ynthesis and Biological Evaluation of 2-Hydroxy Derivatives of Digitoxigenin and 3-Epidigitoxigenin

Digitalis cardiac glycosides are well known drugs clinically used for treatment of congestive heart failure.1 Their action is mainly due to inhibition of Na+,K+-ATPase, an enzyme located in the cell membrane and promoting the outward transport of Na+ and the inward transport of K+.2 The most potent inhibitors of Na+,K+-ATPase are cardenolides such as digoxin, digitoxin, digitoxigenin and gomphoside (Figure 1). The first three compounds have some common features, typical of digitalis: 17b-unsaturated lactone; 14b-hydroxy; A/B and C/D cis ring junctions; 3b-hydroxy or 3b-glycosyl linkage with digitoxose. A quite different molecule is gomphoside, an A/B trans cardiac glycoside from Asclepias fruticosa RBr,3 in which the aglycone (gomphogenin) is linked to a 4,6-dideoxyhexosulose trhough its 2a- and 3b-hydroxy groups.