Studies on the Steroidal Components of Domestic Plants. XVII. The Structure of Yonogenin, a New Steroidal Sapogenin from Dioscorea Tokoro MAKINO.

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Two new sapogenins, yonogenin and kogagenin, and tokorogenin were isolated from the epigeous part of Dioscorea Tokoro MAKINO. The structure of yonogenin was established to be 25D, 5β-spirostane-2β, 3α-diol (Va) by its degradation to samogenic acid (IIa) and by its conversion via Δ²-olefin (III) to samogenin (IVa), which was epimerized to original yonogenin (episamogenin). 25D, 5β-Spirostane-2α, 3β-diol (VIIa) was also prepared.