Design and NMR conformational analysis in solution of β5i-selective inhibitors of immunoproteasome

The identification of effective and selective immunoproteasome inhibitors could greatly promote smart treatment of many autoimmune, inflammatory and tumor diseases. This paper explores the activity of some pyridone derivatives which are taking advantage of peptide mimicking moieties and other func- tional groups whose related effects are taken into consideration. The target compounds were designed and synthesized starting from a lead, next their in vitro biological activity was tested; the following struc- tural and conformational analysis sheds light over the different activity of the tested compounds. Com- pound 3 bearing a phenylalanine at the P2 site and an allyloxycarbonyl group spanning the P3 region, was found to be a selective inhibitor of β5 subunit of immunoproteasome. It has been demonstrated by Nuclear Magnetic Resonance (NMR) that, in solution, this substrate displays a more rigid conformation respect to the others, especially in apolar media, this feature is likely crucial for the enhancement of the activity towards immunoproteasome. The specific conformational analysis enables insights of the biolog- ical activity of new chemicals driving possible advancements based on the suitable structural features to identify novel selective β5 immunoproteasome inhibitor.