9-[(Furan-2-ylmethyl)amino]-5-(3,4,5-trimethoxyphenyl)-5,5a,8a,9-tetrahydrofuro[3′,4′:6,7]naphtho[2,3-d][1,3]dioxol-6(8H)-one

In title compound, C27H27NO8, the dihydrofuran-2(3H)-one ring and the six-membered ring fused to it both display envelope conformations. The dihedral angle between the benzene ring of the benzo[d][1,3]dioxole group and the other benzene ring is 60.59 (2)°. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link the molecules into a three-dimensional network. The furan ring is disordered over two sets of sites with occupancies of 0.722 (7) and 0.278 (7)


Comment
Podophyllotoxin and its derivatives are well known substances with anti-cancer activity. In recent years, our study has been aimed at synthesizing novel podophyllotoxin compounds with improved bioactivities (Lu et al., 2010;Yu et al., 2008;Zhao et al., 2009). In this paper, we report the crystal structure of title the compound.

Experimental
The title compound was synthesized by two steps. A mixture of furan-2-carbaldehyde (0.115 g, 1.2 mmol), 4β-amino podophyllotoxin (0.420 g, 1 mmol) and two drops of acetic acid in 95% ethanol (30 ml) was stirred for 6 h, then an appropriate amount of NaBH 4 was added and the mixture stirred for 1 h at 273 K. After the addition of 5% HCl (5 ml) to end off the reaction, the mixture was concentrated in vacuo and the pH adjusted to basic conditions with a saturated NaHCO 3 solution.
The reaction mixture was extracted with CH 2 Cl 2 , dried over MgSO 4 and concentrated in vacuo. The residue was dissolved in methanol and slow evaporation over two weeks at room temperature gave colourless crystals suitable for X-ray analysis

Refinement
All H atoms bound to C atoms were found in a difference Fourier map, and included in the final cycles of refinement using a riding model, with C-H = 0.95-1.00 Å and with U iso (H) = 1.2U eq (C) for aryl and methylene H atoms and 1.5U eq (C) for the methyl H atoms. The amine H atom was refined freely. 690 Friedel pairs were merged. Similarity restraints in distances and thermal parameters were used in order to attain a reasonable geometry of the disordered furan ring.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 40% probability level.