7-Deacetylgedunin

The title compound [systematic name: (1S,3aS,4aR,4bS,5R,6aR,10aR,10bR,12aS)-1-(furan-3-yl)-5-hydroxy-4b,7,7,10a,12a-pentamethyl-4b,5,6,6a,7,10a,10b,11,12,12a-decahydronaphtho[2,1-f]oxireno[2,3-d]isochromene-3,8(1H,3aH)-dione], C26H32O6, which is a limonoid-type triterpene isolated from the seeds of X. moluccensis, crystallizes with three independent molecules with very similar geometries in the asymmetric unit. In each molecule, the four fused six-membered rings of the genudin core adopt distorted half-chair, chair, twist-boat and twisted half-chair conformations. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into helical chains propagated in [100]. Weak non-classical C—H⋯O contacts further consolidate the crystal packing.


7-Deacetylgedunin
W. Ravangpai, T. Theerawattananond, S. Pengpreecha, N. Muangsin and K. Pudhom Comment Limonoid research from the Meliaceae family is of growing interest due to a range of biological activities, such as insect antifeedants and growth regulators, antibacterial, antifungal, antimalarial, anticancer and antiviral activities on humans (Koul et al., 2004;Endo et al., 2002;Nakagawa et al., 2001). Such a focused interest upon limonoids from the family Meliaceae has already resulted in the discovery of several limonoids with novel skeletons, mostly, but not exclusively, from within the genus Xylocarpus, and, in particular, the cannonball mangrove, Xylocarpus granatum Koenig (Wu et al., 2004;Cui et al., 2005;Zhou et al., 2006;Cui et al., 2007;Li et al., 2009;Pudhom et al., 2009). Limonoid derivatives have been found in all Xylocarpus plants studied, but their distribution and content may vary both between different plant species, and between parts or geocultivars of the same species. This, combined with their wide ranging structural diversity and potential biological significance across this plant family, prompted us to investigate another plant in this genus, Xylocarpus moluccensis. Herein, the complete assignments of NMR data and the crystal and molecular structure of 7-deacetylgedunin obtained from the seeds of X. moluccensis, were reported for the first time.
The asymmetric unit of the title compound contains three crystallographically independent molecules. There is very little difference between the bond lengths and angles of these molecules. The molecule consists of four fused six membered rings (A, B, C and D) of genudin core. All the rings are all trans fused and adopt distorted half-chair, chair, twist-boat, and twisted half-chair conformation, respectively. The furan ring is planar and nearly perpendicular orientation to the main plane of the molecule.
In the crystal structure, molecules related by translation along the a axis are linked into chains through O-H···O hydrogen bonds. Weak non-classical C-H···O contacts are also observed in the structure.

Experimental
General Experimental Procedures. Melting point was measured using a Fisher-Johns melting point apparatus. HRESIMS spectrum was obtained using a Bruker micrOTOF mass spectrometer. The NMR spectra were recorded on a Varian YH400 spectrometer at 400 MHz for 1 H NMR and at 100 MHz for 13 C NMR using TMS (tetramethylsilane) as internal standard.
Plant Material. Fruits of X. moluccensis were collected from Phuket Province, Thailand, in December 2009. Plants materials were identified by Royal Forest Department, Bangkok, Thailand.

Refinement
C-bound H atoms were geometrically positioned and treated as riding atoms with distances C-H = 0.96 Å (CH 3 ), 0.97 Å (CH 2 ), 0.93 Å (CH), and U iso (H) = 1.20 U eq (C) for methylene and aromatic, 1.50 U eq (C) for methyl. O-bound H atoms were located on a difference map and refined isotropically. The absolute structure could not be determined from the X-ray analysis, but it was known from earlier work on related compounds (e.g. Pudhom et al., 2009;Mitsui et al., 2006;Waratchareeyakul et al., 2004). 6,498 Friedel pairs were therefore merged before the final refinement. Fig. 1. The molecular structure of the title compound showing 30% probability displacement ellipsoids and the atom-numbering scheme in one independent molecule.

Refinement
Refinement on F 2 H atoms treated by a mixture of independent and constrained refinement Least-squares matrix: full 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 Rfactors(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.