AM 114, a derivative of boronic chalcone, is a potent small-molecule inhibitor of the proteasome that inhibits the chymotrypsin-like activity of the 20S proteasome, with a value of 50% inhibition concentration IC50 of approximately 1 uM, resulting in a significant accumulation of ubiquitinated p53 and other cellular proteins in whole cells without significantly disrupting the interaction of p53 and murine double minute 2 (mdm2) proteins.