Pregna-1,4,16-triene-3,20-dione

Wang, N.-Q.; Wang, T.-J.

doi:10.1107/S1600536807036732

Pregna-1,4,16-triene-3,20-dione

In the title steroid compound, C₂₁H₂₆O₂, ring A is essentially planar due to the presence of two C=C bonds [1.326 (3) and 1.332 (3) Å]. Rings B and C have regular chair conformations, while ring D has an envelope conformation. Weak intermolecular C—H

O hydrogen bonds stabilize the crystal packing.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807036732/cv2284sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536807036732/cv2284Isup2.hkl Contains datablock I

CCDC reference: 657887

checkCIF report

Key indicators

Single-crystal X-ray study
T = 296 K
Mean (C-C) = 0.003 Å
R factor = 0.040
wR factor = 0.102
Data-to-parameter ratio = 10.7

checkCIF/PLATON results

No syntax errors found



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           27.49
           From the CIF: _reflns_number_total               2274
           Count of symmetry unique reflns         2289
           Completeness (_total/calc)             99.34%
           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
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C8     = .          R
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C9     = .          S
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C10    = .          S
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C13    = .          S
PLAT791_ALERT_1_G Confirm the Absolute Configuration of C14    = .          S

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

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

Comment top

The title compound, (I), is used in the synthesis of prednisolone, because the ring A is fully functionalized a 1,4-dien-3-one system (Nitta et al., 1985). We present here its crystal structure, which exhibits the crystal packing close to those observed in 17α-hydroxy-4-pregnen-20-yn-3-one (II) (Reisch et al., 1993) and 17α-hydroxypregna-1,4-diene-3,20-dione (III) (Sheng et al., 2007). In (I) (Fig. 1), all bond lengths and angles agree with those in (II) and (III). The C1═C2, C4═C5, C16═C17, O1—C3 and O2—C18 distances are 1.326 (3) Å, 1.332 (3) Å, 1.332 (3) Å, 1.226 (3) Å and 1.221 (2) Å, respectively.

Ring A and atoms O1 and C6 are almost coplanar with the r.m.s. deviation of 0.061 (1) Å. Rings B and C show normal chair conformations, which are very similar to those reported by Xia et al. (2005). Ring D has an envelope conformation with atom C14 deviating at 0.589 (3) Å from the mean plane C13/C15/C16/C17 [in spite of structures (II) and (III) with the most deviating atom C13].

In the crystal, the weak intermolecular C—H···O hydrogen bonds (Table 1) stabilize the packing (Fig. 2).

Related literature top

For literature describing similar structures with similar properties to the title compound, see: Nitta et al. (1985); Reisch et al. (1993); Sheng et al. (2007); Xia et al. (2005).

For related literature, see: Patil et al. (2002).

Experimental top

Pregna-1,4,16-triene-3,20-dione was synthesized according to Patil et al. (2002) in a form of a powder. Crystals of (I) suitable for structure analysis were obtained by slow evaporation from a mixture of tetrahydrofuran, acetone and water (4:4:2, v/v).

Structure description top

In the crystal, the weak intermolecular C—H···O hydrogen bonds (Table 1) stabilize the packing (Fig. 2).

For literature describing similar structures with similar properties to the title compound, see: Nitta et al. (1985); Reisch et al. (1993); Sheng et al. (2007); Xia et al. (2005).

For related literature, see: Patil et al. (2002).

Computing details top

Data collection: APEX2 (Bruker, ????); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2003); program(s) used to refine structure: SHELXTL; molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL.

Figures top

	Fig. 1. The structure of (I) with 30% probability displacement ellipsoids.
	Fig. 2. Packing diagram of (I), viewed along the b axis. Hydrogen- bonds are shown as dashed lines.

Pregna-1,4,16-triene-3,20-dione top

Crystal data top

C₂₁H₂₆O₂	F(000) = 672
M_r = 310.42	D_x = 1.199 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 3759 reflections
a = 6.3625 (12) Å	θ = 3.2–26.9°
b = 11.745 (2) Å	µ = 0.08 mm⁻¹
c = 23.007 (4) Å	T = 296 K
V = 1719.2 (5) Å³	Block, pale yellow
Z = 4	0.25 × 0.20 × 0.15 mm

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	2274 independent reflections
Radiation source: fine-focus sealed tube	1871 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.028
φ and ω scans	θ_max = 27.5°, θ_min = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→6
T_min = 0.981, T_max = 0.999	k = −15→12
10912 measured reflections	l = −26→29

