Compounds of the general formulae ##STR1## in which R.sub.1 represents a straight or branched, optionally substituted alkyl, alkenyl or alkynyl radical; R.sub.2 stands for an optionally substituted phenyl radical; Y stands for oxygen, sulphur or a methylene radical; X stands for O or H.sub.2 ; their salts and esters and methods for their preparation. The compounds of the invention possess an outstanding diuretic and saluretic activity with a very low excretion of potassium ions and a low toxicity.