Compounds of the following general formula (I): are provided. The compounds can be used as modulators of the proteasome activity, in the preparation of a medicament useful for the prevention or treatment of diseases wherein the proteasome is involved, such as diseases of inflammatory processes, various hematological and solid tumor cancers, immunological and autoimmune diseases, cardiac pathologies, myopathies, AIDS, cystic fibrosis, Alzheimer's and Parkinson's disease, or in the preparation of cosmetic compositions or phytosanitary compositions.