We describe compounds of the following general formula (I): wherein X is fluorine or chlorine; Y is oxygen, sulfur, or an amino group; R is an amino, hydroxyl, sulfonamide, or carboxamide group or an N-monomethyl or N-dimethyl analog thereof; m is an integer from 2 to 6, and n is an integer from 0 to 2. The compounds may be used for treating certain cancers and autoimmune diseases.