The invention relates to a compound of formula I wherein Ar1, Ar2, R1, R2, R3, R4, n, o, p, and q are as defined herein and to a pharmaceutically active salt thereof, including all stereoisomeric forms, individual diastereoisomers and enantiomers of the compound of formula (I) as well as racemic and non-racemic mixtures thereof. The 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).