The present invention relates to a compound of general formula (I) wherein X is -O- or -CH2-； X' is -O- or -CH2-； with the proviso that one of X or X' is always -O- and the other is -CH2-.It has been found that the compounds of general formula (I) are good inhibitors of the glycine transporter 1 (GIyT-1) and therefore they may be used for the treatment of schizophrenia, psychoses and other neurological conditions, including pain.
