The present invention relates to a compound of formula I
wherein R
1
, R
2
, and Ar are as defined herein or to a pharmaceutically acceptable acid addition salt, to a racemic mixture, or to its corresponding enantiomer and/or optical isomer thereof. These compounds and their pharmaceutical compositions are useful in the treatment of neurological and neuropsychiatric disorders.
3-Amido-3-aryl-piperidines were discovered as a novel structural class of GlyT1 inhibitors. The structure–activity relationship, which was developed, led to the identification of highly potent compounds exhibiting excellent selectivity against the GlyT2 isoform, drug-like properties, and in vivo activity after oral administration.