Compound (III), mp 247-253°C, [α]D -5.9 ± 2 ° (c 1.0; chloroform-methanol). The elementary analysis corresponded to the figures calculated for the composition C41H64O23. Since the initial digitoxin had the same composition, we assume that (III) was isodigitoxin, i.e., 14β,21-epoxycardenolide. An independent isomerization of digitoxin with the aid of KOH led to an identical compound. Thus, the saponification of acylcardenolides by ammonia is accompanied by the formation of by-products -- 14β,21-epoxycardenolides and their lactam analogues. Both these types of cardiotonic derivatives have low activities [1, 2]. We consider that the method of deacetylating cardiac glycosides with ammonia is unsuitable in industrial practice since it greatly complicated the purification of the desired substances and lowers the yield.