The present invention relates to a compound of general formula (I) wherein R R and R are independently from each other hydrogen lower alkyl lower alkoxy cycloalkyl lower alkyl substituted by halogen or S lower alkyl or to a pharmaceutically acceptable acid addition salt to a racemic mixture or to its corresponding enantiomer and/or optical isomer thereof. It has been found that the compounds of general formula (I) are good inhibitors of the glycine transporter 1 (GlyT 1) and that they have a good selectivity to glycine transporter 2 (GlyT 2) inhibitors. The compounds may be used in the treatment of neurological and neuropsychiatric disorders.
