Disclosed are compounds of Formula (I) or prodrugs thereof; wherein: R1 is —CH2CF3 or —CH2CH2CF3; R2 is —CH2CF3, —CH2CH2CF3, or —CH2CH2CH2CF3; R3 is H or —CH3; each Ra is independently F, Cl, —CN, —OCH3, and/or —NHCH2CH2OCH3; and z is zero, 1, or 2. Also disclosed are methods of using such compounds to inhibit the Notch receptor, and pharmaceutical compositions comprising such compounds. These compounds are useful in treating, preventing, or slowing the progression of diseases or disorders in a variety of therapeutic areas, such as cancer.