Ethoxycarbonylmethyl ursolate

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.

The title compound, C 34 H 54 O 5 , 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-HÁ Á ÁO hydrogen-bond interactions, forming zigzag chains along the c axis.
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).

Experimental
To a solution of ursolid acid (456 mg, 1 mmol) in DMF (10 ml) was added K 2 CO 3 (300 mg, 2.2 mmol), KI (50 mg, 0.3 mmol) and NEt 3 (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 Na 2 SO 4 , 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.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.98 Å, O-H = 0.82 Å and with U iso (H) = 1.2U eq (C) or 1.5 U eq (C, O) for hydroxy and methyl H atoms. In the absence of significant anomalous dispersion effects, Friedel pairs were merged.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level.