1-Benzyl-5-methoxy-2′,3-dimethyl-4,6-dioxa-2-azaspiro[bicyclo[3.2.0]hept-2-ene-7,4′-isoquinoline]-1′,3′(2′H,4′H)-dione

In the isoquinoline ring system of the title molecule, C22H20N2O5, the N-heterocyclic ring is in a half-boat conformation. The dioxa-2-azaspiro ring is essentially planar [maximum deviation = 0.026 (1) Å] and forms dihedral angles of 22.53 (5) and 64.46 (5)° with the benzene and phenyl rings, respectively. The molecular structure is stabilized by a weak intramolecular C—H⋯O hydrogen bond, which generates an S(7) ring motif. In the crystal, molecules are linked via weak intermolecular C—H⋯O and C—H⋯N hydrogen bonds into layers parallel to (102).

In the isoquinoline ring system of the title molecule, C 22 H 20 N 2 O 5 , the N-heterocyclic ring is in a half-boat conformation. The dioxa-2-azaspiro ring is essentially planar [maximum deviation = 0.026 (1) Å ] and forms dihedral angles of 22.53 (5) and 64.46 (5) with the benzene and phenyl rings, respectively. The molecular structure is stabilized by a weak intramolecular C-HÁ Á ÁO hydrogen bond, which generates an S(7) ring motif. In the crystal, molecules are linked via weak intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds into layers parallel to (102).

Comment
Isoquinoline-1,3,4-trione derivatives were reported to be a type of small molecular inhibitor against caspase-3 which can promote apoptosis of the cells (Du et al., 2008;Chen et al., 2006). Compounds containing an oxazole moiety have been found to inhibit the activity of malignant tumors (Harris et al., 2005). Since many natural products especially the alkaloids containing isoquinoline or oxazole ring are bioactive, there has been intense interest in building frameworks containing isoquinoline moieties with an oxazole group (Yu et al., 2010;Zhang et al., 2004;Wang et al., 2010). The title compound was derived from photocycloaddition of isoquinoline-1,3,4-trione and oxazole (Huang et al., 2011). Since it may have a potential use in biochemical and pharmaceutical fields, we report in this paper the crystal structure of the title compound with a relative configuration of (1S * , 4'S * , 5R * ).

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 -0.97 Å and U iso (H) = 1.2 or 1.5 U eq (C). A rotating-group model was applied for the methyl groups. The highest residual electron density peak is located at 0.75 Å from C1 and the deepest hole is located at 0.59 Å from C10. Fig. 1. The molecular structure of the title compound showing 50% probability displacement ellipsoids for non-H atoms. A weak intramolecular hydrogen bond is shown as a dashed line.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(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.