Two New C21 Steroids from Marsdenia tenacissima

Two new C21 steroids were isolated from the CHCl3 extract of the stem of Marsdenia tenacissima. On the basis of spectroscopic analysis and chemical methods, their structures were elucidated as 17β-tenacigenin B (2) and 3-O-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandropyranosyl-tenacigenin C (3). The structure of the known aglycon tenacigenin C was revised as 5α, 9α, 17β-pregnane-3β, 8β, 11α, 12β, 14β-pentanol-20-one. Compound 3 is the fust reported glycoside of tenacigenin C.