Die Pregnanderivate der Samen von Dregea abyssinica (H OCHST .) K. Schum. ( Asclepiadaceae ) . II. Strukturbestimmungen Glykoside und Aglykone, 305. Mitteilung

The total or partial structure determinations of some new components from Dregea abyssinica are reported. The four drebyssogenins (F, G, J and H) are esters of the drevogenins P ( 7 ) and D( 9 ) and have the following structures: Drebyssogenin F ( 5 ) = 11‐O‐acetyl‐12‐O‐(α‐hydroxyisovaleryl)‐drevogenin P, drebyssogenin G ( 14 ) = 11‐O‐acetyl‐12‐O‐isovaleryl‐drevogenin D, drebyssogenin J ( 15 ) = 11, 12‐di‐O‐acetyl‐drevogenin D. Drebyssogenin K is a mixture of K1 ( 16 ) and K2 ( 17 ), the mono‐O‐tiglyl and mono‐O‐isovaleryl derivatives of drevogenin D respectively, with as yet undetermined position of the acyl residues. The drebyssosides 1, 2 and 3 are glycosides of trisaccharides. Drebyssoside 1 ( 2 ) is pachybiosyl‐cymarosyl‐drevogenin A, drebyssoside 2 ( 3 ) asclepobiosyl‐cymarosyl‐drevogenin A and drebyssoside 3 ( 6 ) pachybiosyl‐cymarosyl‐drebyssogenin F. Drebyssoside 4 is a mixture of at least two components and contains the same aglycones and the same sugar units as the drebyssosides 1 and 3, but is different from them. The full structure of the two sugars (drebyssobiose ( 25 ) and sugar T ( 24 )) has not been determined; it is only shown that both are disaccharides which contain 3‐O‐methyl‐6‐deoxy‐allose linked to a 2‐deoxyhexose.