Olopatadine can be obtained by means of a process comprising hydrolysis of a compound of general formula (II), wherein Y is OR 1 , wherein R 1 is C 1 -C 7 alkyl, C 3 -C 7 cycloalkyl, aryl, or heterocycle； or NR 2 R 3 , wherein R 2 and R 3 , independently from each other, are C 1- C 7 alkyl, aryl, or R 2 and R 3 together with the nitrogen atom to which they are bound form a heterocycle of 3 to 7 members, obtained by means of a process comprising reacting the corresponding ester or amide of 6,11-dihydro-11-oxodibenz[ b,e ]oxepin-2-acetic acid with a suitable Witting reagent, in the presence of a base in a reaction medium comprising an organic solvent.
