PREGNANE DERIVATIVES OF SEEDS OF DREGEA ABYSSINICA (HOCHST) K SCHUM (ASCLEPIADACEAE) .2. STRUCTURAL DETERMINATIONS . GLYCOSIDES AND AGLYCONES .305.

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. Copyright © 1968 Verlag GmbH & Co. KGaA, Weinheim