Peptidic p-nitroanilide substrates of interleukin-1 beta-converting enzyme.

Peptidic p-nitroanilides are useful colorimetric substrates for enzymes. With the aim of developing a convenient, quantitative assay for inhibitors of interleukin-1 beta-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(beta- 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(beta-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.