Patent ID: 8389697

Claim:
An anthracycline derivative of formula (IIc) Ant-L-(Z) m —X (IIc) wherein Ant has the structure: where the wavy line indicates the attachment to L; L is a linker selected from —CH 2 O—, —N(R) m (C 1 -C 12 alkylene)-X 1 , —N(R)—, —N(R) m (C 1 -C 12 alkylene)-, —N(R) m (C 2 -C 8 alkenylene)-, —N(R) m (C 2 -C 8 alkynylene)-, —N(R) m (CH 2 CH 2 O) n —, and the structures: where the wavy lines indicate the attachments to Ant and Z; and Z is an optional spacer selected from —CH 2 C(O)—, —CH 2 C(O)NR(C 1 -C 12 alkylene)-, and the structures: X is a reactive functional group selected from maleimide, thiol, amino, bromide, p-toluenesulfonate, iodide, hydroxyl, carboxyl, pyridyl disulfide, and N-hydroxysuccinimide; R is H, C 1 -C 12 alkyl, or C 6 -C 20 aryl; R 1 and R 2 are independently selected from an amino acid side chain; Z 1 is selected from —S—, —CH 2 C(O)—, —(CH 2 CH 2 O) n CH 2 C(O)—, —(CH 2 CH 2 O) n CH 2 — and —(C 1 -C 12 alkylene)-; m is 0 or 1; and n is 1 to 6.