1 g of digitonin is dissolved in 10 mL of ethanol in a Schlenk tube under argon whereto 2.5 mL of conc. hydrochloric acid is added. The mixture is then refluxed for 2.5 h. After cooling in the refrigerator, the precipitate is filtered and washed with approximately 150 mL of water. The crude product is recrystallized with a minimum amount of dilute ethanol. It is dissolved in minimal amount of hot ethanol, water is added until turbidity occurs while boiling and then ethanol is added to clarify. The solution is then allowed to cool down in a refrigerator and the precipitated product is filtered off and dried in a vacuum at 80°C.
The pure product