A process for obtaining therapeutically active 2-[4-(3- and 2-(fluorobenzyloxy)benzylamino]propanamides and their salts with pharmaceutically acceptable acids with high purity degree, in particular, with a content of dibenzyl derivatives impurities lower than 0.03%, preferably lower than 0.01% by weight.The process is carried out by submitting the Schiff bases intermediates 2-[4-(3- and 2-fluorobenzyloxy)benzylideneamino]propanamides to catalytic hydrogenation in the presence of a heterogeneous catalyst in a protic organic solvent.