20-O-β-d-Xylopyranosyl(1→6)-β-d-glucopyranosyl-20(S)-protopanaxadiol methanol solvate

The title compound, C41H70O12·CH4O, was prepared by microbial transformation. Within the steroid skeleton of the molecule, three six-membered rings exhibit a chair conformation, while the five -membered ring adopts an envelope conformation. The two pyranosyl rings also adopt chair conformations. The molecules are held together by an extensive O—H⋯O hydrogen-bonding network.

The title compound, C 41 H 70 O 12 ÁCH 4 O, was prepared by microbial transformation. Within the steroid skeleton of the molecule, three six-membered rings exhibit a chair conformation, while the five -membered ring adopts an envelope conformation. The two pyranosyl rings also adopt chair conformations. The molecules are held together by an extensive O-HÁ Á ÁO hydrogen-bonding network.

20-O-β-D-Xylopyranosyl(1→6)-β-D-glucopyranosyl-20(S)-protopanaxadiol methanol solvate
Xing-Wei Li, Wei Zhou, Qin Yan and Pei Zhou S1. Comment 20-O-β-D-xylopyranosyl(1→6)-β-D-glucopyranosyl-20(S)-protopanaxadiol is a kind of rare gensenoside, found existing in notoginseng. In recent studies, the compound has been related to an anticancer agent. It is believed to have activities including: cytotoxicity to and partial reversal of multidrug resistance of human tumor cells (He et al., 2005). Besides that, the compound may be an important precurosor metabolite of Compound K, which is also a potential anticancer agent, during the process of microbial transformation of gisenoside Rb 3 (Hu et al., 2007). In this article, the crystal structure is reported.
The structure mainly consists of a protopanaxadiol moiety with a disaccharide group. The bond distances and angels are normal. The C24?C25 of 1.313 (5) Å shows a typical double bound. Within the steroid skeleton of the molecule, three six membered rings all display the chair conformation, while a five membered ring displays an envelope conformation. Two pyranosyl rings are also exist in chair conformation. Extensive O-H···O hydrogen bonding occurs in the crystal structure (Table 1), which helps to stabilize the crystal structure.

S2. Experimental
The Fermentation broth of ginsenoside Rb 3 (300 mg) was centrifuged and the precipitation was extracted with EtOH for 24 h. Removal of the EtOH from the extract under reduced pressure gave crude extract. And the extract was subjected to silica gel column chromatography, eluting with HCCl 3 :CH 3 OH (10:1→7:3→5:1) to afford 12 fractions. Recrystallizing of fractions 8~10 yielded ginsenoside Rb 3 100 mg. Solvent loss technique was then employed for the growth of crystals at room temperature, using methanol as the solvent.

S3. Refinement
Hydroxyl H atoms were located in a Fourier map and refined as riding in as-found relative positions with U iso (H) = 1.2U eq (O). Other H atoms were placed in geometrically calculated positions with C-H = 0.93-0.98 Å and constrained to ride on their parental atoms with U iso (H) = 1.2U eq (C). Torsonal angles for methyl groups were refined to fit the electron density. In absence of significant anomalous scattering, Friedel pairs were meged.  The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.  The packing of (I), viewed down the c axis. H atoms not involved in hydrogen bonding have been omitted.

Data collection
Bruker SMART APEX CCD area-detector diffractometer Radiation source: fine-focus sealed tube Graphite monochromator φ and ω scans 25549 measured reflections 5269 independent reflections 3467 reflections with I > 2σ(I)

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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. Symmetry codes: (i) −x, y−1/2, −z+1/2; (ii) x, y−1, z; (iii) x−1/2, −y+3/2, −z; (iv) x−1, y, z; (v) x, y+1, z; (vi) x−1/2, −y+5/2, −z; (vii) x+1, y, z.