_C Angle   Calc      108.64, Rep    108.6(3) ......  Senseless su
              O3   -C14  -C4      1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc     -168.73, Rep   -168.7(5) ......  Senseless su
              C2  -C3  -C4  -C14    1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc      164.93, Rep    165.0(4) ......  Senseless su
              C14 -C4  -C5  -C10    1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc       -6.39, Rep     -6.4(5) ......  Senseless su
              C14 -C4  -C5  -C6     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc      -10.43, Rep    -10.4(4) ......  Senseless su
              C14 -O3  -C6  -C5     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc     -132.33, Rep   -132.3(4) ......  Senseless su
              C14 -O3  -C6  -C7     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc     -173.35, Rep   -173.4(5) ......  Senseless su
              C6  -O3  -C14 -O2     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc        7.05, Rep      7.0(5) ......  Senseless su
              C6  -O3  -C14 -C4     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc       -8.72, Rep    -8.7(10) ......  Senseless su
              C3  -C4  -C14 -O2     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc       -0.46, Rep     -0.5(6) ......  Senseless su
              C5  -C4  -C14 -O3     1.555   1.555   1.555   1.555
PLAT753_ALERT_4_C Torsion Calc      170.83, Rep    170.9(5) ......  Senseless su
              C3  -C4  -C14 -O3     1.555   1.555   1.555   1.555

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.10
           From the CIF: _reflns_number_total               1549
           Count of symmetry unique reflns         1558
           Completeness (_total/calc)             99.42%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C6     = .          S
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C7     = .          S
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          1

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
  25 ALERT level C = Check and explain
   6 ALERT level G = General alerts; check

   6 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
  20 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

Comment top

Norsesquiterpenes isolated from many ligularia species show some biological activity, such as cytotoxicity (Gao et al., 1998; Fu et al., 2002). Knowledge of the three-dimensioned structure of these compounds is important in order to understand the biosynthetic pathway of terpenes and to establish structure–activity relationships (Kaneko et al., 1982) in this class of compounds.

The molecular backbone of the title compound has a fused tricyclic ring system as shown in Fig. 1. In the structure, the hydrogen attached to O1 forms a strong intermolecular hydrogen bond with the O2, Table 1, forming a one dimensional molecular chain along the b axis (Fig.2).

Related literature top

For background on biological activity, see: Gao & Jia (1998); Fu et al. (2002); Kaneko et al. (1982).

Experimental top

The dried and powdered roots and rhizomes of Ligularia macrophylla (5.0 kg) were extracted with 95% EtOH at reflux temperature three times and filtered. The filtrate was evaporated in vacuo to give a residue (360 g), a portion of which (350 g) was suspended in H₂O (2 L) and partitioned successively with petroleum ether, EtOAc, and n-BuOH. The EtOAc extract (50 g) was subjected to column chromatography on Si gel eluted successively with petroleum ether-acetone (30:1–1:1), the pure compound was obtained from petroleum ether:acetone (5:1).

Structure description top

For background on biological activity, see: Gao & Jia (1998); Fu et al. (2002); Kaneko et al. (1982).

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL.

Figures top

	Fig. 1. The molecular strusture of (I) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. A packing diagram showing the hydrogen bonds in the crystal structure of (I).

4-hydroxy-3-(1-methylethylidene)-6,7,8,8a-tetrahydro-1-oxaacenaphthylen-2-one top

Crystal data top

C₁₄H₁₄O₃	F(000) = 488
M_r = 230.25	D_x = 1.262 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 887 reflections
a = 7.678 (4) Å	θ = 2.7–21.8°
b = 8.063 (4) Å	µ = 0.09 mm⁻¹
c = 19.58 (1) Å	T = 293 K
V = 1212.0 (11) Å³	Prism, colourless
Z = 4	0.18 × 0.15 × 0.10 mm

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	1549 independent reflections
Radiation source: fine-focus sealed tube	1124 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.080
φ and ω scans	θ_max = 27.1°, θ_min = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
T_min = 0.984, T_max = 0.991	k = −10→9
5807 measured reflections	l = −24→19

