Novel Alkyl Substituted Piperidine Derivatives and Their Use as Monoamine Neurotransmitter Re-Uptake Inhibitors

A piperazine derivative of the Formula I:

• any of its isomers or any mixture of its isomers,
• or a pharmaceutically acceptable salt thereof,
• wherein
• Ra represents hydrogen or alkyl;
• which alkyl is optionally substituted with one or more substituents independently selected from the group consisting of:
• halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxy, amino, nitro, alkoxy, cycloalkoxy, alkyl, cycloalkyl, cycloalkylalkyl, alkenyl and alkynyl;
• Rb represents an aryl or a heteroaryl group,
• which aryl or heteroaryl group is optionally substituted with one or more substituents independently selected from the group consisting of:
• halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxy, amino, nitro, alkoxy, cycloalkoxy, alkyl, cycloalkyl, cycloalkylalkyl, alkenyl and alkynyl;
• each of R2, R2′, R3, R3′, R5, R5′, R6 and R6′ independently of each other represents hydrogen or alkyl;
• with the proviso that at least one of R2, R2′, R3, R3′, R5, R5′, R6 and R6′ represents alkyl.