[Synthesis and properties of digitoxigenin-3 beta-O-alpha-L-arabinofuranoside]

The synthesis of a cardenolide glycoside with a furanoide sugar component, digitoxigenin-3 beta-O-alpha-L-arabinofuranoside (4), is described for the first time. 4 was prepared by the reaction of digitoxigenin with 2,3,5-tri-O-benzoyl-alpha-L-arabinofuranosylchloride and Fétizon-reagent in benzene/dioxan followed by debenzoylation with ammonia in dry methanol. Compound 4 is cleaved by alpha-L-arabinofuranosidase (Aspergillus niger K1) into digitoxigenin and L-arabinose. Hydrolytic stability against methanolic HCl (0.1 mol/l) is relatively high. 4 X 10(-8) mol/l 4 gives a 50% inhibition of the Na,K-ATPase (pig heart muscle) and is 2.5 times more active at this receptor than the aglycon digitoxigenin.