24,4,8-Trioxa-21-aza-1,3,6(1,2)-tribenzena-2(2,3)-bicyclo[3.3.0]octanacyclooctaphane

The crystal structure of the title compound, C26H25NO3, was determined as part of an investigation of host–guest and electron donor–acceptor complexes. The oxazole and the pyrrole rings both adopt envelope conformations. The dihedral angle between the two benzene rings directly linked to the oxazole ring is 49.5 (1)°. The crystal structure is stabilized by a C—H⋯π interaction.

The crystal structure of the title compound, C 26 H 25 NO 3 , was determined as part of an investigation of host-guest and electron donor-acceptor complexes. The oxazole and the pyrrole rings both adopt envelope conformations. The dihedral angle between the two benzene rings directly linked to the oxazole ring is 49.5 (1) . The crystal structure is stabilized by a C-HÁ Á Á interaction.

Comment
The design and synthesis of cyclophanes possessing rigidly defined cavities and shape-persistent structures of molecular dimensions is of interest as molecular hosts in the areas of host-guest and electron donor-acceptor complexes (Diederich, 1991;Cram & Cram, 1994;Morrison & Hoger, 1996). 1,3-Dipolar cycloaddition reactions afford efficient methods for the construction of heterocyclic units in a highly regio-and stereoselective manner (Padwa, 1984). In particular, the chemistry of azomethine ylides has gained significance in recent years as it serves as an expedient route for the construction of nitrogen heterocycles. N and O heterocycles have also been shown to provide useful information about anticancer and antiviral properties (Chiacchio et al., 2003).
The bond lengths (Allen et al., 1987) and bond angles are in agreement with the values reported in literature.

Experimental
To a solution of O,O'-coupled salicylaldehyde (bis aldehyde), using o-xylylene bromide (2 mmol) in dry acetonitrile (20 ml), was added L-proline (1 mmol) under an N 2 atmosphere. The reaction was refluxed for 4 h. After completion of the reaction, the solvent was distilled off under reduced pressure and the crude product was purified by column chromatography.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.98 Å and U iso (H) = 1.2U eq (C).