US Patent 7557215 Anthraquinone compounds as anti cancer compounds

Anthraquinone compounds of the general formula (I) or a salt thereof (Formula I) in which R1 to R4 are each selected from the group consisting of H, C1-4 alkyl, X1, —NHR0N (R5)2 in which R0 is a C1-12 alkanediyl and each R5 is H or optionally substituted C1-4 alkyl, and a group of formula (II) in which at least one of R6, R7 and R8 is selected from X2, and X2 substituted C1-4 alkyl and any others are H or C1-4 alkyl; R9 is selected from H, C1-4 alkyl, X2 and X2 substituted C1-4 alkyl; m is 0 or 1; n is 1 or 2; X1 is a halogen atom, a hydroxyl group, a C1-6 alkoxyl group, an aryloxy group or an acyloxy group; and X2 is a halogen atom, a hydroxyl group, a C1-6 alkoxyl group, an aryloxy group or an acyloxy group; provided that at least one of R1 to R4 is a group of formula (II). The N-oxides are useful prodrugs which are selectively bioreduced in hypoxic tumours to the corresponding cyclic amine derivatives. The amine compounds are cytotoxic and may be used as alkylating agents having topoisomerase II inhibiting activities in cancer therapy.