Methyl 2-[(3RS,4RS)-3-phenyl-4-(phenylsulfonyl)isoxazolidin-2-yl]acetate

In the title compound, C18H19NO5S, the five-membered isoxazolidine ring is in a half-chair conformation, and the phenyl rings are oriented at a dihedral angle of 66.53 (3)°. In the crystal, C—H⋯O hydrogen bonds link the molecules into a three-dimensional supramolecular structure. A weak C—H⋯π interaction is also observed between adjacent molecules.

In the title compound, C 18 H 19 NO 5 S, the five-membered isoxazolidine ring is in a half-chair conformation, and the phenyl rings are oriented at a dihedral angle of 66.53 (3) . In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules into a three-dimensional supramolecular structure. A weak C-HÁ Á Á interaction is also observed between adjacent molecules.
The present study was undertaken to ascertain the crystal , structure of the title compound.
In the molecule of the title compound ( Fig. 1) the bond lengths are within normal ranges (Allen et al., 1987). The five- In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 1) link the molecules into a three-dimensional structure, in which they may be effective in the stabilization of the structure. π···π contact between the phenyl rings, Cg1 -Cg2 i [symmetry code: (i) -x, 1/2 + y, 1/2 -z, where Cg1 and Cg2 are the centroids of the rings A and B, respectively] may further stabilize the structure, with centroid-centroid distance of 3.9100 (5) Å. A weak C-H···π interaction (Table 1) has also been observed.
The resultant residue was directly purified by flash chromatography on silica using ethyl acetate as solvent.
Crystallization of the product in ethyl acetate gave a colorless crystalline solid (yield: 92%), m.p.: 400-401 K.  The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The reaction scheme. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.003 Δρ max = 0.44 e Å −3 Δρ min = −0.32 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0182 (13) 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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.