(7R,8S,8aS)-8-Hydroxy-7-phenylperhydroindolizin-3-one

In the title compound, C14H17NO2, the six-membered ring of the indolizine system adopts a chair conformation. In the crystal, molecules form chains parallel to the b axis via intermolecular O—H⋯O hydrogen bonds. The absolute molecular configuration was assigned from the synthesis.

In the title compound, C 14 H 17 NO 2 , the six-membered ring of the indolizine system adopts a chair conformation. In the crystal, molecules form chains parallel to the b axis via intermolecular O-HÁ Á ÁO hydrogen bonds. The absolute molecular configuration was assigned from the synthesis.

Comment
Heterocycles are involved in a wide range of biologically important chemical reactions in living organisms, and therefore they form one of the most important and well investigated classes of organic compounds. One group of heterocycles, indolizines, has received much scientific attention during the recent years. They are known for their use as synthetic dyes (Jaung & Jung, 2003), fluorescent materials (Rotaru et al., 2005;Delattre et al., 2005) and also as key intermediates for the synthesis of indolizine based molecules (Kelin et al., 2001). Indolizines both synthetic and natural have also been ascribed with a number of useful biological activities such as antibacterial, antiviral, antiinflammatory (Nash et al., 1988;Molyneux & James, 1982), testosterone-3&-reductase inhibitors, 5-HT4 receptor antagonists, CNS depressants (Harrell et al., 1970), anti-HIV (Ruprecht et al., 1989), anti-cancer Smith et al., 2007) and have been used for treating cardiovascular ailments (Gupta et al., 2003). For instance, aminoalkyloxybenzenesulfonylindolizine compounds such as fantofarone and butoprozine have been used for the treatment of hypertension, arrhythmia and angina pectoris (Rosseels et al., 1982). Several oxygenated indolizines have been shown to prevent, due to their strong anti-oxidative effects, the initiation of oxidation processes that lead to DNA damage (Oslund et al., 2008;Ostby et al., 2000). Consequently, synthesis of indolizines have attracted considerable attention and a number of synthetic methodologies have been developed for a variety of indolizines, making use of in particular, transition metal catalyzed reactions (Chuprakov & Gevorgyan, 2007;. In addition, indolizines and their derivatives are important in the field of material science owing to their unique photophysical properties. 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 and molecular and crystal structure of the title compound, (I) (Fig.   1). A similar analysis of its enantiomer (the stereochemistry of atom C6 was confirmed as R) has already been published (Švorc et al., 2009). The absolute configuration of (I) was established by the synthesis and is depicted in the scheme and Fig. 1. The expected stereochemistry of atoms C5, C6 and C7 was confirmed as S, S and R, respectively (Fig. 1). The central six-membered N-heterocyclic ring is not planar and adopts a chair conformation (Cremer & Pople, 1975). A calculation of least-squares planes shows that this ring is puckered in such a manner that the four atoms C5, C6, C8 and C9 are coplanar to within 0.010 (2) Å, while atoms N1 and C7 are displaced from this plane on opposite sides, with out-of-plane displacements of -0.555 (2) and 0.711 (2) Å, respectively. The phenyl ring attached to the indolizine ring system is planar (mean deviation is 0.009 (2) Å). The N1-C5 and N1-C9 bonds are approximately equivalent (See supplementary material) and both are much longer than the N1-C2 bond. Moreover, the N1 atom is sp 2 hybridized, as evidenced by the sum of the valence angles around it [359.9 (2)°]. 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 1.236 (2) Å, respectively, is somewhat longer than typical carbonyl bonds. This may be due to the fact that atom O1 participates as acceptor in intermolecular hydrogen bonds with atom O2 as a donor. These intermolecular O-H···O hydrogen bonds link the molecules of (I) into extended chains, which run parallel to the b axis ( Fig. 2) and help to stabilize the crystal structure of the compound. Bond lengths and angles in the indolizine ring system are in good agreement with values from the literature (Camus et al., 2003;Lokaj et al., 1999).

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93-0.98 Å and O-H distance 0.85 Å and U iso set at 1.2U eq of the parent atom. The absolute configuration could not be reliably determined for this compound using Mo radiation, and has been assigned according to the synthesis; Friedel pairs have been merged. Fig. 1. Molecular structure of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level (Brandenburg, 2001). Fig. 2. A packing of the molecule of (I), viewed along the b axis.

Special details
Experimental 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 > σ(F 2 ) is used only for calculating Rfactors(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 C2 0.2640 (2