Crystal structure of methyl 7-phenyl-6a,7,7a,8,9,10-hexahydro-6H,11aH-thiochromeno[3,4-b]pyrrolizine-6a-carboxylate

In the title compound, C22H23NO2S, the inner pyrrolidine ring (A) adopts an envelope conformation with the methine C atom opposite the fused C—N bond as the flap. The thiopyran ring (C) has a half-chair conformation and its mean plane is inclined to the fused benzene ring by 1.74 (11)°, and by 60.52 (11)° to the mean plane of pyrrolidine ring A. In the outer pyrrolidine ring (B), the C atom opposite the fused C—N bond is disordered [site-occupancy ratio = 0.427 (13):0.573 (13)] and both rings have envelope conformations, with the disordered C atom as the flap. The planes of the phenyl ring and the benzene ring of the thiochromane unit are inclined to one another by 65.52 (14)°. In the crystal, molecules are linked by a pair of C—H⋯O hydrogen bonds forming inversion dimers.


Related literature
10 restraints H-atom parameters constrained Á max = 0.21 e Å À3 Á min = À0.21 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). importance because they are the structural elements of many alkaloids. It has been found that they exhibit antifungal activity against various pathogens (Amal Raj et al., 2003). Optically active pyrrolidine derivatives have been used as intermediates in controlled asymmetric synthesis (Suzuki et al., 1994). In view of its biological importance, the crystal structure determination of the title compound was undertaken.
In the crystal, molecules are linked by a pair of C-H···O hydrogen bonds forming inversion dimers (Table 1 and Fig. 2).

S2. Synthesis and crystallization
A solution of methyl (Z)-2-(((2-formylphenyl)thio)methyl)-3-phenyl acrylate (1 mmol) and L-proline(1.2 mmol) in acetonitrile (10ml) was refluxed until the completion of the reaction as evidenced by TLC. The solvent was r removed under vacuum. The crude product was subjected to column chromatography on silica gel (100-200 mesh) using petroleum ether-ethyl acetate (9:1) as eluent, which successfully provided the pure product as colorless solid. The product was dissolved in chloroform and heated for two minutes. The resulting solution was subjected to crystallization by slow evaporation of the solvent for 48 hours resulting in the formation of single crystals.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were fixed geometrically and allowed to ride on their parent C atoms: C-H = 0.93-0.98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The crystal packing of the title compound, viewed along the a axis. Dashed lines shows the intermolecular C-H···O hydrogen bonds (see Table 1). H atoms not involved in hydrogen bonding have been omitted for clarity.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.