(1′S,12′R,13′S,17′S)-15′,15′-Dimethyl-1,2-dihydro-11′,14′,16′,18′-tetraoxa-7′-azaspiro[indole-3,8′-pentacyclo[10.6.0.02,9.03,7.013,17]octadecane]-2,10′-dione

In the title compound, C22H24N2O6, the indole ring has a twist conformation and the tetrahydro-2H-pyran-2-one ring a half-chair conformation. One of the pyrrolidine rings adopts an envelope conformation on the N atom, while the other has a twist conformation; the ‘butterfly’ angle between their mean planes is 62.98 (11)°. The dioxolane ring adopts a twist conformation and the tetrahydrofuran ring has an envelope conformation on the C atom in the fused tetrahydro-2H-pyran-2-one ring adjacent to the O atom of the tetrahydrofuran ring. The ‘butterfly’ angle between the mean planes of these two five-membered rings is 69.14 (10)°. In the crystal, molecules are linked by N—H⋯O hydrogen bonds, forming chains along the a axis.

( 1 0  In the title compound, C 22 H 24 N 2 O 6 , the indole ring has a twist conformation and the tetrahydro-2H-pyran-2-one ring a halfchair conformation. One of the pyrrolidine rings adopts an envelope conformation on the N atom, while the other has a twist conformation; the 'butterfly' angle between their mean planes is 62.98 (11) . The dioxolane ring adopts a twist conformation and the tetrahydrofuran ring has an envelope conformation on the C atom in the fused tetrahydro-2Hpyran-2-one ring adjacent to the O atom of the tetrahydrofuran ring. The 'butterfly' angle between the mean planes of these two five-membered rings is 69.14 (10) . In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds, forming chains along the a axis.   Table 1 Hydrogen-bond geometry (Å , ).  Indole compounds can be used as bioactive drugs (Stevenson et al., 2000) and have also been proven to display high aldose reductase inhibitory activity (Rajeswaran et al., 1999), and antimicrobial and antifungal activities (Amal Raj et al., 2003).

Related literature
The molecular structure of the title compound is shown in Fig. 1. The indole ring is essentially planar with the maximum deviation from planarity being 0.123 (2) Å for atom C7. Atom O1 deviates from the mean plane of the indole ring by 0.2095 (13) Å. The tetrahydro-2H-pyran-2-one ring (O3/C13-C17) has a half-chair conformation.
In the crystal, molecules are linked via N-H···O hydrogen bonds forming chains propagating along the a axis direction (Table 1 and Fig. 2).
The title compound exhibits structural similarities with a related structure (Jagadeesan et al., 2012).

Refinement
The methine and methylene H atoms were included in calculated positions freely refined. The remainder of the H atoms were included in calculated positions and allowed to ride on their parent atom: C-H = 0.93 -0.96 Å, N-H = 0.86 Å, with U iso = 1.5U eq (C-methyl), and = 1.2U eq (C,N) for other H atoms.    Table 1 for details).   (7) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.