8-[(3,3-Dimethyloxiran-2-yl)methoxymethyl]-11-hydroxy-2-isopropenyl-5-methyl-12-oxo-1,2,3,12-tetrahydropyrano[3,2-a]xanthen-1-yl acetate

The title compound, commonly known as 14-methoxytajixanthone-25-acetate, C28H30O8, was isolated from Emericella variecolor. The central xanthone core is approximately planar (r.m.s. deviation = 0.084 Å). The dihydropyran ring adopts a distorted half-chair conformation. The oxirane plane is oriented at an angle of 63.3 (2)° with respect to the phenol group. An intramolecular O—H⋯O hydrogen bond forms an S(6) ring. In the crystal, molecules are linked into a two-dimensional network parallel to the ab plane by weak intermolecular C—H⋯O hydrogen bonds.

The central xanthone core is approximately planar (r.m.s. deviation of 0.084 Å). The dihydropyran ring adopts a distorted half-chair conformation, with atoms C2 and C3 deviated 0.357 (3)Å and -0.315 (3) Å, respectively, out of the mean plane [r.m.s. deviation 0.214 Å]. The orientation of the isobutene side chain with respect to the acetate substitutent is indicated by the torsion angle O6-C1-C2-C21 of 166.1 (3)°, indicating a anti-periplanar conformation. The oxirane plane is inclined at an angle of 63.3 (2)° with respect to the phenol ring.
The crystal packing is stabilized by weak intermolecular C-H···O interactions (Fig.2).

Experimental
Seventy-five Erlenmeyer flasks (250 ml) containing malt extract (2 g) and water (100 ml per flask), were autoclaved twice at 121°C for 40 min. Pure culture of E.variecolor grown on PDA at room temperature for 7 days were cut into disks 8 mm in a diameter. Two disks were transferred under sterile conditions into each Erlenmeyer flask and then statically incubated for 6 weeks at room temperature. The fermentation broth was filtered through Whatman No.1 filter paper.
The mycelium (253 g wet weight) was extracted with methanol (500 ml × 10) to yield crude methanol extract that was a dark reddish solid (13.95 g). The dark reddish solid was re-extracted with ethyl acetate (500 ml × 10) to give 5.86 g of crude ethyl acetate extract. This extract was then separated by silica gel column chromatography (230-400 mesh, 100 g) and eluted with an n-hexane-ethyl acetate mixture with stepwise increasing polarity. A total of 600 fractions of 100 ml each were collected and combined on the basis of TLC profile. UV light and vanillin/H 2 SO 4 /EtOH reagent were used as detecting methods. The combined fraction (154 mg) contained the title compound as a main component. It was obtained from elution with hexane-EtOAc (80:20) and crystallized to give 14-methoxytajixanthone-25-acetate (75 mg). Suitable single crystals of the title compound were obtained by crystallization from a mixture of benzene/diethyl ether/chloroform.

supplementary materials sup-2 Refinement
The methyl group of the methoxy group is disordered over two orientations with occupancies of 0.700 (13) and 0.300 (13).
The C-O distances involving the disordered atoms were restrained to be equal and these atoms were subjected to a rigid bond restraint. The displacement parameters of atoms C16 and C17 were restrained to an approximate isotropic behaviour.
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å (aromatic), 0.97 Å (CH 2 ), 0.98 Å (CH 3 ) and O-H = 0.82 Å, and U iso (H) = 1.2U eq (C) and 1.5Ueq(O and C methyl ). In the absence of significant anomalous scattering effects, Friedel pairs were averaged. Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level. The dashed line indicates a hydrogen bond. Only the major disorder component is shown.