Transformation of naturally-occurring 1,9-trans-9,5-cis sweroside to all trans sweroside during acetylation of sweroside aglycone.

M M Horn, S E Drewes, N J Brown, O Q Munro, J J Meyer, A D Mathekga

Index: Phytochemistry 57(1) , 51-6, (2001)

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Abstract

From the rootstock of Scabiosa columbria L. loganin and sweroside were isolated. Sweroside showed moderate antibacterial activity. Pure sweroside was converted to the sweroside aglycone 1-acetoxy derivative (DABCO/Ac2O) after hydrolysis of the glucose unit. X-ray crystallography of the monoacetate showed unambiguously that it had been transformed to a new seco-iridoid having the novel trans diaxial configuration for the protons on C-1, C-9 and C-5. The mechanism for the rearrangement is discussed.