Peptides and their use as inhibitors of hepatitis C virus ns3 protease

A compound of Formula (I), or a pharmaceutically acceptable salt or ester thereof:

• wherein Q is:
• wherein X is —CH2— or —O—;
• Y is a group of formula —C(Ra)2— where each Ra is independently selected from hydrogen, hydroxyl, carboxylic acid, lower alkyl, aryl, heteroaryl, aralkyl and heteroalkyl, or the two Ra groups together form a cycloalkyl group containing 3 to 7 carbon atoms;
• Z is a substituted or unsubstituted aryl or heteroaryl group;
• R2 is a lower alkyl group, optionally substituted with one or more fluorine atoms, or is —CH2SH;
• Rd is hydrogen, lower alkyl, lower alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, hydroxyl, alkoxy, aryloxy, heteroaryloxy, aralkoxy, heteroaralkoxy, thioether, sulfonyl or sulfoxide;
• R4 is an alkyl, alkenyl, aralkyl, heteroaralkyl, aryl or heteroaryl group containing from 2 to 16 carbon atoms or is an acidic group;
• R5 selected from (R6)2NCO—, R7CO—, R7OCO—, R7NHCO—, R7CO.CO—, R7S(O)2— and R8 pep;
• each R6, independently, is selected from hydrogen and optionally substituted, optionally interrupted lower alkyl or lower alkenyl, aryl, heteroaryl, aralkyl or heteroaralkyl groups, or the two R6 taken together form a four to seven membered ring optionally containing one or more other heteroatoms in addition to the nitrogen atoms to which the R6 groups are bonded;
• R7 is an optionally substituted, optionally interrupted alkyl, alkenyl, aralkyl, heteroaralkyl, aryl or heteroaryl group containing from 1–18 carbon atoms;
• R8 is a group of formula (R6)2NCO—, R7CO—, R7 OCO—, R7NHCO—, R7 COCO—, or R7 S(O)2—;
• “pep” if present is an amino acid, di, or tri peptide of formula C-B-A;
• wherein A is selected from naturally and non-naturally occurring amino acids having a hydrophobic side chain containing 1–20 carbon atoms;
• B is optionally absent, in which case C will also be absent, but if present is selected from naturally and non-naturally occurring amino acids having a side chain which includes an acidic functionality;
• C is optionally absent, either by itself or together with B, but if present is selected from naturally and non-naturally occurring amino acids containing an acidic functionality;
• R17 is hydrogen, a lower alkyl, lower alkenyl, aryl, heteroaryl, aralkyl, heteroaralkyl, hydroxyl, alkoxy, aryloxy, aralkoxy, heteroaralkoxy, thioether, sulfonyl or sulfoxide group;
• R18 is:
• R19 is alkyl, C3–C7 cycloalkyl, or optionally substituted aryl;
• and
• each Re is independently hydrogen, lower alkyl, lower alkenyl, lower alkoxy, optionally substituted aryl, heteroaryl, aralkyl or heteroaralkyl;
• or two Re taken together form a three to seven membered aliphatic or aromatic ring which optionally contains at least one heteroatom, wherein when two Re are taken together in the formation of a ring containing unsaturation, then other Re may be absent.