The invention concerns aminopiperidine derivatives of general formula (I) wherein: Ra, Ra' and R5 represent hydrogen atoms or alkyl groups; R1 represent a hydrogen atom and an alkyl, cycloalkyl, heterocycloalkyl or aryl group; R2 represents a group of formula -(CH2)x-(CO)y-Y or -(CO)y-(CH2)x-Y, wherein Y represents a hydrogen atom or a hydroxy, alkyl, cycloalkyl, alkoxy, aryl, heteroaryl or NR 11R12 group, Y being other than a hydrogen atom when x = y = 0; R3 represents 1 to 3 groups selected among halogen atoms and alkyl, cycloalkyl, -OR, -NRR', -CO-NRR', -NR-CO-R', -NR-CO-NRR', -NR-COOR', -NO2, -CN and COOR groups; R4 is selected among groups of formula (a), (b) and (c), wherein p = 0, 1, 2 or 3, m = 0, 1 or 2; X represents an oxygen or sulphur atom or a -C(R 6)(R7)- or -N(R10)- member. The invention also concerns a method for preparing said derivatives and their therapeutic use as melanocortin receptor agonists for treating obesity, diabetes, sexual dysfunction.