The present invention relates to a compound of formula I wherein Ar, R1, R2, R3, n, and o are as defined herein or to a pharmaceutically active salt, a racemic mixture, an enantiomer, an optical isomer or a tautomeric form thereof. The present compounds are high potential NK-3 receptor antagonists for the treatment of depression, pain, psychosis, Parkinson's disease, schizophrenia, anxiety and attention deficit hyperactivity disorder (ADHD).