New Acylated Preatroxigenin Saponins from Atroxima congolana

Abstract Eight new acylated preatroxigenin saponins 1 – 8 were isolated as four inseparable mixtures of the trans‐ and cis‐ 4‐methoxycinnamoyl derivatives, atroximasaponins A 1 /A 2 ( 1 / 2 ), B 1 /B 2 ( 3 / 4 ), C 1 /C 2 ( 5 / 6 ) and D 1 /D 2 ( 7 / 8 ) from the roots of Atroxima congolana. These compounds are the first examples of triterpene saponins containing preatroxigenin (=(2 β ,3 β ,4 α ,22 β )‐2,3,22,27‐tetrahydroxyolean‐12‐ene‐23,28‐dioic acid as aglycone. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR studies and FAB‐MS as 3‐ O ( β‐ D ‐glucopyranosyl)preatroxigenin 28‐{ O ‐ β ‐ D ‐xylopyranosyl‐(1→4)‐ O ‐ α ‐ L ‐rhamnopyranosyl‐(1→2)‐ O ‐[ O ‐ β ‐ D ‐glucopyranosyl‐(1→3)‐ β ‐ D ‐glucopyranosyl‐(1→3)]‐4‐ O‐ ( trans ‐4‐methoxycinnamoyl)‐ β ‐ D ‐fucopyranoyl} ester ( 1 ) and its cis‐ isomer 2 , 3‐ O ‐( β ‐ D ‐glucopyranosyl)preatroxigenin 28‐{ O ‐ β ‐ D ‐xylopyranosyl‐(1→4)‐ O ‐ α ‐ L ‐rhamnopyranosyl‐(1→ 2)‐ O ‐[ O ‐6‐ O ‐acetyl‐ β ‐ D ‐glucopyranosyl‐(1→3)‐ β ‐ D ‐glucopyranosyl‐(1→3)]‐4‐ O‐ ( trans ‐ 4‐methoxycinnamoyl)‐ β ‐ D ‐fucopyranosyl} ester ( 3 ) and its cis‐ isomer 4 , 3‐ O ‐( β ‐ D ‐glucopyranosyl)preatroxigenin 28‐{ O ‐ β ‐ D ‐xylopyranosyl‐(1→4)‐ O ‐[ β ‐ D ‐apiofuranosyl‐(1→3)]‐ O ‐ α ‐ L ‐rhamnopyranosyl‐(1→2)‐ O ‐[ O ‐6‐ O ‐acetyl‐ β ‐ D ‐glucopyranosyl‐(1→3)‐ β ‐ D ‐glucopyranosyl‐(1→3)]‐4‐ O‐ ( trans ‐4‐methoxycinnamoyl)‐ β ‐ D ‐fucopyranoyl} ester ( 5 ) and its cis ‐isomer 6 , 3‐ O ‐( β ‐ D ‐glucopyranosyl)preatroxigenin 28‐{ O ‐ β ‐ D ‐xylopyranosyl‐(1→4)‐ O ‐[ β ‐ D ‐apiofuranosyl‐(1→3)]‐ O ‐ α ‐ L ‐rhamnopyranosyl‐(1→2)‐ O ‐[ O ‐ β ‐ D ‐xylopyranosyl‐(1→3)‐ β ‐ D ‐glucopyranosyl‐(1→3)]‐4‐ O ‐( trans ‐4‐methoxycinnamoyl)‐ β ‐ D ‐fucopyranosyl ester ( 7 ) and its cis‐ isomer 8 .