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)] = 0.080	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.164	H atoms treated by a mixture of independent and constrained refinement
S = 1.20	w = 1/[σ²(F_o²) + (0.0442P)² + 0.5001P] where P = (F_o² + 2F_c²)/3
1549 reflections	(Δ/σ)_max < 0.001
156 parameters	Δρ_max = 0.22 e Å⁻³
1 restraint	Δρ_min = −0.18 e Å⁻³

Crystal data top

C₁₄H₁₄O₃	V = 1212.0 (11) Å³
M_r = 230.25	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 7.678 (4) Å	µ = 0.09 mm⁻¹
b = 8.063 (4) Å	T = 293 K
c = 19.58 (1) Å	0.18 × 0.15 × 0.10 mm

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	1549 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	1124 reflections with I > 2σ(I)
T_min = 0.984, T_max = 0.991	R_int = 0.080
5807 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.080	1 restraint
wR(F²) = 0.164	H atoms treated by a mixture of independent and constrained refinement
S = 1.20	Δρ_max = 0.22 e Å⁻³
1549 reflections	Δρ_min = −0.18 e Å⁻³
156 parameters

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

	x	y	z	U_iso*/U_eq
O1	0.7457 (5)	0.0823 (4)	0.12179 (15)	0.0649 (10)
H1X	0.755 (9)	−0.014 (3)	0.107 (2)	0.09 (2)*
O2	0.7573 (5)	0.7554 (3)	0.08791 (15)	0.0643 (11)
O3	0.7270 (5)	0.7191 (3)	−0.02453 (15)	0.0587 (9)
C1	0.7226 (7)	0.1556 (5)	0.0023 (2)	0.0514 (11)
H1	0.7286	0.0443	−0.0099	0.062*
C2	0.7309 (6)	0.1984 (5)	0.0717 (2)	0.0504 (11)
C3	0.7310 (7)	0.3637 (5)	0.0914 (2)	0.0500 (11)
H3	0.7431	0.3943	0.1370	0.060*
C4	0.7123 (6)	0.4803 (5)	0.0405 (2)	0.0459 (10)
C5	0.6906 (5)	0.4361 (5)	−0.0268 (2)	0.0450 (10)
C6	0.6778 (6)	0.5828 (6)	−0.0707 (2)	0.0499 (11)
H6	0.5557	0.5975	−0.0839	0.060*
C7	0.7851 (6)	0.5607 (6)	−0.1347 (2)	0.0554 (12)
H7	0.9060	0.5393	−0.1213	0.066*
C8	0.7099 (8)	0.4001 (6)	−0.1669 (2)	0.0689 (14)
H8A	0.5875	0.4185	−0.1767	0.083*
H8B	0.7682	0.3815	−0.2102	0.083*
C9	0.7256 (9)	0.2425 (6)	−0.1243 (2)	0.0700 (15)
H9A	0.6370	0.1644	−0.1389	0.084*
H9B	0.8384	0.1924	−0.1328	0.084*
C10	0.7059 (6)	0.2734 (5)	−0.0480 (2)	0.0484 (11)
C11	0.7834 (8)	0.7051 (7)	−0.1837 (2)	0.0679 (14)
C12	0.6172 (10)	0.7755 (10)	−0.2038 (4)	0.128 (3)
H12A	0.5517	0.8041	−0.1638	0.192*
H12B	0.5534	0.6958	−0.2303	0.192*
H12C	0.6367	0.8733	−0.2308	0.192*
C13	0.9324 (6)	0.7596 (4)	−0.21134 (18)	0.130 (3)
H13A	0.9303	0.8436	−0.2439	0.157*
H13B	1.0380	0.7133	−0.1980	0.157*
C14	0.7347 (6)	0.6635 (4)	0.04079 (18)	0.0490 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.091 (3)	0.0379 (16)	0.0657 (19)	0.001 (2)	0.003 (2)	−0.0030 (15)
O2	0.095 (3)	0.0396 (16)	0.0580 (18)	−0.0083 (19)	−0.001 (2)	−0.0081 (14)
O3	0.079 (2)	0.0409 (15)	0.0566 (17)	−0.0037 (17)	−0.0022 (18)	0.0000 (14)
C1	0.052 (3)	0.033 (2)	0.069 (3)	−0.003 (2)	−0.003 (3)	−0.012 (2)
C2	0.049 (3)	0.040 (2)	0.063 (3)	−0.007 (2)	0.001 (2)	0.001 (2)
C3	0.056 (3)	0.046 (2)	0.048 (2)	−0.003 (2)	0.003 (3)	−0.0037 (19)
C4	0.044 (3)	0.041 (2)	0.053 (2)	0.000 (2)	0.004 (2)	−0.0050 (19)
C5	0.037 (2)	0.044 (2)	0.054 (2)	−0.002 (2)	−0.003 (2)	−0.003 (2)
C6	0.047 (3)	0.053 (3)	0.050 (2)	0.001 (2)	−0.009 (2)	−0.001 (2)
C7	0.045 (3)	0.074 (3)	0.046 (2)	0.003 (3)	−0.004 (2)	0.002 (2)
C8	0.074 (4)	0.086 (3)	0.047 (2)	0.004 (3)	−0.001 (3)	−0.016 (3)
C9	0.085 (4)	0.062 (3)	0.063 (3)	0.006 (3)	−0.005 (3)	−0.017 (2)
C10	0.044 (2)	0.048 (2)	0.053 (2)	0.000 (2)	−0.003 (2)	−0.010 (2)
C11	0.063 (3)	0.090 (4)	0.051 (3)	0.002 (3)	−0.007 (3)	0.007 (3)
C12	0.104 (6)	0.164 (8)	0.116 (6)	0.028 (5)	0.001 (4)	0.071 (6)
C13	0.092 (6)	0.169 (9)	0.130 (6)	−0.021 (5)	−0.017 (4)	0.082 (6)
C14	0.053 (3)	0.045 (2)	0.049 (2)	−0.003 (2)	0.001 (3)	−0.0041 (19)

