Cholest-5-en-3β-yl 3-(4-eth­oxy­phen­yl)prop-2-enoate

Bernhard Bugenhagen; Ariane Munk; Volkmar Vill; Yosef Al-Jasem; Thies Thiemann

doi:10.1107/S160053681202452X

. 2012 Jun 13;68(Pt 7):o2064. doi: 10.1107/S160053681202452X

Cholest-5-en-3β-yl 3-(4-ethoxyphenyl)prop-2-enoate

Bernhard Bugenhagen ^a, Ariane Munk ^b, Volkmar Vill ^b, Yosef Al-Jasem ^c, Thies Thiemann ^d,^*

PMCID: PMC3393328 PMID: 22807885

Abstract

In the asymmetric unit of the title compound, C₃₈H₅₆O₃, there are two symmetry-independent molecules that differ in the rotation angle along the C—O bond between the 3-(4-ethoxyphenyl)prop-2-enoate and cholest-5-en-3β-yl groups by 169.3 (3)°. In both molecules, steroid ring B adopts a half-chair conformation, rings A and C adopt a chair conformation and ring D exists in an envelope form. The two symmetry-independent molecules pack in the crystal into separate layers parallel to (-102) with their long axis parallel to the [201] direction. Short intermolecular C—H⋯O and C—H⋯π contacts are observed.

Related literature

For the preparation of the title compound, see: Thiemann et al. (2011 ▶). For applications of this class of compounds, see: Vora (1976 ▶); Kutulya et al. (1983 ▶); Tanaka et al. (1981 ▶); Dong et al. (2010 ▶). For ring conformational analysis, see: Cremer & Pople (1975 ▶); Siri et al. (2002 ▶).

Experimental

Crystal data

C₃₈H₅₆O₃
M _r = 560.83
Monoclinic,
a = 11.6919 (5) Å
b = 10.5844 (4) Å
c = 27.3230 (11) Å
β = 101.226 (1)°
V = 3316.6 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 100 K
0.25 × 0.08 × 0.07 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.714, T _max = 0.746
45080 measured reflections
7947 independent reflections
7272 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.108
S = 1.06
7947 reflections
751 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.77 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) within OLEX2 (Dolomanov et al., 2009 ▶); molecular graphics: PLATON (Spek, 2009 ▶) and Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S160053681202452X/gk2477sup1.cif

e-68-o2064-sup1.cif^{(61.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681202452X/gk2477Isup2.hkl

e-68-o2064-Isup2.hkl^{(388.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C33B—H33B⋯O2B ⁱ	0.95	2.56	3.389 (3)	145
C37B—H37C⋯O2B ⁱ	0.99	2.59	3.425 (3)	142
C37A—H37B⋯O2A ⁱⁱ	0.99	2.40	3.362 (3)	163

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

Comment

Cholesteryl cinnamates are known to exhibit chiral mesogenic phases. The interest in the influence of the substituents of the cinnamyl unit in these compounds on their phase transition behavior (Vora, 1976; Kutulya et al., 1983) and on their crystal packing at room temperature and below remains unabated, also in view of the possibility of photodimerizing the substances in the crystal (Tanaka et al., 1981; Dong et al., 2010). For the title compound, the authors have observed the following phase transformation sequence: Cr(1) 136.2 Cr(2) 148.9 C h 270 dec., where the numbers denote temperature of the phase transition in °C. The cholesteric phase Ch undergoes decomposition at 270°C. Of special note is the Cr(1)—Cr(2) transition at 136.2°C, which proceeds through a rapid melting of Cr(1) and an immediate solidification to Cr(2). This led the authors to investigate the crystal structure Cr(1) of the compound. In the crystal, there are two symmetry independent molecules A and B that vary in their ring-conformation only slightly but differ in the rotation angle along the C—O ester bond between the 3-(4-ethoxyphenyl)-2-propenoate and cholest-5-en-3β-yl groups by 169.3 (3)°. In both molecules, the π system of the phenylpropenoate unit is almost planar [for A: O1A—C28A– –C31A—C36A = 3.4 (3)° and for B: O1B—C28B– –C31B—C32B = -3.3 (2)°], but the average plane of the phenylpropenoate is tilted by 55.5 (3)° versus the average plane defined by the carbon atoms of ring A of the cholest-5-ene framework for molecule B and by 61.1 (3)° for molecule A. In the crystal, molecules A and molecules B define separate layers parallel to (-1 0 2). Within each layer translation related molecules form columns extended along [2 0 1] with their long molecular axis collinear with this direction. Molecules in the neighbouring columns exhibit head to tail arrangement with C—H···O interactions occurring between the 4-ethoxyphenyl group and propenoate unit (Table 1). These interactions define the strands of molecules extending in the [0 1 0] direction within the layer. The molecules in neighbouring [0 1 0] strands contact via their steroidal fragments and the dihedral angle between the mean planes of the steroidal parts of neighboring molecules is 77.3 (3)° and 83.3 (3)° for molecules A and B, respectively. The neighboring layers are packed in such a manner that contacts are formed only between molecules A and B in a head-to-head arrangement; the dihedral angle between the steroidal mean planes of these contacting molecules is 80.3 (3)°.

