Disclosed are compounds of formula I: ##STR00001## and the pharmaceutically acceptable salts thereof wherein the variables R.sub.N, R.sub.1, R.sub.2, R.sub.3, R.sub.P and R.sub.C are defined herein. These compounds are useful in treating Alzheimer's disease and other similar diseases. These compounds include inhibitors of the beta-secretase enzyme that are useful in the treatment of Alzheimer's disease and other diseases characterized by deposition of A beta peptide in a mammal. The compounds of the invention are useful in pharmaceutical compositions and methods of treatment to reduce A beta peptide formation.