Optimization of Subsite Binding to the β5 Subunit of the Human 20S Proteasome Using Vinyl Sulfones and 2-Keto-1,3,4-oxadiazoles: Syntheses and Cellular Properties of Potent, Selective Proteasome Inhibitors
作者:Robert M. Rydzewski、Leland Burrill、Rohan Mendonca、James T. Palmer、Mark Rice、Ram Tahilramani、Kathryn E. Bass、Ling Leung、Erik Gjerstad、James W. Janc、Lin Pan
DOI:10.1021/jm058289o
日期:2006.5.1
Beginning with the peptide sequence Cbz-Ile-Glu(OtBu)-Ala-Leu found in PSI (3), a series of vinyl sulfones (VS) were synthesized for evaluation as inhibitors of the chymotrypsin-like activity of the 20S proteasome. Variations at the key P3 position confirmed the importance of a long side chain capped with a hydrophobic group for optimal potency, consistent with a model of binding to the S3 subsite. The tert-butyl glutamic ester initially used at P3 gave plasma unstable, insoluble compounds and was replaced with the better isostere, N-beta-neopentyl asparagine. The inhibitors were shortened by replacing the N-terminal Cbz-isoleucine with a p-tosyl group without loss of potency. Small L-amino acids were used at P2, where D-substitution was not tolerated. The resulting optimized P4-P3-P2 sequence was grafted onto a novel proteasome inhibitor warhead, 2-keto-1,3,4-oxadiazoles (KOD), to produce reversible, subnanomolar proteasome inhibitors that were 1000-fold selective versus cathepsin B (CatB), cathepsin S (CatS), and trypsin-like as well as PGPH-like proteasome activity. A number of compounds in both the VS and the KOD series exhibited growth inhibitory effects against the human prostate cancer cell line PC3 at submicromolar concentrations.