Crystal structure of benzyl 3-oxo-2-oxa-5-aza-bicyclo-[2.2.1]heptane-5-carboxyl-ate.

The title compound, C13H13NO4 (also known as N-benzyl-oxycarbonyl-4-hy-droxy-l-proline lactone), crystallizes with two mol-ecules in the asymmetric unit. They have slightly different conformations: the fused ring systems almost overlap, but different C-O-C-C torsion angles for the central chains of -155.5†(2) and -178.6†(2)° lead to different twists for the terminal benzene ring. In the crystal, the mol-ecules are linked by C-H⋯O inter-actions, generating a three-dimensional network. The absolute structure was established based on an unchanging chiral centre in the synthesis.