Abstract
In order to obtain the more potent cardiotonic drug digitoxigenin 3-suberoylpeptides whose peptide moieties are derived from the partial structure of kinin, have been synthesized. Some of the desired compounds were prepared from digitoxigenin 3-suberoyl-p-nitrophenol (I) by direct condensation with the pertinent di- or tri-peptide. As for the steroidal peptides having the readily unavailable amino acid sequence the stepwise method involving the repeated p-nitrophenyl ester formation was carried out. The condensation reaction of p-nitrophenyl ester with amino acid or peptide was considerably improved in respect with the yield, when the amino group was activated by leading to the carbamate.
