Abstract: A new use of, and method of treatment using, a compound selected from the group consisting essentially of compounds of Formula I: ##STR1## 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 tetrahydronaphthyl;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.