Andirobin from X. moluccensis

The title compound (systematic name: methyl 2-{(1R,2R)-2-[(1aS,4S,4aS,8aS)-4-(furan-3-yl)-4a-methyl-8-methylene-2-oxooctahydrooxireno[2,3-d]isochromen-7-yl]-2,6,6-trimethyl-5-oxocyclohex-3-en-1-yl}acetate), C27H32O7, was isolated from X. moluccensis seeds from Thailand. The conformations of the six-membered rings are distorted half-chair, chair and half-chair for the isolated cyclohexane, fused cyclohexane and lactone rings, respectively. In addition, the lactone ring bears in an equatorial orientation an essentially planar furan ring (r.m.s. deviation = 0.004 Å), which forms an angle of 63.87 (13)° with the mean plane defined by the ten atoms of the two fused six-membered rings (r.m.s. deviation = 0.213 Å). The absolute configuration was fixed on the basis of literature data.

In the molecular structure, the conformation of the six-membered rings are distorted half-chair, chair and half-chair for the isolated cyclohenane, fused cyclohexane and lactone ring respectively (Cremer & Pople, 1975). In addition, the lactone ring bears in equatorial orientation a planar furan ring (r.m.s. deviation= 0.004 Å) which form an angle of 63.87 (13) o with the mean square plane (r.m.s. deviation Å) defined by the ten atoms of the two fused six-membered rings.

Experimental
General Experiment Procedures. Melting point was measured using a Fisher-Johns melting point apparatus. NMR spectra were recorded with a Bruker AV400 ( 1 H, 400 MHz; 13 C, 100 MHz) spectrometer using tetramethylsilane as an internal standard. Mass spectra were obtained from a Bruker micrOTOF mass spectrometer.
Plant Material. Fruits of X. moluccensis were collected from Surat Thani province, Thailand, in January 2010. Plant materials were identified by Royal Forest Department, Bangkok, Thailand.

Refinement
All H atoms were geometrically positioned and treated as riding atoms with distances C-H = 0.96 Å (CH3), 0.97 Å (CH2), 0.93 Å (CH), and U iso (H) = 1.20 U eq (C) for methylene and aromatic, 1.50 U eq (C) for methyl. The absolute structure could not be determined from the X-ray analysis, but it was known from earlier work on related compounds (e.g. Alvi et al., 1991, Yu et al., 2007and Li et al., 2009. 2388 Friedel pairs were therefore merged before the final refinement. The maximum residual density ( 0.68 eÅ 3 ) is larger than normally expected. However, the nearest atom to the corresponding minimum is O5 at 2.74 Å, which seems to indicate that de residual density can be associated to unmodeled disordered solvent molecules.

Figure 1
The molecular structure of the title compound with ellipsoids drawn at the 30% probability level.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.8749 (