Synthesis and Biological Evaluation of 14 -Methoxy Digitalis Derivatives

The synthesis and biological evaluation of 14β-methoxy derivatives of digitoxigenin and of other digitalis-like compounds are reported. These compounds have a 14β-oxygen, which can be a hydrogen bonding acceptor, as is the case of 14β,15β-epoxide derivatives, but not a hydrogen bonding donor as is the case of 14β-hydroxy derivatives. All the new 14β-methoxy derivatives show a considerable reduced binding affinity on Na+,K+-ATPase when compared with the 14β-hydroxy analogues and also with the 14β,15β-epoxy derivatives. These results could mean that the digitalis receptor does not permit the presence of a bulky substituent in the 14β region, even of relatively small volume like the methyl group