THE CONSTITUENTS OF C₂₁-STEROIDS FROM DRFGEA SINENSIS VAR.CORRUGATA

Drevogenin Ⅰ, Ⅱ, two new aglycones, were isolated from Dregea sinensis var. corrugata(Asclepiadaceae). The mass spectrum suggests the presence of two isovaleryl groups.Alkaline hydrolysis of compound Ⅰ with 5% methanolic potassium hydroxide yielded deacyldrevogenin Ⅰa and isovaleric acid.The acid was esterified with methanol--surfuric acid to afford methyl-isovalerate. By GLC comparison with authentic sample,relative retention time was the same,¹H-NMR shift (δppm) and coupling constant were the same, too. On the basis of spectroscopic analysis and chemical reactions, given above the structure of aglyeone Ⅰ was established as C/D cis 5α-H,3β,8β,14β,17β tetrahydroxy- 12β-O-isovaleryl-20-O-isovalerylpregnane. MS moleculer weight 552 and elementary analysis were compatible with C₃₁H₃₂O₈.The structure of aglycone Ⅱ was established as C/D cis 5α-H,3β,14β,17β trihydroxy-12β-O-acetyl-20-O-benzoyl-pregnane,The mass spectrum suggests the presence of benzoyl and acetylgroups. Alkaline hydrolysis of Ⅱ with 5% methanolic potassium hydroxide yielded tomentogenin Ⅱa and an acetic acid. Partial alkaline hydrolysis of Ⅱ with 8% K₂CO₃--MeOH--H₂O afforbed a 12-hydroxy-20-O-benzoyl-pregnane.