Geometric parameters (Å, º) top

O1—C2	1.361 (5)	C7—C11	1.509 (6)
O1—H1X	0.83 (2)	C7—C8	1.552 (6)
O2—C14	1.196 (4)	C7—H7	0.9800
O3—C14	1.356 (4)	C8—C9	1.524 (6)
O3—C6	1.472 (5)	C8—H8A	0.9700
C1—C10	1.375 (6)	C8—H8B	0.9700
C1—C2	1.402 (6)	C9—C10	1.522 (6)
C1—H1	0.9300	C9—H9A	0.9700
C2—C3	1.387 (6)	C9—H9B	0.9700
C3—C4	1.378 (6)	C11—C13	1.339 (7)
C3—H3	0.9300	C11—C12	1.451 (9)
C4—C5	1.375 (6)	C12—H12A	0.9599
C4—C14	1.487 (5)	C12—H12B	0.9599
C5—C10	1.381 (6)	C12—H12C	0.9599
C5—C6	1.465 (6)	C13—H13A	0.9300
C6—C7	1.509 (6)	C13—H13B	0.9300
C6—H6	0.9800

C2—O1—H1X	113 (4)	C9—C8—H8A	108.2
C14—O3—C6	110.1 (3)	C7—C8—H8A	108.2
C10—C1—C2	121.9 (4)	C9—C8—H8B	108.2
C10—C1—H1	119.1	C7—C8—H8B	108.2
C2—C1—H1	119.1	H8A—C8—H8B	107.4
O1—C2—C3	117.3 (4)	C10—C9—C8	113.1 (4)
O1—C2—C1	122.2 (4)	C10—C9—H9A	109.0
C3—C2—C1	120.5 (4)	C8—C9—H9A	109.0
C4—C3—C2	116.9 (4)	C10—C9—H9B	109.0
C4—C3—H3	121.5	C8—C9—H9B	109.0
C2—C3—H3	121.5	H9A—C9—H9B	107.8
C5—C4—C3	122.0 (4)	C1—C10—C5	116.6 (4)
C5—C4—C14	106.0 (4)	C1—C10—C9	125.6 (4)
C3—C4—C14	131.5 (4)	C5—C10—C9	117.3 (4)
C4—C5—C10	121.6 (4)	C13—C11—C12	120.9 (5)
C4—C5—C6	111.2 (4)	C13—C11—C7	120.1 (5)
C10—C5—C6	126.6 (4)	C12—C11—C7	118.8 (5)
C5—C6—O3	103.0 (3)	C11—C12—H12A	109.5
C5—C6—C7	110.8 (4)	C11—C12—H12B	109.5
O3—C6—C7	117.2 (4)	H12A—C12—H12B	109.5
C5—C6—H6	108.5	C11—C12—H12C	109.5
O3—C6—H6	108.5	H12A—C12—H12C	109.5
C7—C6—H6	108.5	H12B—C12—H12C	109.5
C11—C7—C6	115.6 (4)	C11—C13—H13A	120.0
C11—C7—C8	112.5 (4)	C11—C13—H13B	120.0
C6—C7—C8	103.4 (4)	H13A—C13—H13B	120.0
C11—C7—H7	108.3	O2—C14—O3	121.9 (3)
C6—C7—H7	108.3	O2—C14—C4	129.5 (4)
C8—C7—H7	108.3	O3—C14—C4	108.6 (3)
C9—C8—C7	116.4 (4)

