Compounds and compositions as protease inhibitors

A compound of Formula II:

• in which:
• X1 is selected from —C(O)—, —S(O)—, —C(S), —S(O)2— and —P(O)2—;
• R1 and R2 independently are hydrogen or (C1-6)alkyl;
• R3 and R4 independently are hydrogen or (C1-6)alkyl or R3 and R4 taken together with the carbon atom to which both R3 and R4 are attached form (C3-8)cycloalkylene;
• R5 and R6 independently are hydrogen or (C1-6)alkyl or R5 and R6 taken together with the carbon atom to which both R5 and R6 are attached form (C3-8)cycloalkylene or (C3-8)heterocycloalkylene;
• and
• R7 is —X2X3R9, wherein X2 is —C(O)—, —S(O)—, —C(S)—, —S(O)2— or —P(O)2—, X3 is a bond, —O— or —NR10—, wherein R10 is hydrogen or (C1-6)alkyl, and R9 is (C3-6)cycloalkyl(C0-6)alkyl, hetero(C3-6)cycloalkyl(C0-6)alkyl, phenyl(C0-6)alkyl or hetero(C5-6)aryl(C0-6)alkyl, wherein within R9 said cycloalkyl, heterocycloalkyl, phenyl or heteroaryl is substituted by —R12, —X4NR11R12, —X4NR11C(O)R12, —X4NR11C(O)OR12, —X4NR11C(O)NR11R12, —X4NR11C(NR11)NR11R12, —X4OR12, —X4SR12, —X4S(O)R12, —X4S(O)2R12, —X4C(O)R12, —X4C(O)OR12, —X4OC(O)R12, —X4C(O)NR11R12, —X4OC(O)NR11R12, —X4S(O)2NR11R12, —X4P(O)(OR11)OR12 or —X4OP(O)(OR11)OR12, wherein X4 is a bond or (C1-6)alkylene, R11 at each occurrence is hydrogen or (C1-6)alkyl and R12 is (C3-6)cycloalkyl(C0-6)alkyl, hetero(C3-6)cycloalkyl(C0-6)alkyl, phenyl(C0-6)alkyl or hetero(C5-6)aryl(C0-6)alkyl, wherein within R12 said cycloalkyl, heterocycloalkyl, phenyl or heteroaryl is substituted by —R13, —X4NR11R13, —X4NR11C(O)R13, —X4NR11C(O)OR13, —X4NR11C(O)NR11R13, —X4NR11C(NR11)NR11R13, —X4OR13, —X4SR13, —X4S(O)R13, —X4S(O)2R13, —X4C(O)R13, —X4C(O)OR13, —X4OC(O)R13, —X4C(O)NR11R13, —X4OC(O)NR11R13, —X4S(O)2NR11R13, —X4P(O)(OR11)OR13 or —X4OP(O)(OR11)OR13, wherein X4 and R11 are as defined above and R13 is (C3-6)cycloalkyl(C0-6)alkyl, hetero(C3-6)cycloalkyl(C0-6)alkyl, phenyl(C0-6)alkyl or hetero(C5-6)aryl(C0-6)alkyl, wherein within R7 any alicyclic and aromatic rings present may be substituted further by 1 to 5 radicals independently selected from (C1-6)alkyl, (C1-6)alkylidene, cyano, halo, halo-substituted (C1-4)alkyl, nitro, —X5NR14R14, —X5NR14C(O)OR14, —X5NR14C(O)NR14R14, —X5NR14C(NR14)NR14R14, —X5OR14, —X5SR14, —X5C(O)OR14, —X5C(O)NR14R14, —X5S(O)2NR14R14, —X5P(O)(OR5)OR14, —X5OP(O)(OR5)OR14, —X5NR14C(O)R15, —X5S(O)R15, —X5S(O)2R15 and —X5C(O)R15, wherein X5 is a bond or (C1-6)alkylene, R14 at each occurrence independently is hydrogen, (C1-6)alkyl or halo-substituted (C1-3)alkyl and R15 is (C1-6)alkyl or halo-substituted (C1-3)alkyl;
• or a N-oxide derivative, individual stereoisomer or mixture of stereoisomers;
• or a pharmaceutically acceptable salt thereof.