Certain 5-nitrothiazolylimidazolidine compounds

Compounds of formula I, ##STR13## in which R.sub.1 is hydrogen, lower alkyl or phenyl, R.sub.2 is hydrogen, lower alkyl or alkoxy, trifluoromethyl, the group --CH.dbd.CH--COOH or a group --N(R.sub.3)(R.sub.4), in which R.sub.3 and P.sub.4, which may be the same or different, each signifies hydrogen or lower alkyl, and

• X is oxygen, sulphur or imino, provided that when R.sub.2 is lower alkyl or --CH.dbd.CH--COOH, then X is oxygen,
• or a chemotherapeutically acceptable acid addition salt thereof.