The invention relates to a compound of the formula ##STR1## wherein R.sub.1 is a linear or branched alkyl of 4 to 20 carbon atoms;R.sub.2 is hydrogen, halogen, alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms or a bivalent radical --CH.dbd.CH--CH.dbd.CH-- or --(CH.sub.2).sub.n --, where n is an integer from 3 to 5, inclusive, and the free bonds of said bivalent radical are attached to adjacent carbon atoms of the phenyl ring; andR.sub.3 is hydrogen or alkyl of 1 to 3 carbon atoms;R.sub.4 is alkyl of 1 to 3 carbon atoms; orR.sub.3 and R.sub.4, together with each other, are --(CH.sub.2).sub.p --, where p is an integer from 4 to 6, inclusive,or a non-toxic, pharmacologically acceptable acid addition salt thereof. The compounds of formula I are useful for treatment and prophylaxis of diseases of the coronaries, for the treatment of hypertension, and for treatment of cardiac arrhythmia, particularly tachycardia.