Crystal structures of two substituted thiazolidine derivatives

In both compounds, namely 2′-ferrocenyl-6′-methyl-6a’-nitro-6′,6a’,6b’,7′,9′,11a’-hexahydro-2H-spiro[acenaphthylene-1,11′-chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazol]-2-one, (I), and 6′-(4-methoxyphenyl)-6a’-nitro-6′,6a’,6b’,7′,9′,11a’-hexahydro-2H-spiro[acenaphthylene-1,11′-chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazol]-2-one, (II), an intramolecular C—H⋯O hydrogen bond forms an S(7) ring motif. In (I), molecules are linked via two different C—H⋯O hydrogen bonds, forming chains along [001] and [100]. In (II), they are linked through C—H⋯O hydrogen bonds, forming dimers with an (10) ring motif while C—H⋯π interactions link the molecules in a head-to-tail fashion, forming chains along the a-axis direction.


Chemical context
There are numerous biologically active molecules with fivemembered rings containing two hetero atoms. Among them, thiazolidines are the most extensively investigated class of compounds (Fun et al., 2011). Thiazolidine derivatives have attracted continuous interest over the years because of their varied biological activities (Shih et al., 2015). The special importance of the thiazolidine ring system derives from the fact that it plays an important role in medicinal chemistry. The presence of a thiazolidine ring in penicillin and related derivatives was the first recognition of its occurrence in nature (Č ačić et al., 2010). Substituted thiazolidine derivatives represent important key intermediates for the synthesis of pharmacologically active drugs. The group has wide range of biological activities such as antifungal, antiproliferative, antiinflammatory, antimalarial, herbicidal, antiviral (Samadhiya et al., 2012), anticonvulsant (Pandey et al., 2011), anticancer and anti-oxidant, and also has interesting antimicrobial activity (influenza). In addition, antidiabetic properties (Majed & Abid, 2015) have been reported. Thiazolidine derivatives exhibit anti-HIV, antituberculotic (Fun et al., 2011), herbicidal, antineoplastic, hypolipidemic and anti-inflammatory activities ISSN 2056-9890 (Vennila et al., 2011). Thiazolidines have many interesting activity profiles, namely as COX-1 inhibitors, inhibitors of the bacterial enzyme MurB, which is a precursor, acting during the biosynthesis of peptidoglycan, non-nucleoside inhibitors of HIV-RT and anti-histaminic agents (Č ačić et al., 2010).
In both compounds, an intramolecular C-HÁ Á ÁO hydrogen bond forms an S(7) ring motif (Figs. 1 and 2; Tables 1 and 2). The molecular structure of (I), showing the atom labelling and displacement ellipsoids drawn at 30% probability level. The C-HÁ Á ÁO contact is shown as a thin dashed line.

Figure 2
The molecular structure of (II), showing the atom labelling and displacement ellipsoids drawn at 30% probability level. The C-HÁ Á ÁO contact is shown as a thin dashed line.

Figure 3
The crystal packing of (I  The crystal packing of (II), showing the R 2 2 (10) ring motif. H atoms not involved in hydrogen bonds have been excluded for clarity.

Figure 5
The compound (II) showing the C-HÁ Á Á interactions linking molecules in a head-to-tail fashion, forming chains running along the a axis. H atoms not involved in hydrogen bonds are omitted for clarity. of the reaction as indicated by TLC, the solvent was evaporated under reduced pressure. The crude product obtained was purified by column chromatography using hexane/EtOAc (8:2) as eluent [Yields: 91% for (I), 88% for (II)].

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The hydrogen atoms were placed in calculated positions with C-H = 0.93-0.98 Å and refined using a riding model with fixed isotropic displacement parameters: U iso (H) = 1.5U eq (C) for the methyl group and U iso (H) = 1.2U eq (C) for the remaining H atoms. Computer programs: APEX2 and SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), ORTEP-3 for Windows (Farrugia, 2012) and PLATON (Spek, 2009 For both compounds, data collection: APEX2 (Bruker, 2008); cell refinement: APEX2 (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015) and PLATON (Spek, 2009  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.