There is described compounds of Formula I, and salts, solvates and hydrates thereof: ##STR00001## wherein: R.sup.1, R.sup.2 and R.sup.3 are each independently selected from OH, C.sub.1-6alkyl, OC.sub.1-6alkyl, OC(O)C.sub.1-6alkyl, C(O)OC.sub.1-6alkyl, NH.sub.2, NH--C.sub.1-6alkyl, N(C.sub.1-6alkyl)(C.sub.1-6alkyl), C(O)NHC.sub.1-6alkyl, C(O)N(C.sub.1-6alkyl)(C.sub.1-6alkyl), SH, SC.sub.1-6alkyl, NO.sub.2, CF.sub.3, OCF.sub.3 and halogen; and Ar is an aromatic or heteroaromatic group chosen from benzene, naphthalene, quinoline, isoquinoline, indole, pyridine, pyrasine, pyrimidine, imidazole, furan and thiophene, unsubstituted or substituted with 1-4 substituents independently selected from OH, C.sub.1-6alkyl, C.sub.1-6alkoxy, C.sub.1-3alkylenedioxy, NH.sub.2, NH--C.sub.1-6alkyl, N(C.sub.1-6alkyl)(C.sub.1-6alkyl), SH, S--C.sub.1-6alkyl, NO.sub.2, CF.sub.3, OCF.sub.3 and halogen. The compounds of Formula I are useful: in therapeutic methods and compositions for modulating cell proliferation, in diagnostic assays and as research tools.