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.

Crystal structure of (1R,4R)-tert-butyl 3-oxo-2-oxa-5-aza-bicyclo-[2.2.2]octane-5-carboxyl-ate.

In the title compound, C11H17NO4, commonly known as N-tert-but-oxy-carbonyl-5-hy-droxy-d-pipecolic acid lactone, the absolute configuration is (1R,4R) due to the enantiomeric purity of the starting material which remains unchanged during the course of the reaction. In the crystal there no inter-molecular hydrogen bonds.