Interconversion of hederagenin and gypsogenin and accessing 4-epi-hedragonic acid.

• Hederagenin and gypsogenin have been isolated from plant material. • Both compounds can be interconverted in good yields. • Oxidation of gypsogenin followed by decarboxylation led to 4- epi -hedragonic acid. Gypsogenin (1) and hederagenin (2) were isolated by extracting the powdered roots of Saponaria officinalis and the pericarp of Sapindus saponaria , respectively. While the gypsophila derived saponin can be obtained easily and in large quantities as a technical product, the plant material from Sapindus saponaria is difficult to obtain in Europe and the North-Americas, whereas in Latin America it is readily available (unlike the gypsophila saponin). In order to achieve a better accessibility of both aglycones, gypsogenin (1) and hederagenin (2), a simple synthesis for their interconversion was developed. Modification of the reaction conditions led to the first synthesis of 4- epi -hedragonic acid (3). [ABSTRACT FROM AUTHOR]