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.040	w = 1/[σ²(F_o²) + (0.0456P)² + 0.2215P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.102	(Δ/σ)_max = 0.001
S = 1.05	Δρ_max = 0.15 e Å⁻³
2274 reflections	Δρ_min = −0.13 e Å⁻³
212 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0073 (16)
Primary atom site location: structure-invariant direct methods	Absolute structure: see text
Secondary atom site location: difference Fourier map

Crystal data top

C₂₁H₂₆O₂	V = 1719.2 (5) Å³
M_r = 310.42	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 6.3625 (12) Å	µ = 0.08 mm⁻¹
b = 11.745 (2) Å	T = 296 K
c = 23.007 (4) Å	0.25 × 0.20 × 0.15 mm

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	2274 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	1871 reflections with I > 2σ(I)
T_min = 0.981, T_max = 0.999	R_int = 0.028
10912 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.102	H-atom parameters constrained
S = 1.05	Δρ_max = 0.15 e Å⁻³
2274 reflections	Δρ_min = −0.13 e Å⁻³
212 parameters	Absolute structure: see text

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	0.9371 (4)	0.57024 (18)	0.48495 (8)	0.1004 (7)
O2	1.2908 (3)	0.79394 (18)	0.91843 (8)	0.0839 (6)
C1	1.0192 (4)	0.7610 (2)	0.60194 (9)	0.0619 (6)
H1	1.1142	0.8176	0.6123	0.074*
C2	1.0551 (4)	0.7048 (3)	0.55291 (10)	0.0723 (7)
H2	1.1738	0.7224	0.5311	0.087*
C3	0.9126 (5)	0.6160 (2)	0.53236 (10)	0.0683 (7)
C4	0.7407 (4)	0.5879 (2)	0.57074 (9)	0.0625 (6)
H4	0.6524	0.5281	0.5603	0.075*
C5	0.7016 (3)	0.64276 (17)	0.62024 (9)	0.0501 (5)
C6	0.5246 (4)	0.6074 (2)	0.65934 (9)	0.0617 (6)
H6A	0.4533	0.5420	0.6427	0.074*
H6B	0.4237	0.6690	0.6625	0.074*
C7	0.6068 (4)	0.57713 (18)	0.71942 (9)	0.0551 (6)
H7A	0.6922	0.5089	0.7168	0.066*
H7B	0.4891	0.5609	0.7449	0.066*
C8	0.7380 (3)	0.67328 (16)	0.74551 (8)	0.0428 (4)
H8	0.6477	0.7398	0.7515	0.051*
C9	0.9196 (3)	0.70629 (16)	0.70402 (8)	0.0406 (4)
H9	1.0036	0.6371	0.6987	0.049*
C10	0.8374 (3)	0.74005 (16)	0.64175 (8)	0.0461 (5)
C11	1.0676 (3)	0.79469 (18)	0.73120 (8)	0.0506 (5)
H11A	0.9940	0.8668	0.7341	0.061*
H11B	1.1869	0.8057	0.7055	0.061*
C12	1.1488 (3)	0.76146 (18)	0.79171 (9)	0.0500 (5)
H12A	1.2393	0.6953	0.7886	0.060*
H12B	1.2309	0.8235	0.8078	0.060*
C13	0.9649 (3)	0.73475 (15)	0.83207 (8)	0.0431 (5)
C14	0.8354 (3)	0.63945 (16)	0.80305 (8)	0.0437 (4)
H14	0.9376	0.5799	0.7934	0.052*
C15	0.7042 (4)	0.5901 (2)	0.85305 (9)	0.0614 (6)
H15A	0.5775	0.6341	0.8598	0.074*
H15B	0.6674	0.5111	0.8462	0.074*
C16	0.8584 (4)	0.60245 (19)	0.90194 (9)	0.0605 (6)
H16	0.8498	0.5619	0.9366	0.073*
C17	1.0091 (4)	0.67786 (17)	0.89034 (8)	0.0491 (5)
C18	1.1800 (4)	0.7120 (2)	0.92989 (9)	0.0596 (6)
C19	1.2148 (5)	0.6444 (3)	0.98430 (10)	0.0841 (9)
H19A	1.3263	0.6782	1.0065	0.126*
H19B	1.2521	0.5677	0.9743	0.126*
H19C	1.0882	0.6439	1.0070	0.126*
C20	0.8361 (4)	0.84353 (17)	0.84474 (9)	0.0583 (6)
H20A	0.9170	0.8938	0.8689	0.087*
H20B	0.7084	0.8233	0.8644	0.087*
H20C	0.8031	0.8811	0.8088	0.087*
C21	0.7052 (4)	0.85114 (18)	0.64361 (10)	0.0650 (7)
H21A	0.6380	0.8624	0.6067	0.098*
H21B	0.7956	0.9146	0.6518	0.098*
H21C	0.6004	0.8451	0.6735	0.098*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.1292 (18)	0.1085 (15)	0.0636 (11)	0.0078 (15)	0.0199 (12)	−0.0263 (10)
O2	0.0872 (14)	0.0929 (13)	0.0717 (11)	−0.0241 (13)	−0.0179 (10)	0.0001 (10)
C1	0.0630 (14)	0.0734 (15)	0.0493 (11)	−0.0159 (13)	−0.0024 (11)	0.0101 (11)
C2	0.0675 (16)	0.0992 (19)	0.0502 (12)	−0.0030 (16)	0.0145 (12)	0.0093 (13)
C3	0.0827 (18)	0.0691 (15)	0.0532 (13)	0.0111 (15)	0.0042 (13)	−0.0050 (11)
C4	0.0750 (16)	0.0569 (13)	0.0555 (13)	−0.0038 (13)	−0.0047 (12)	−0.0082 (11)
C5	0.0515 (12)	0.0496 (11)	0.0492 (11)	0.0004 (10)	−0.0050 (10)	−0.0017 (9)
C6	0.0530 (13)	0.0698 (14)	0.0623 (13)	−0.0163 (12)	−0.0024 (11)	−0.0081 (11)
C7	0.0536 (13)	0.0549 (12)	0.0568 (12)	−0.0154 (11)	0.0062 (11)	−0.0041 (10)
C8	0.0406 (10)	0.0383 (9)	0.0495 (10)	0.0017 (8)	0.0049 (9)	−0.0015 (8)
C9	0.0394 (10)	0.0378 (9)	0.0445 (9)	0.0014 (8)	0.0026 (8)	−0.0013 (8)
C10	0.0500 (11)	0.0430 (10)	0.0454 (10)	−0.0014 (9)	0.0001 (9)	−0.0007 (8)
C11	0.0497 (12)	0.0530 (11)	0.0491 (10)	−0.0129 (10)	0.0044 (9)	0.0033 (9)
C12	0.0463 (11)	0.0536 (11)	0.0500 (10)	−0.0088 (10)	−0.0002 (10)	−0.0008 (9)
C13	0.0456 (11)	0.0382 (10)	0.0455 (10)	0.0003 (9)	0.0034 (9)	−0.0024 (8)
C14	0.0454 (11)	0.0385 (9)	0.0473 (10)	−0.0009 (9)	0.0058 (9)	0.0005 (8)
C15	0.0670 (14)	0.0599 (13)	0.0573 (13)	−0.0170 (12)	0.0088 (12)	0.0069 (10)
C16	0.0737 (15)	0.0613 (13)	0.0464 (11)	−0.0033 (13)	0.0053 (12)	0.0078 (10)
C17	0.0565 (12)	0.0463 (11)	0.0445 (10)	0.0069 (10)	0.0050 (10)	−0.0010 (9)
C18	0.0605 (14)	0.0669 (14)	0.0514 (12)	0.0079 (13)	−0.0024 (11)	−0.0064 (11)
C19	0.091 (2)	0.103 (2)	0.0587 (14)	0.0107 (19)	−0.0158 (15)	0.0070 (14)
C20	0.0707 (14)	0.0453 (11)	0.0588 (12)	0.0101 (11)	0.0014 (12)	−0.0061 (9)
C21	0.0818 (17)	0.0492 (12)	0.0641 (13)	0.0098 (13)	−0.0145 (13)	0.0035 (10)

