Stereochemical Survey of Digitoxin Monosaccharides

Abstract

A stereochemically diverse array of monosaccharide analogues of the trisaccharide based cardiac glycoside natural product digitoxin has been synthesized using a de novo asymmetric approach. The analogues were tested for cytotoxicity against the NCI panel of 60 human cancer cell lines and in more detail against non-small cell human lung cancer cells (NCI-H460). The results were compared with digitoxin and its aglycone digitoxigenin. Three novel digitoxin monosaccharide analogues with β-d-digitoxose, α-l-rhamnose, and α-l-amicetose sugar moieties showed excellent selectivity and activity. Further investigation revealed that digitoxin α-l-rhamnose and α-l-amicetose analogues displayed similar anti-proliferation effects, but with at least 5-fold greater potency in apoptosis induction than digitoxin against NCI-H460. This study demonstrates the ability to improve the digitoxin anti-cancer activity by modification of the stereochemistry and substitution of the carbohydrate moiety of this known cardiac drug.