Method of Treating Colorectal Cancer

A method of treating refractory colorectal cancer in a mammal in need of such treatment comprising administering to said mammal a therapeutically effective amount of a compound of formula II

• wherein R is —(CH2)n— in which n is an integer from one to three;
• R1 is hydrogen, carboxyl, an alkyl group of from one to four carbon atoms, an alkyl group of from one to four carbon atoms substituted with an alkoxy group of from one to four carbon atoms, a cycloalkyl group of from three to six carbon atoms, a hydroxyalkyl group of from one to four carbon atoms, an alkoxy group of from one to four carbon atoms or benzyl;
• and
• R2 and R3 are negatively charged monodentate ligands which may be the same or different and are selected from the group consisting of chloro, bromo, iodo, hydroxo, nitrato, nitrito, acetato and dichloracetato or R2 and R3 taken together form a dinegatively charged bidentate ligand selected from the group consisting of sulfato, oxalato,
• in which R4 is hydrogen, hydroxyl, or an alkyl group of from one to four carbon atoms,
• in which o is an integer from one to three and
• and
• R5 and R6 are negatively charged monodentate ligands which may be the same or different and are selected from the group consisting of chloro, bromo, iodo, hydroxo, nitrato, nitrito, benzoato, 3,4,5-trihydroxybenzoato, 3,4,5-trimethoxtbenzoato, R7(CH2)p—CO2— wherein R, is selected from the group consisting of methyl, trifluoromethyl, CH2Cl, CH2Br, CH2F, CHCl2, CHBr2 and CHF2 and p is zero or an integer of one to five and R7(CH2)q—O— wherein R7 is defined above and q is zero or an integer of one to five.