Geometric parameters (Å, º) top

O1—C3	1.226 (3)	C11—H11A	0.9700
O2—C18	1.221 (3)	C11—H11B	0.9700
C1—C2	1.326 (3)	C12—C13	1.526 (3)
C1—C10	1.496 (3)	C12—H12A	0.9700
C1—H1	0.9300	C12—H12B	0.9700
C2—C3	1.461 (4)	C13—C17	1.524 (3)
C2—H2	0.9300	C13—C14	1.542 (3)
C3—C4	1.444 (4)	C13—C20	1.545 (3)
C4—C5	1.332 (3)	C14—C15	1.535 (3)
C4—H4	0.9300	C14—H14	0.9800
C5—C6	1.500 (3)	C15—C16	1.499 (3)
C5—C10	1.516 (3)	C15—H15A	0.9700
C6—C7	1.520 (3)	C15—H15B	0.9700
C6—H6A	0.9700	C16—C17	1.332 (3)
C6—H6B	0.9700	C16—H16	0.9300
C7—C8	1.527 (3)	C17—C18	1.473 (3)
C7—H7A	0.9700	C18—C19	1.499 (3)
C7—H7B	0.9700	C19—H19A	0.9599
C8—C14	1.515 (3)	C19—H19B	0.9599
C8—C9	1.548 (3)	C19—H19C	0.9599
C8—H8	0.9800	C20—H20A	0.9599
C9—C11	1.535 (3)	C20—H20B	0.9599
C9—C10	1.576 (3)	C20—H20C	0.9599
C9—H9	0.9800	C21—H21A	0.9599
C10—C21	1.553 (3)	C21—H21B	0.9599
C11—C12	1.535 (3)	C21—H21C	0.9599

