The glycosides of Marsdenia erecta R. Br. I. Isolation, glycoside and aglycone. 325

Dried leaves of Marsdenia erecta R. Br. gave over 6% of a crude glycoside mixture, the main portion of which consisted of weakly polar material, soluble in ether or chloroform. By mild acid hydrolysis it yielded crude sugars and aglycones. The following four crist. sugars were isolated: D -cymarose, D -oleandrose and two bioses: pachybiose and marsectobiose (C₁₄H₂₄O₈, new). By PC. and TLC. the presence of digitoxose, canarose, thevetose and 3-O-methyl-6-deoxyallose could be demonstrated. The crude acyl-genin mixture contained β-sitosteryl-β-D -glucopyranoside and three highly hydroxylated pregnane derivatives: drevogenin-P, 17 β-marsdenin (C₂₁H₃₂O₆, new) and marsectohexol (C₂₁H₃₄O₆, new), all partly esterified with acetic, tiglic and benzoic acid. Five crist. acyl-genins (A1–A5) were isolated by chromatography, but most of them still were mixtures. After alkaline hydrolysis of the crude acyl-genins 6 acyl-free compounds were obtained. 4 of them were identical with the above mentioned substances, the other two: 17-iso-drevogenin-P and marsdenin (17 α-marsdenin) are formed from drevogenin-P and 17 β-marsdenin by isomerisation.