Compounds of Formula (I),
##STR1##
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, T, W, X, Y
and Z are as defined herein are provided, together with pharmaceutically
acceptable salt, hydrates and/or prodrugs thereof. Methods of using these
compounds for inhibiting beta amyloid production and for treatment of
Alzheimer's Disease and Down's syndrome are described
