The present invention relates to a process for the preparation of compounds endowed with phosphodiesterase (PDE4) inhibitory activity having formula (I). The invention also relates to the process for the isolation by crystallization of the compound (I) and to its use for the preparation of pharmaceutical compositions for inhalation in combination with suitable carriers or vehicles. The present invention also relates to solvates and crystal forms of a compound of formula (I). The synthesized product is suitable for use in pharmaceutical applications for instance in the treatment of respiratory diseases.