C10—C1—C2—O1	179.3 (4)	C6—C7—C8—C9	−61.5 (6)
C10—C1—C2—C3	−3.2 (8)	C7—C8—C9—C10	35.3 (7)
O1—C2—C3—C4	−178.7 (4)	C2—C1—C10—C5	−2.5 (7)
C1—C2—C3—C4	3.7 (7)	C2—C1—C10—C9	169.3 (5)
C2—C3—C4—C5	1.4 (7)	C4—C5—C10—C1	7.7 (7)
C2—C3—C4—C14	−168.7 (5)	C6—C5—C10—C1	177.6 (4)
C3—C4—C5—C10	−7.4 (7)	C4—C5—C10—C9	−164.8 (5)
C14—C4—C5—C10	165.0 (4)	C6—C5—C10—C9	5.1 (7)
C3—C4—C5—C6	−178.7 (4)	C8—C9—C10—C1	−176.7 (5)
C14—C4—C5—C6	−6.4 (5)	C8—C9—C10—C5	−4.9 (7)
C4—C5—C6—O3	10.2 (5)	C6—C7—C11—C13	134.4 (5)
C10—C5—C6—O3	−160.6 (5)	C8—C7—C11—C13	−107.1 (5)
C4—C5—C6—C7	136.4 (4)	C6—C7—C11—C12	−49.9 (7)
C10—C5—C6—C7	−34.4 (6)	C8—C7—C11—C12	68.6 (7)
C14—O3—C6—C5	−10.4 (4)	C6—O3—C14—O2	−173.4 (5)
C14—O3—C6—C7	−132.3 (4)	C6—O3—C14—C4	7.0 (5)
C5—C6—C7—C11	−179.4 (4)	C5—C4—C14—O2	−180.0 (5)
O3—C6—C7—C11	−61.6 (5)	C3—C4—C14—O2	−8.7 (10)
C5—C6—C7—C8	57.2 (4)	C5—C4—C14—O3	−0.5 (6)
O3—C6—C7—C8	175.0 (4)	C3—C4—C14—O3	170.9 (5)
C11—C7—C8—C9	173.0 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1X···O2ⁱ	0.83 (2)	1.90 (2)	2.719 (4)	170 (5)

Symmetry code: (i) x, y−1, z.

Experimental details

Crystal data
Chemical formula	C₁₄H₁₄O₃
M_r	230.25
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	293
a, b, c (Å)	7.678 (4), 8.063 (4), 19.58 (1)
V (Å³)	1212.0 (11)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.18 × 0.15 × 0.10

Data collection
Diffractometer	Bruker SMART APEX CCD area-detector
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.984, 0.991
No. of measured, independent and observed [I > 2σ(I)] reflections	5807, 1549, 1124
R_int	0.080
(sin θ/λ)_max (Å⁻¹)	0.641

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.080, 0.164, 1.20
No. of reflections	1549
No. of parameters	156
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.18

Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2000), SHELXTL.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1X···O2ⁱ	0.83 (2)	1.90 (2)	2.719 (4)	170 (5)

Symmetry code: (i) x, y−1, z.

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