Crystal structure of limonoid TS3, isolated from Trichilia rubescens.

The title limonoid compound, C(26)H(28)O(5)·0.5H(2)O (TS3) [systematic name: (3aS,3bS,4aS,5aS,6S,7aR,8aR,8bS,11aR)-6-(furan-3-yl)-3a,5a,8b,11a-tetra-methyl-3a,4a,5,5a,6,7,7a,8b,11,11a-deca-hydro-oxireno[2',3':4b,5]oxireno[2'',3'':2',3']cyclo-penta-[1',2':7,8]phenanthro[10,1-bc]furan-3(3aH)-one hemihydrate], crystallizes with two independent mol-ecules (1 and 2) in the asymmetric unit and one water mol-ecule. TS3 is composed of three six-membered rings (A, C and D), three five-membered rings (B, E and F) and two epoxide rings. A group of five fused rings (A-E) is bonded to a furan ring (F) with a Csp(3)-Csp(2) bond [1.500†(3)†à in mol-ecule 1 and 1.499†(3)†à in mol-ecule 2]. The absolute structures of the mol-ecules in the crystal were determined by resonant scattering; Flack parameter = 0.05†(5). In the crystal, the individual mol-ecules stack in columns along the b-axis direction. The water mol-ecule bridges mol-ecules 1 and 2 via O(water)-H⋯O and C-H⋯O(water) hydrogen bonds. Together with further C-H⋯O hydrogen bonds, linking mol-ecules 1 and 2, the columns are linked to form slabs parallel to the ab plane. Within each column, mol-ecules are also linked via C-H⋯π inter-actions involving the five-membered furan (F) rings.