The invention relates to compounds of formula (I), wherein R1 is hydrogen, lower alkyl or cycloalkyl； R2 is hydrogen or R1 and R 2 may form together with the N and C atom to which they are attached a pyrrolidine ring optionally substituted by one or two F-atoms or by hydroxy, or may form an azetidine or a piperazine ring； R3 is hydrogen, lower alkyl, lower alkyl substituted by hydroxy, -(CH2)2C(O)NH2, benzyl, phenyl, -CH2-five membered aromatic heterocyclic group, CH2-indolyl, -CH2-cycloalkyl, cycloalkyl or -(CH2)2-S-lower alkyl； R3' is hydrogen or lower alkyl； or X is -C(0)-CHR4-CHR4 -C(0)-NH-CH2- R4/R4 are hydrogen or one of R4 or R4 is amino: o is 0 or 1； or to pharmaceutically acceptable acid addition salt, to a racemic mixture or to its corresponding enantiomer and/or optical isomers thereof. It has been found that the present compounds are oxytocin receptor agonists for the treatment of autism, stress, including post traumatic stress disorder, anxiety, including anxiety disorders and depression, schizophrenia, psychiatric disorders and memory loss, alcohol withdrawel, drug addiction and for the treatment of Prader-Willi Syndrom.La invención se refiere a compuestos de fórmula (I) en donde R1es hidrógeno, alquilo inferior o cicloalquilo； R2 es hidrógeno o R1 y R2 pueden formar junto con el átomo de N y C al que están unidos un anillo de pirrolidina opcionalmente sustituido con uno o dos átomos de F o con hidroxi, o puede formar una azetidina o un anillo de piperazina； R3 es hidrógeno, alquilo inferior, alquilo inferior sustituido con hidroxi, -(CH2)2C(O)NH2, bencilo, fenilo, -CH2-grupo heterocíclico aromático de cinco miembros, CH2-indolilo, -CH2- cicloalquilo, cicloalquilo -(CH2)2-S-alquilo inferior； R3'es hidrógeno o alquilo inferior； o X es -C(O)-CHR4-CHR4'-C(O)-NH- CH2-； R4/R4'son hidrógeno o uno de R4 o R4' es amino； o es 0 o 1； o a una sal de adición de ácido farmacéuticamente aceptable, a una mezcla racémica o a sus enantiómeros y/o isómeros ópticos de
