Ethyl 10α-hydroxy-4,9-dimethyl-14-oxo-3,8,15-trioxatetracyclo[10.3.0.02,4.07,9]pentadecane-13-spiro-5′-pyrazole-3′-carboxylate

The ten-membered ring in the title molecule adopts an approximate chair–chair conformation, whereas the five-membered furan and pyrazole rings display envelope conformations. The conformation of the molecule is stabilized by six intramolecular hydrogen bonds and crystal cohesion is ensured by five C—H⋯O hydrogen bonds, in addition to C–H⋯π interaction, connecting molecules.

The ten-membered ring in the title molecule, C 25 H 29 ClN 2 O 7 , adopts an approximate chair-chair conformation, whereas the five-membered furan and pyrazole rings display envelope conformations. The mean plane of the furan ring is almost perpendicular to that of the pyrazole ring, as indicated by the dihedral angle between them of 86.45 (9) . The pyrazole ring is slightly inclined to the plane of the attached phenyl ring, subtending a dihedral angle of 16.88 (8) . The conformation of the molecule is stabilized by six intramolecular hydrogen bonds and crystal cohesion is ensured by five C-HÁ Á ÁO hydrogen bonds, in addition to C-HÁ Á Á interactions.

Structure description
Anvillea radiata is an endemic plant that grows in northern Africa, particularly in the two Maghreb countries Morocco and Algeria. It belongs to the Asteraceae family and is widely used in Moroccan and Algerian traditional medicine for the treatment of dysentery and gastrointestinal disorders (Bellakhdar, 1997). It also exhibits hypoglycemic activity (Qureshi et al., 1990), and has been reported to possess antitumoral activity (Abdel Sattar et al.,1996). We have previously shown that the aerial parts of anvillea radiata could be used as a renewable source of 9-hydroxyparthenolide (El Hassany et al., 2004). In order to prepare products with high added value that can be used in the pharmacology and cosmetics industries, we have developed a synthesis of a new spiropyrazole by 1,3-dipolar cycloaddition. Treating 9-hydroxy-1,10-epoxyparthenolide data reports with 1.2 equivalents amount of N-para-chlorophenylhydrazono -bromoglyoxylate at room temperature gives the title compound ethyl 10-hydroxy-4,9-dimethyl-14-oxo-3,8,15trioxatetracyclo[10.3.0.0 2,4 .0 7,9 ]pentadecane-13-spiro-5 0 -pyrazole-3 0 -carboxylate. The structure of this new product was confirmed by single-crystal X-ray diffraction.
The molecule is built up from two fused five-and tenmembered rings, with two additional epoxy ring systems and a 4,5-dihydro-3-phenylpyrazole group as a substituent (Fig. 1). The ten-membered ring adopts an approximate chair-chair conformation, while the pyrazole and the furan rings adopt envelope conformations, with the C13 and C9 atoms as the, respective flaps. The dihedral angle between the mean plan of the pyrazole ring and that of the furan ring is of 86.45 (9) . The phenyl ring is inclined to the plane of the attached furan ring by a dihedral angle of 16.88 (8) . The conformation of the molecule is stabilized by six intramolecular hydrogen bonds ( Fig. 1 and Table 1).
In the crystal, the molecules are linked together through five hydrogen bonds (Table 1) and one C-HÁ Á Á interaction to build an aggregate as shown in Fig. 2. An overall view of the crystal packing is shown in Fig. 3.

Synthesis and crystallization
The title compound was obtained by the treatment of 9hydroxyparthenolide (500 mg) with m-chloroperbenzoic acid (250 mg) in CH 2 Cl 2 (75 ml). The mixture was stirred for Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A projection showing the molecules connected by hydrogen bonds (dashed cyan lines) and a C-HÁ Á Á interaction (dashed green line).

Figure 3
Crystal packing of the title compound showing the molecules stacked approximately along the b axis.

Figure 1
The title molecule with the atom-labelling scheme showing the intramolecular hydrogen bonds (dashed bonds). Displacement ellipsoids are drawn at the 50% probability level.
30 min at room temperature and treated with an aqueous solution of Na 2 CO 3 (10%), then extracted with CH 2 Cl 2 . The residue obtained after evaporation of CH 2 Cl 2 was chromatographed on a silica gel column with hexane-ethyl acetate (60/ 40) as eluent to isolate 350 mg of 9-hydroxy-1,10-epoxyparthenolide. To 300 mg of this compound dissolved in 50 ml of dichloromethane was added 1.2 equivalents of N-parachlorophenylhydrazono -bromoglyoxylate in the presence of 0.3 equivalents of caesium carbonate (Cs 2 CO 3 ). The reaction mixture was stirred at room temperature for 3 h, and then the reaction was stopped by adding water (20 ml) and extracted three times with dichloromethane (3 Â 30 ml). The organic phase was dried over sodium sulfate and then evaporated under vacuum. Chromatography of the residue obtained on silica gel column eluting with hexane ethyl acetate (70/30), allowed us to obtain the title compound in a 94% yield. Crystallization was carried out at room temperature from an ethyl acetate solution (m.p. 438-440 K).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.   Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.