Peptidic p-nitroanilide substrates of interleukin-1β-converting enzyme

Peptidic p‐nitroanilides are useful colorimetric substrates for enzymes. With the aim of developing a convenient, quantitative assay for inhibitors of interleukin‐1β‐converting enzyme (ICE), we have explored three approaches to the synthesis of peptidic p‐nitroanilides relevant to this enzyme. The first approach involved a late stage oxidation of a p‐aminoanilide such as CbzValAlaAsp(β‐tert‐butyl)‐p‐(t‐Boc‐amino)anilide. The second and third approaches used the preformed amino acid p‐nitroanilides HAsp‐p‐nitroanilide hydrochloride and HAsp(7beta;‐tert‐butyl)‐p‐nitroanilide which were coupled iteratively with preactivated amino acid derivatives or with an appropriate peptide, respectively. While each approach had it merits and limitations, all three produced p‐nitroanilides that were substrates for ICE.