2123The present invention relates to a compound of general formula I A or I B wherein X is a bond or a CH group R R and R are independently from each other hydrogen lower alkoxy 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 formulas I A and I B are good inhibitors of the glycine transporter 1 (GlyT 1) and that they have a good selectivity to glycine transporter 2 (GlyT 2) inhibitors suitable in the treatment of neurological and neuropsychiatric disorders.
