Disclosed are compounds of formula I: ##STR1## or the pharmaceutically acceptable salts thereof wherein X is a carbonyl, sulfonyl, methylene, or methylene substituted with optionally substituted phenyl;Z is nitrogen or CH;Ar.sub.1 and Ar.sub.2 independently represent aryl groups; andY is hydrogen; orY and R.sub.1 or R.sub.2 together represent CH.sub.2 ; CH.sub.2 CH.sub.2 ; CH.sub.2 O; CH.sub.2 S forming a five or six membered ring and such ring may be optionally substituted with loweralkyl or phenyl; or pharmaceutically acceptable salts thereof, useful in the treatment of neoplastic diseases, and bacterial or fungal infections, and for preventing or decreasing the production of abnormally phosphorylated paired helical filament (PHF) epitopes associated with Alzheimer's Disease and, therefore for treating Alzheimer's Disease.