C2—C1—C10	124.9 (2)	C13—C12—C11	110.24 (17)
C2—C1—H1	117.6	C13—C12—H12A	109.6
C10—C1—H1	117.6	C11—C12—H12A	109.6
C1—C2—C3	121.6 (2)	C13—C12—H12B	109.6
C1—C2—H2	119.2	C11—C12—H12B	109.6
C3—C2—H2	119.2	H12A—C12—H12B	108.1
O1—C3—C4	122.7 (3)	C17—C13—C12	118.94 (18)
O1—C3—C2	121.5 (3)	C17—C13—C14	99.28 (15)
C4—C3—C2	115.8 (2)	C12—C13—C14	107.19 (15)
C5—C4—C3	123.6 (2)	C17—C13—C20	107.12 (15)
C5—C4—H4	118.2	C12—C13—C20	110.57 (16)
C3—C4—H4	118.2	C14—C13—C20	113.46 (17)
C4—C5—C6	121.2 (2)	C8—C14—C15	122.14 (18)
C4—C5—C10	122.5 (2)	C8—C14—C13	113.99 (15)
C6—C5—C10	116.17 (17)	C15—C14—C13	103.89 (15)
C5—C6—C7	110.57 (19)	C8—C14—H14	105.1
C5—C6—H6A	109.5	C15—C14—H14	105.1
C7—C6—H6A	109.5	C13—C14—H14	105.1
C5—C6—H6B	109.5	C16—C15—C14	99.80 (18)
C7—C6—H6B	109.5	C16—C15—H15A	111.8
H6A—C6—H6B	108.1	C14—C15—H15A	111.8
C6—C7—C8	111.90 (17)	C16—C15—H15B	111.8
C6—C7—H7A	109.2	C14—C15—H15B	111.8
C8—C7—H7A	109.2	H15A—C15—H15B	109.5
C6—C7—H7B	109.2	C17—C16—C15	112.64 (18)
C8—C7—H7B	109.2	C17—C16—H16	123.7
H7A—C7—H7B	107.9	C15—C16—H16	123.7
C14—C8—C7	111.90 (16)	C16—C17—C18	126.1 (2)
C14—C8—C9	107.43 (16)	C16—C17—C13	109.56 (19)
C7—C8—C9	110.53 (15)	C18—C17—C13	124.0 (2)
C14—C8—H8	109.0	O2—C18—C17	120.5 (2)
C7—C8—H8	109.0	O2—C18—C19	120.8 (2)
C9—C8—H8	109.0	C17—C18—C19	118.7 (2)
C11—C9—C8	112.10 (15)	C18—C19—H19A	109.5
C11—C9—C10	113.81 (16)	C18—C19—H19B	109.5
C8—C9—C10	112.09 (16)	H19A—C19—H19B	109.5
C11—C9—H9	106.0	C18—C19—H19C	109.5
C8—C9—H9	106.0	H19A—C19—H19C	109.5
C10—C9—H9	106.0	H19B—C19—H19C	109.5
C1—C10—C5	111.39 (17)	C13—C20—H20A	109.5
C1—C10—C21	107.31 (18)	C13—C20—H20B	109.5
C5—C10—C21	109.50 (18)	H20A—C20—H20B	109.5
C1—C10—C9	109.97 (17)	C13—C20—H20C	109.5
C5—C10—C9	107.24 (15)	H20A—C20—H20C	109.5
C21—C10—C9	111.48 (16)	H20B—C20—H20C	109.5
C9—C11—C12	113.82 (16)	C10—C21—H21A	109.5
C9—C11—H11A	108.8	C10—C21—H21B	109.5
C12—C11—H11A	108.8	H21A—C21—H21B	109.5
C9—C11—H11B	108.8	C10—C21—H21C	109.5
C12—C11—H11B	108.8	H21A—C21—H21C	109.5
H11A—C11—H11B	107.7	H21B—C21—H21C	109.5

