supplementary materials

Indolizines, the nitrogen containing heterocyclic systems, are widely distributed in nature; in particular, indolizine derivatives are an important class of heterocyclic bioactive compounds with a wide range of applications, such as pharmaceutical drugs, potential central nervous system depressants, calcium entry blockers, cardiovascular agents, spectral sensitizers and novel dyes (Gubin et al., 1992; Gupta et al., 2003; Poty et al., 1994; Hema et al., 2003). Polycyclic indolizine derivatives have been found to have high-efficiency long-wavelength fluorescence quantum yield (Vlahovici et al., 2002). Several polyhydroxylated indolizines are interesting as inhibitors of glycosides (Hempel et al., 1993; Brandi et al., 1995). They have also been tested as antimycobacterial agents against mycobacterial tuberculosis (Gundersen et al., 2003), for the treatment of angina pectoris (Rosseels et al., 1982), aromatase inhibitory (Sonnet et al., 2000), antiinflammatory (Malonne et al., 1998), antiviral (Medda et al., 2003), analgestic (Campagna et al., 1990) and antitumor (Pearson & Guo, 2001) activities. The other well known pharmacological applications associated with this ring compounds are well documented in the literature (Couture et al., 2000; Jorgensen et al., 2000). These findings had led to a spate of synthetic and structural studies of various indolizine analogues.

Based on these facts and in continutation of our interest in developing simple and efficient routes for the synthesis of novel indolizine derivatives, we report here the synthesis, molecular and crystal structure of the title compound, (I). The absolute configuration is known from the synthesis and is depicted in the scheme and Figure 1. The expected stereochemistry of atom C5 was confirmed as S. The central N-heterocyclic ring is not planar and adopts an envelope conformation (Nardelli, 1983). A calculation of least-squares planes shows that this ring is puckered in such a manner that the five atoms N1, C11, C10, C7 and C6 are coplanar to within 0.032 (3) Å, while atom C5 is displaced from this plane with out-of-plane displacement of 0.533 (2) Å. The fused thieno ring is nearly coplanar [mean deviation = 0.007 (2) Å]. The oxopyrrolidine ring attached to the indolizine ring system has flat-envelope conformation with atom C5 on the flap. The deviation of atom C5 from the mean plane of the remaining four atoms N1/C2/C3/C4 is 0.339 (3) Å. The N1—C5 and N1—C11 bonds are approximately equivalent and both are much longer than the N1—C2 bond. Moreover, the N1 atom is sp² hybridized, as evidenced by the sum of the valence angles around it [356.1 (1)°]. These data are consistent with conjugation of the lone-pair electrons on N1 with the adjacent carbonyl and agree with literature values for simple amides (Brown & Corbridge, 1954; Pedersen, 1967). The bond length of the carbonyl group C2=O1 is 1.224 (2) Å, respectively, is somewhat longer than typical carbonyl bonds. This may be due to the fact that atom O1 participates in intermolecular C–H···O hydrogen bonds with atom C9 (Table 2). The bond lengths and angles in the molecule are comparable with those in a related structure (Vrábel et al., 2004,Švorc et al., 2007).