Compounds formula (I): ##STR1## in which: R.sup.1 represents a hydrogen atom, an alkyl group, a substituted alkyl group, a C.sub.2 -C.sub.6 alkenyl group, an aryl group, a substituted aryl group or an alkoxycarbonyl group wherein the alkoxy part has from 1 to 6 carbon atoms; R.sup.2 represents a hydrogen atom, a C.sub.1 -C.sub.6 alkyl group or a C.sub.3 or C.sub.4 alkenyl group; R.sup.3 represents a hydrogen atom or a C.sub.1 -C.sub.6 alkyl group; R.sup.4 represents a hydroxy group, a C.sub.1 -C.sub.21 aliphatic acyloxy group or a carbocyclic aryl carboxylic acyloxy group; R.sup.5 represents a C.sub.1 -C.sub.12 alkyl group, a C.sub.1 -C.sub.6 alkoxy group, a hydroxy group, a C.sub.1 -C.sub.7 aliphatic acyloxy group or a carbocyclic aryl carboxylic acyloxy group; R.sup.6 represents a hydrogen atom, a C.sub.1 -C.sub.6 alkyl group or a C.sub.1 -C.sub.6 alkoxy group; and n is 0, 1, or 2; and pharmaceutically acceptable salts thereof are valuable in the treatment of circulatory disorders and allergies.