Die Glykoside von Vincetoxicum hirundinaria, MEDIKUS. 2. Mitteilung: Hydrierungen und Umlagerungen der Genine sowie Massenspektren

The course of hydrogenation of hirundigenin (7) (C21H30O5), either in acetic acid or ethanol, is strongly influenced by the solvent used. In acetic acid tow moles of hydrogen were taken up very quickly under saturation of the double bond and hydrogenolysis of the hydroxyl group. In ethanol, first the cyclohemiketal ring was slowly opened to a triol, and subsequently the double bond was saturated very slowly. In the case of anhydrohirundigenin (11) hydrogenation of the δ5-double bond occurred rapidly in acetic acid. Subsequently, the δ8, 14-ethylenic linkage was also slowly hydrogenated under formation of two stereomeric trans-derivatives. Vincetogenin consumed two moles of hydrogen in acetic acid, and this resulted in the formation of two isomers as well. Hirundigenin and anhydrohirundigenin are stable toward alkaline hydrolysis, but do rearrange in the presence of acids. One of the isomerisation products of dihydro-anhydrohirundigenin has been isolated in pure form.