Two new β-hydroxy amino acid-coupled secoiridoids from the flower buds of Lonicera japonica: Isolation, structure elucidation, semisynthesis, and biological activities
Two new β-hydroxy amino acid-coupled secoiridoids, named serinosecologanin (1) and threoninosecologanin (2), were isolated from an aqueous extract of the flower buds of Lonicera japonica. Their uncommon structures including absolute configurations were de
Transformation of naturally-occurring 1,9-trans-9,5-cis sweroside to all trans sweroside during acetylation of sweroside aglycone
From the rootstock of Scabiosa columbaria L. loganin and sweroside were isolated. Sweroside showed moderate antibacterial activity. Pure sweroside was converted to the sweroside aglycone l-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.