The present invention relates to acompound of formula wherein L, Ar, R1, X and R are as defined in the specification; or a pharmaceutically suitable acid addition salt thereof, all racemic mixtures, all their corresponding enantiomers and/ or optical isomers.本發明係關於下式化合物其中L、Ar、R1、X及R係如說明書所定義;或其醫藥上適宜之酸加成鹽、所有外消旋混合物、所有其相應鏡像異構物及/或光學異構物。