The invention is concerned with partially new compounds of the general formula ##STR1## wherein R.sup.1 is a hydrogen atom or an alkyl group with up to four carbon atoms and R.sup.2 a substituted phenyl radical and the pharmacologically acceptable salts thereof.The compounds can be prepared according to known procedures and show surprisingly a cardiovascular efficacy. They are capable of decompensating cardiac insufficiencies to a large extent. In addition to the new compounds, claim is also made for pharmaceutical compositions which contain compounds according to the general formula and their application for controlling cardiac and vascular diseases.