The invention relates to compounds of formula (I) wherein R represents aryl orheteroaryl, X is oxygen, a carbonyl group, an oxime derivative of a carbonylgroup or an .alpha.,.szlig.-unsaturated carbonyl group, and the substituentsR1 to R6 have the meanings given in the specification, for use as medicaments,to novel compounds of formula (I), to methods of synthesis of such compounds,to pharmaceutical compositions containing compounds of formula (I), to the useof a compounds of formula (I) for the preparation of a pharmaceuticalcomposition for the treatment of neoplastic and autoimmune diseases, and tomethods of treatment of neoplastic and autoimmune diseases using suchcompounds of formula (I) or of pharmaceutical compositions containing same.
