Disclosed are novel gamma secretase inhibitors of the formula (I): or a pharmaceutically acceptable salt, solvate, or ester thereof, wherein L1, n, X, Ar, Y, Z, Q, and Q1 are as defined herein. Also disclosed are methods for inhibiting gamma secretase, methods for treating Alzheimer's disease, methods of treating one or more neurodegenerative diseases, and methods of inhibiting the deposition of amyloid protein (e.g., amyloid beta protein) in, on or around neurological tissue (e.g., the brain) using the compounds of formula 1.0.