Ethoxy­carbonyl­methyl ursolate

Wei Yang; Hua-ling Luo; Cong-ling Yang; Shu-fan Yin; Ying Li

doi:10.1107/S1600536808039706

. 2008 Nov 29;64(Pt 12):o2498. doi: 10.1107/S1600536808039706

Ethoxycarbonylmethyl ursolate

Wei Yang ^a, Hua-ling Luo ^a, Cong-ling Yang ^a, Shu-fan Yin ^a,^*, Ying Li ^a

PMCID: PMC2960021 PMID: 21581459

Abstract

The title compound, C₃₄H₅₄O₅, was synthesized by the reaction of ursolic acid with ethyl chloroacetate in the presence of DMA. All six-membered rings of the pentacyclic triterpene skeleton adopt chair conformations. In the crystal structure, molecules are linked by intermolecular O—H⋯O hydrogen-bond interactions, forming zigzag chains along the c axis.

Related literature

For the pharmacological activity of ursolic acid, see: Es-saady et al. (1996 ▶); Kashiwada et al. (2000 ▶). For the crystal structure of ursolic acid, see: Simon et al. (1992 ▶). For the synthesis and characterization of the title compound and other ursolic acid derivatives, see: Yang et al. (2008 ▶); Liu et al. (2007 ▶).

Experimental

Crystal data

C₃₄H₅₄O₅
M _r = 542.77
Orthorhombic,
a = 11.624 (3) Å
b = 12.465 (4) Å
c = 21.478 (3) Å
V = 3112.0 (14) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 292 (2) K
0.60 × 0.56 × 0.44 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: none
3435 measured reflections
3116 independent reflections
1818 reflections with I > 2σ(I)
R _int = 0.009
3 standard reflections every 200 reflections intensity decay: 0.8%

Refinement

R[F ² > 2σ(F ²)] = 0.047
wR(F ²) = 0.125
S = 0.97
3116 reflections
362 parameters
H-atom parameters constrained
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Data collection: DIFRAC (Gabe & White, 1993 ▶); cell refinement: DIFRAC; data reduction: NRCVAX (Gabe et al., 1989 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808039706/rz2269sup1.cif

e-64-o2498-sup1.cif^{(30.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808039706/rz2269Isup2.hkl

e-64-o2498-Isup2.hkl^{(152.9KB, 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
O1—H1⋯O3ⁱ	0.82	2.14	2.944 (4)	165

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank Mr Zhi-Hua Mao of Sichuan University for the X-ray data collection.

supplementary crystallographic information

Comment

Ursolic acid, a pentacyclic triterpene existing abundantly in the plant kingdom, has been reported to possess pharmacological activities, such as anti-tumor, anti-inflammatory and anti-HIV activities (Es-saady et al., 1996; Kashiwada et al., 2000). The synthesis and characterization of some derivatives of this compound have been recently reported (Liu et al., 2007). We report herein the crystal structure of the title compound, whose synthetic method has been already reported elsewhere (Yang et al., 2008).

In the molecule of the title compound (Fig.1) bond lengths and angles within the six-membered rings are very similar to those given in the literature for ursolic acid (Simon et al., 1992). The C(sp²)—C(sp²) bond distance (C16—C17) is 1.317 (5) Å, the C(sp³)—C(sp³) bond lengths range from 1.506 (6) Å to 1.592 (5) Å, and the three C(sp³)—C(sp²) bond distances (C17—C18, C16—C23 and C16—C15) are 1.491 (5), 1.528 (5) and 1.545 (5) Å, respectively. The five six-membered rings adopt a chair conformation. The carboxy group at C22 and the methyl groups C7, C9, C14 and C19 are axially oriented, while the hydroxy groups and the methyl groups C8, C28 and C29 are in equatorial positions. The O2–C30–C22–C27 and C2–C30–C22–C21 torsion angles are -72.1 (4) Å and 47.8 Å, respectively. In the crystal packing, intermolecular O—H···O hydrogen bonds (Table 1) link molecules to form zig-zag chains extending along the c axis.

Experimental

To a solution of ursolid acid (456 mg, 1 mmol) in DMF (10 ml) was added K₂CO₃ (300 mg, 2.2 mmol), KI (50 mg, 0.3 mmol) and NEt₃ (0.5 ml). After stirring at room temperature for 10 minutes, a solution of ethyl chlorocetate (0.4 ml, 3 mmol) in DMF was added dropwise, and the reaction monitored by TLC. After completion of the reaction, satured brines and ehtyl acetate were added. The organic layer was separated, washed with water until neutral, dried with Na₂SO₄, filtered and evaporated in vacuo to get the solid title compound. Colourless crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution at room temperature.