The proteasome is involved in many essential cellular functions,such as regulation of cell cycle,signal transduction pathways,antigen processing for appropriate immune responses,and apoptosis.1 Due to the importance of the proteasome,inhibition of the proteasome could become a useful therapeutic strategy for many diseases.A successful example of the development of protasome inhibitor is PS341(Bortezomib),which was approved in 2003 by FDA for the treatment of multiple myeloma.The co-crystal structure revealed that the active sites of 20S proteasome are located on the 1,2,and 5 subunits,which have caspase-,trypsin-,and chymotrypsin-like activities,respectively.Studies have shown that inhibition of the 5 alone is enough to attain therapeutic effects.2 Previously,we have reported a series of furan-based molecules with moderate potencies against proteasome β5 subunit.