The present invention relates to compounds of the Formula I ##STR00001## wherein R.sup.1, R.sup.3, R.sup.5, R.sup.7, X, Y and U are as defined. Compounds of the Formula I have activity inhibiting production of A.beta.-peptide. The invention also relates to pharmaceutical compositions and methods of treating diseases and disorders, for example, neurodegenerative and/or neurological disorders, e.g., Alzheimer's disease, in a mammal comprising compounds of the Formula I.