Abstract: Novel therapeutically active compounds of the formula ##STR1## wherein Z.sup.i, being Z.sup.1, Z.sup.2 or Z.sup.3, is the same or different and selected among OH, OR.sup.1, NH.sub.2, NR.sub.2.sup.4, NHR.sup.4, SH, SR.sup.4 and OR.sup.4 wherein R.sup.1 is a formyl group, an acyl group, an alkoxycarbonyl group or a mono- or dialkylcarbamoyl group and R.sup.4 is a lower alkyl group,R.sup.2 is a hydrogen, a halogen, a lower alkyl or a lower trifluoroalkyl group,R.sup.3 is a hydrogen atom, a lower alkyl group, an alkenyl group, an alkynyl group or a phenyl group, which phenyl group could optionally be substituted by one or more of fluoro, chloro, bromo, trifluoromethyl, methyl, ethyl, methoxy or ethoxy in the ortho, meta or para positions, or optionally substituted by methylenedioxy, provided that at least one of Z.sup.1, Z.sup.2 and Z.sup.3 is a group OR.sup.4 and further provided that when Z.sup.2 is OH or NH.sub.2, Z.sup.1 is NR.sub.2.sup.4, NHR.sup.4, SH, SR.sup.4 or OR.sup.