Synthesis and structural characterization of two epimers driven from 20(S)-protopanaxadiol

• Two epimers, 20S, 24R-epoxy dammarane-3β, 12β, 25-triol (3) and 20S, 24S-epoxy dammarane-3β, 12β, 25-triol (4) are prepared.
• The configuration of C-24 of 3 and 4 are R-form and S-form, respectively.
• 3 Generate a H-bonded tube with left-handed chiral channel.
• 4 Extend into 2D H-bonded network with right-handed and left-handed chiral channels.
• This study provides a facile way to synthesize and separate new types of chiral medicinal derivatives.

Two epimers, 20S,24R-epoxy dammarane-3β,12β,25-triol (3) and 20S,24S-epoxy dammarane-3β,12β,25-triol (4) were prepared from 20(S)-protopanaxadiol, which were confirmed by ESI-MS, NMR, and X-ray single-crystal diffraction. The results indicate the configuration of C-24 of 3 and 4 are R-form and S-form, respectively. 3 and 4 crystallize in a orthorhombic space group P2(1)2(1)2(1). Compound 3 have more complicated intramolecular hydrogen bonds than that of 4, which results in the weaker molecular polarity in 3. Crystal stacking displays that 3 generates a H-bonded tube with left-handed chiral channel, while 4 extends into two-dimensional network with right-handed and left-handed chiral channels in the solid state.