(1S,2S,6R,7aR)-2-Benzyl-1,6-dihydroxyhexahydropyrrolizin-3-one

In the title compound, C14H17NO3, the dihedral angles show that the H atoms at two stereocenters are in a trans-diaxial configuration. In the crystal, the molecules are linked by O—H⋯O hydrogen bonds. The absolute configuration of the molecule has been established on the basis of refinement of the Hooft and Flack parameters.

In the title compound, C 14 H 17 NO 3 , the dihedral angles show that the H atoms at two stereocenters are in a trans-diaxial configuration. In the crystal, the molecules are linked by O-HÁ Á ÁO hydrogen bonds. The absolute configuration of the molecule has been established on the basis of refinement of the Hooft and Flack parameters.

Related literature
For a synthetic sequence for the preparation of the title compound, see: de Luna Freire et al. (2011). For the use of this type of compounds as LFA-1 (Lymphocyte Function-Associated Antigen-1) inhibitors, see: Baumann (2007). For a related structure, see: Newton et al. (2004).

Comment
The title compound can be used as a prototype for the development of new inhibitors of LFA-1 (lymphocyte functionassociated antigen 1) with potential application as anti-inflammatory agents (Baumann, 2007). The title compound is a new asymmetric benzyl-pyrrolizidinone which has been synthesized in our laboratory and its crystal structure is presented in this article.
The title compound (

Experimental
The title compound was prepared using a synthetic sequence described in the literature (de Luna Freire et al., 2011) and purified by flash silica gel column chromatography (CH 2 Cl 2 :MeOH -solvent gradient: 0:100 to 97:03) to afford 0.06 g (as a white solid) in 97% yield. It was then recrystallized using the liquid-vapor saturation method, dissolved in ethanol and crystallized with a vapor pressure of a second less polar liquid (ethyl ether), in a closed camera, providing the slow formation of crystals.

Refinement
The H-atoms bonded to C-atoms were included in the refinements at geometrically idealized positions with C-H = 0.95, 0.99 and 1.00 Å, for aryl, methylene and methyne H-atoms, respectively, with and U iso (H) = 1.2 times U eq (C). The Hatoms bonded to O atoms were allowed to refine freely. The Flack parameter was x=0.00 (16) (Flack, 1983). Further analysis of the absolute structure was performed using likelihood methods (Hooft et al., 2008) with PLATON (Spek, 2009). A total of 943 Bijvoet pairs were included in the calculations. The resulting value of the Hooft parameter was y = 0.00 (2), with a probability for an inverted structure smaller than 1x10 -100 . These results indicated that the absolute structure has been correctly assigned.     3404,3232,2987,2936,2897,2871,1670,1447,1416,1375,1300,1263,1222,1175,1121  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 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.