Three New Polyoxypregnane Glycosides from Marsdenia tenacissima

Three new polyoxypregnane glycosides, marsdenosides I–K ( 1 – 3 ), were isolated from the stem of Marsdenia tenacissima. The structures were elucidated on the basis of in‐depth spectroscopic analyses, and by means of chemical evidence. Marsdenoside I ( =  (3 β ,5 α ,11 α ,12 β ,14 β ,17 α ,20 R )‐3‐[(2,6‐dideoxy‐4‐O‐(6‐deoxy‐3‐O‐methyl‐ β ‐ D ‐allopyranosyl)‐3‐O‐methyl‐ β ‐ D ‐arabino‐hexopyranosyl)oxy]‐8,20 : 11,20‐diepoxypregnane‐12,14‐diol; 1 ) is the first C 21 steroidal glycoside with a rigid cage. Also, the isolation of 1 demonstrated that tenacigenin A ( 1a ) is a true natural product as well, rather than an artifact.