Thermal Degradation of Glycosides, VI. Hydrothermolysis of Cardenolide and Flavonoid Glycosides
The hydrothermolysis of cardenolide and flavonoid glycosides is described. On heating with water or water/dioxane, cardenolide (1, 5, 11) and flavonoid glycosides (16, 20, 23, 27) are converted into their genuine aglycones and partially hydrolyzed products, together with saccharide components. Meanwhile, the glycosidic linkage of 2-deoxy sugar moieties in cardenolide glycosides is more readily cleaved than that of the common sugar moieties by means of hydrothermolysis. Therefore, hydrothermolysis of the uzarigenin triglycoside (13), bearing a 2-deoxy sugar moiety which is directly attached to the aglycone, leads to selective cleavage of the sugar—aglycone linkage. The hydrothermolyzed products have been isolated by chromatography and their structures elucidated by spectroscopic methods.