C10—C1—C2—C3	1.2 (4)	C8—C9—C11—C12	51.8 (2)
C1—C2—C3—O1	174.3 (3)	C10—C9—C11—C12	−179.63 (17)
C1—C2—C3—C4	−4.4 (4)	C9—C11—C12—C13	−54.3 (2)
O1—C3—C4—C5	−174.4 (3)	C11—C12—C13—C17	168.19 (16)
C2—C3—C4—C5	4.3 (4)	C11—C12—C13—C14	56.8 (2)
C3—C4—C5—C6	−178.0 (2)	C11—C12—C13—C20	−67.3 (2)
C3—C4—C5—C10	−1.0 (4)	C7—C8—C14—C15	−52.3 (2)
C4—C5—C6—C7	121.5 (2)	C9—C8—C14—C15	−173.83 (17)
C10—C5—C6—C7	−55.8 (3)	C7—C8—C14—C13	−178.48 (16)
C5—C6—C7—C8	54.0 (3)	C9—C8—C14—C13	60.0 (2)
C6—C7—C8—C14	−175.12 (18)	C17—C13—C14—C8	172.40 (16)
C6—C7—C8—C9	−55.4 (2)	C12—C13—C14—C8	−63.3 (2)
C14—C8—C9—C11	−52.2 (2)	C20—C13—C14—C8	59.1 (2)
C7—C8—C9—C11	−174.52 (17)	C17—C13—C14—C15	37.2 (2)
C14—C8—C9—C10	178.41 (15)	C12—C13—C14—C15	161.49 (17)
C7—C8—C9—C10	56.1 (2)	C20—C13—C14—C15	−76.2 (2)
C2—C1—C10—C5	2.1 (3)	C8—C14—C15—C16	−165.34 (18)
C2—C1—C10—C21	−117.7 (3)	C13—C14—C15—C16	−34.8 (2)
C2—C1—C10—C9	120.9 (2)	C14—C15—C16—C17	19.4 (3)
C4—C5—C10—C1	−2.3 (3)	C15—C16—C17—C18	178.0 (2)
C6—C5—C10—C1	174.97 (18)	C15—C16—C17—C13	4.5 (3)
C4—C5—C10—C21	116.3 (2)	C12—C13—C17—C16	−141.8 (2)
C6—C5—C10—C21	−66.5 (2)	C14—C13—C17—C16	−26.2 (2)
C4—C5—C10—C9	−122.6 (2)	C20—C13—C17—C16	92.0 (2)
C6—C5—C10—C9	54.6 (2)	C12—C13—C17—C18	44.5 (3)
C11—C9—C10—C1	56.5 (2)	C14—C13—C17—C18	160.17 (19)
C8—C9—C10—C1	−174.94 (16)	C20—C13—C17—C18	−81.6 (2)
C11—C9—C10—C5	177.80 (16)	C16—C17—C18—O2	−168.9 (2)
C8—C9—C10—C5	−53.7 (2)	C13—C17—C18—O2	3.7 (3)
C11—C9—C10—C21	−62.4 (2)	C16—C17—C18—C19	11.1 (3)
C8—C9—C10—C21	66.2 (2)	C13—C17—C18—C19	−176.3 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12B···O2	0.97	2.60	3.076 (3)	111
C19—H19B···O1ⁱ	0.96	2.57	3.356 (4)	139
C21—H21A···O1ⁱⁱ	0.96	2.59	3.537 (3)	169

Symmetry codes: (i) −x+5/2, −y+1, z+1/2; (ii) x−1/2, −y+3/2, −z+1.

Experimental details

Crystal data
Chemical formula	C₂₁H₂₆O₂
M_r	310.42
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	296
a, b, c (Å)	6.3625 (12), 11.745 (2), 23.007 (4)
V (Å³)	1719.2 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.25 × 0.20 × 0.15

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.981, 0.999
No. of measured, independent and observed [I > 2σ(I)] reflections	10912, 2274, 1871
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.102, 1.05
No. of reflections	2274
No. of parameters	212
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.15, −0.13
Absolute structure	See text

Computer programs: APEX2 (Bruker, ????), SAINT (Bruker, 2003), SAINT, SHELXTL (Bruker, 2003), SHELXTL, PLATON (Spek, 2003).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C19—H19B···O1ⁱ	0.96	2.57	3.356 (4)	139
C21—H21A···O1ⁱⁱ	0.96	2.59	3.537 (3)	169

Symmetry codes: (i) −x+5/2, −y+1, z+1/2; (ii) x−1/2, −y+3/2, −z+1.

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