Cardiotonic steroids II: 3-deoxycardenolides and 3-deoxycardanolides

A series of compounds related to 3-deoxydigitoxigenin was prepared and assayed for inhibition of myocardial Na+,K+- adenosine triphosphatase. Although the relatively high activity of 3-deoxydigitoxin was confirmed, the corresponding 3beta,4beta-epoxide and a mixture of 2,3-olefins and 3,4-olefins were less active. 3-Deoxy compounds with variations at the 14-position and the butenolide ring were much less active than the corresponding 3beta-hydroxy analogs. Thus the activity of 3-deoxydigitoxigenin appears to be particularly susceptible to structural changes elsewhere in the molecule.