A conformational analysis of rings A—D was carried out, using puckering parameters developed by Cremer and Pople (1975) (Table 2). It was found that rings A and C adopt a chair conformation, ring B adopts a half-chair conformation, and ring D adopts an envelope conformation for both molecules A and B (Siri et al., 2002).

Experimental

To a solution of triphenylphosphine (582 mg, 2.2 mmol) in CH₂Cl₂ (7.5 ml) is added bromotrichloromethane (900 mg, 4.5 mmol), and the resulting solution is stirred for 20 min. at rt. Thereafter, 3-(4-ethoxyphenyl)prop-2-enoic acid (4-ethoxycinnamic acid (384 mg, 2.0 mmol) is added, and the solution is heated at 50 °C for 15 min. Cholest-5-en-3β-ol (cholesterol, 386 mg, 1.0 mmol) is added, and after 20 min. Et₃N (200 mg, 2.0 mmol) is added dropwise with the help of a syringe. The reaction mixture is stirred at 45 °C for 12 h. Then, it is cooled, poured into water (30 ml) and extracted with CH₂Cl₂ (3 X 15 ml). The organic phase is washed with 15w% aq. NaOH (15 ml) and subsequently with aq. HCl (1 ml conc. HCl in 7 ml of H₂O), dried over anhydrous MgSO₄, and evaporated in vacuo. Column chromatography of the residue on silica gel (eluent MtBE/hexane/CHCl₃ 1:3:1, R_f = 0.6) gives the target compound (476 mg, 85%) as a colorless solid; νmax (KBr/cm^-1) 2946, 1713, 1631, 1602, 1511, 1469, 1313, 1252, 1163, 1009, 826; δ_H (400 MHz, CDCl₃) 0.68 (3H, s, CH₃), 0.86 (3H, d, ³J = 6.4 Hz, CH₃), 0.87 (3H, d, ³J = 6.8 Hz, CH₃), 0.91 (3H, d, ³J = 6.8 Hz, CH₃), 1.04 (3H, s, CH₃), 1.42 (3H, t, ³J = 7.2 Hz, CH₃), 4.06 (2H, q, ³J = 7.2 Hz), 4.74 (1H, m), 5.40 (1H, m), 6.28 (1H, d, ³J = 16.0 Hz), 6.88 (2H, d, ³J = 8.8 Hz), 7.46 (2H, d, ³J = 8.8 Hz), 7.62 (1H, d, ³J = 16.0 Hz); δ_C (100.5 MHz, CDCl₃) 11.9, 14.7, 18.7, 19.4, 21.0, 22.6, 22.8, 23.8, 24.3, 27.9, 28.0, 28.2, 31.8, 35.8, 36.2, 36.6, 37.0, 38.3, 39.5, 39.7, 42.3, 50.0, 56.1, 56.7, 63.6, 73.9, 114.7 (2 C), 116.0, 122.6, 127.1, 129.7 (2 C), 139.7, 144.2, 160.7, 166.8. The crystal was grown from hot 2-propanol.