the present invention relates to compounds of the formula wherein r 3 , r 5 , r 7 , u , x , y and z are as defined . compounds of the formula i have activity inhibiting production of aβ - peptide . this invention also relates to pharmaceutical compositions and methods of treating diseases , for example , neurodegenerative diseases , e . g ., alzheimer &# 39 ; s disease , in a mammal comprising compounds of the formula i .