Peptide-based inhibitors of hepatitis C virus full-length NS3 (protease-helicase/NTPase): Model compounds towards small molecule inhibitors

From L-alpha-aminobutyric acid (Abu) a set of electrophilic and non-electrophilic replacements for the PI cysteine of substrate and product inhibitors of hepatitis C virus full-length NS3 (protease-helicase/NTPase) serine protease have been synthesised and coupled to a model pentapeptide furnishing a set of hexapeptide inhibitors. Promising inhibitory activities with K-i values of 0.18muM (11b, P1 electrophilic alpha,beta-unsaturated ketone), 0.46 muM (12e, P1 electrophilic alkyl ketone) and 0.98muM (10e, P1 nonelectrophilic alkenyl alcohol as diastereomeric mixture). The reference hexapeptide product inhibitor had a K-i value of 1.54 muM (14, P1 Abu-OH). The electrophilic inhibitors exhibit increased potency as compared with the corresponding product inhibitor, and notably also the non-electrophilic P1 alkenyl alcohol 10e. This represents the first example of non-electrophilic inhibitors that are not P1 amides or product inhibitors. (C) 2003 Elsevier Science Ltd. All rights reserved.