Conjugates anthracycline, process for their preparation and their use as antitumor compounds

An anthracycline derivative of Formula (IIc) Ant-L- (Z) m X (IIc) wherein Ant is selected from the structure: ** ** Formula wherein the wavy line indicates the attachment to L; L is a linker selected from -N (R) -, -N (R) m (C1-C12) -, -N (R) m (C2-C8) -, - N (R) m (C2 alkynylene C8) -, -N (R) m (CH2CH2O) n-, and the structure: ** ** Formula wherein wavy lines indicate the attachments to Ant and Z; and Z is an optional spacer selected from -CH2C (O) -, -CH2C (O) NR (C1-C12) -, and the structures: ** ** Formula X is a functional group selected from maleimide reagent, thiol, amino, bromide, p-toluenesulfonate, iodide, hydroxyl, carboxyl, pyridyl disulfide, and N-hydroxysuccinimide; R is H, C1-C12 alkyl or C6-C20 aryl; R1 and R2 are independently selected from amino acid side chain; Z1 is selected from - (C1-C12 alkylene) -, - (C2-C8) -, - (C2-C8 alkynylene) - and - (CH2CH2O) n-; m is 0 or 1; n is 1 to 6; or wherein the anthracycline derivative is selected from the structures: ** ** Formula wherein Z is C1-C12, ** ** Formula