Summary. Structures for the genins of the ester glycosides of Marsdenia erecta are suggested. They are based on the behaviour in alkaline hydrolysis of these ester glycosides, their NMR. and mass spectra and ORD. data. All genins are derived from three acyl-free pregnane derivatives, i.e. drevogenin-P (l), 17B-marsdenin (3) and marsectohexol (7). The structure of 1 is known, 3 and 7 arc new compounds, i . e. 3 = 38, 88, llcr, 128, 14~-pentahydroxy-d6-pregnen-20-one and 7 = 3 8 , 88, lla, 128,14/?, 20&hexahydroxy-d6-pregnene.Formulae 13-17 were attributed to the acyl-genins A-1, A-2, A-3, A-4 and A-5, but only two of them were pure compounds, i. e . acyl-genin A-3 = 11,12-di-O-tiglyl-17~-marsdenin (15) and acyl-genin A-5 = 11,12-di-O-acetyl-marsectohexol (17). Acyl-genin A-1 is a mixture of the two esters 13af 13b derived from drevogenin-P, and similarly acyl-genin A-2 is a mixture of the esters 14a+ 14b derived from 178-marsdenin. The poorly characterised acyl-genin A-4 is most probably a mixture of the esters 16a+ 16b, also derived from 17@-marsdenin. [3]. Aus dem Gemisch der rohen Genine konnten neben ,&Sitosteryl-~-D-glucopyranosid und wenig Marsectohexol (7) 5 verschiedene krist. Praparate, die Acylgenine A1-A5, isoliert werden, von denen aber nur das Acylgenin A5 (17) rein war. A l (13) und A2 (14) bestanden jeweils aus zwei Komponenten, auch A3 (15) und A4 (16) waren kaum ganz einheitlich. -Nach alkalischer Verseifung der rohen Acylgenine konnten neben Sauren (Essigsaure, Tiglinsaure und Benzoesaure) die folgenden vier Desacylgenine in reinen Kristallen gefasst werden : 17-iso-Drevogenin-P (2), 17b-Marsdenin (3), Marsdenin (= 17~-Marsdenin) (5) und Marsectohexol (7). Diese Stoffe waren in kleinen Mengen schon vor der alkalischen Verseifung im rohen Geningemisch enthalten. Die Struktur des 17-iso-Drevogenins-P (2) ist bekannt [4]