Disclosed are compounds of Formula (I) and/or salts thereof: wherein R1 is —CH2CH2CF3; R2 is —CH2CH2CF3 or —CH2CH2CH2CF3; R3 is H, —CH3, or Rx; R4 is H or Ry; Ring A is phenyl or pyridinyl; and Rx, Ry, Ra, Rb, y, and z are defined herein. 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; or as prodrugs of such compounds.