A method of treatment using a compound of Formula I: ##STR00001## wherein: R.sub.1 is hydrogen, lower alkanoyl of up to 6 carbon atoms or aroyl selected from benzoyl and naphthoyl; R.sub.2 is hydrogen, lower alkyl of up to 6 carbon atoms or arylalkyl selected from benzyl, phenylethyl and phenylpropyl; R.sub.3 is hydrogen or lower alkyl of up to 6 carbon atoms; R.sub.4 is hydrogen or lower alkyl of up to 6 carbon atoms, or when X is oxygen, R.sub.4 together with R.sub.5 can represent --CH.sub.2--O--; X is a valency bond, --CH.sub.2, oxygen or sulfur; Ar is selected from phenyl, naphthyl, indanyl and tetrahydronapthyl; R.sub.5 and R.sub.6 are individually selected from hydrogen, fluorine, chlorine, bromine, hydroxyl, lower alkyl of up to 6 carbon atoms, a --CONH.sub.2-- group, lower alkoxy of up to 6 carbon atoms, benzyloxy, lower alkylthio of up to 6 carbon atoms, lower alkysulphinyl of up to 6 carbon atoms and lower alkylsulphonyl of up to 6 carbon atoms; or R.sub.5 and R.sub.6 together represent methylenedioxy; or a pharmaceutically acceptable salt thereof, alone or in conjunction with one or more other therapeutic agents, said agents being selected from the group consisting of ACE inhibitors, diuretics, and digoxin for decreasing mortality resulting from congestive heart failure (CHF) in mammals, particularly humans.