Epothilone derivatives and their use as antitumor agents

A compound of formula I

• wherein
• T is O, NH or N(alkyl), wherein alkyl is alkyl;
• A is a radical of formula Ia
• which is bonded to the radical of the molecule according to formula I by one of the two carbon atoms marked with an arrow, and wherein
• X is S;
• O;
• NH;
• N(alk);
• wherein alk is alkyl, hydroxy-lower alkyl, unsubstituted or substituted amino-lower alkyl or carbamoyl-lower alkyl;
• N(ar), wherein ar is aryl;
• C(Rk*)═N, N═C(Rk*) or C(Rk*)═C(Rk**), wherein Rk* and Rk**, independently of one another, are H, alkyl, unsubstituted or substituted amino-lower alkyl, carbamoyl-lower alkyl, halogen-lower alkyl or hydroxy-lower alkyl;
• and
• Rk is H, alkyl, unsubstituted or substituted amino-lower alkyl, carbamoyl-lower alkyl, halogen-lower alkyl or hydroxy-lower alkyl;
• either Y is OH and Y* is hydrogen, or —Y and —Y* together form a bond (so that they form a double bond together with the adjoining bond connecting the two —Y and —Y* bearing carbon atoms);
• R is hydrogen, lower alkyl or halogen-lower alkyl;
• and Z is O, or —Z— is a bond between the two binding carbon atoms;
• or salts thereof.