[The constituents of C21-steroids from Dregea 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 (delta ppm) and coupling constant were the same, too. On the basis of spectroscopic analysis and chemical reactions, given above the structure of aglycone I was established as C/D cis 5 alpha-H, 3 beta, 8 beta, 14 beta, 17 beta tetrahydroxy-12 beta-O-isovalery1-20-O-isovalerylpregnane. MS molecular weight 552 and elementary analysis were compatible with C31H52O8. The structure of aglycone II was established as C/D cis 5 alpha-H, 3 beta, 14 beta, 17 beta trihydroxy-12 beta-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 absorbed a 12-hydroxy-20-O-benzoyl-pregnane.