HCV protease inhibitors and uses thereof

1. A compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

one of R a and R b is hydrogen and the other is —OH or —OC(O)R′, or R a and R b are taken together to form an oxo group;

R′ is an optionally substituted group selected from C 1-6 aliphatic, C 3-7 cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or 4-7 membered heterocyclyl having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

R x and R y are taken together to form an optionally substituted C 3-7 membered ring having 0-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

R 1 is an optionally substituted group selected from C 1-6 aliphatic or C 3-7 cycloalkyl(C 1-3 alkyl);

R 2 is hydrogen or an optionally substituted group selected from C 1-6 aliphatic or C 3-7 cycloalkyl;

R 3 is a warhead group —(CH 2 ) n -L-Y, wherein n is an integer from 0 to 5, inclusive, and -L-Y is selected from the following:

(l) L is a covalent bond and Y is selected from:

(iv) a saturated 3-4 membered heterocyclic ring having 1 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-2 R e groups; or

(v) a saturated 5-6 membered heterocyclic ring having 1-2 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-4 R e groups; or

(xi) a partially unsaturated 4-6 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups; or

(xiii) a 6-membered aromatic ring having 0-2 nitrogens wherein said ring is substituted with 1-4 R e groups; or

(xv) a 5-membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-3 R e groups; or

(xvii) an 8-10 membered bicyclic aryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups;

(m) L is —C(O)— and Y is selected from:

(iv) a saturated 3-4 membered heterocyclic ring having 1 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-2 R e groups; or

(v) a saturated 5-6 membered heterocyclic ring having 1-2 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-4 R e groups; or

(xi) a partially unsaturated 4-6 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups; or

(xiii) a 6-membered aromatic ring having 0-2 nitrogens wherein said ring is substituted with 1-4 R e groups; or

(xv) a 5-membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-3 R e groups; or

(xvii) an 8-10 membered bicyclic aryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups;

(n) L is —N(R)C(O)— and Y is selected from:

(iv) a saturated 3-4 membered heterocyclic ring having 1 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-2 R e groups; or

(v) a saturated 5-6 membered heterocyclic ring having 1-2 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-4 R e groups; or

(xi) a partially unsaturated 4-6 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups; or

(xiii) a 6-membered aromatic ring having 0-2 nitrogens wherein said ring is substituted with 1-4 R e groups; or

(xv) a 5-membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-3 R e groups; or

(xvii) an 8-10 membered bicyclic aryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups;

(o) L is a bivalent C 1-8 saturated or unsaturated, straight or branched, hydrocarbon chain; and Y is selected from:

(iv) a saturated 3-4 membered heterocyclic ring having 1 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-2 R e groups; or

(v) a saturated 5-6 membered heterocyclic ring having 1-2 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-4 R e groups; or

(xi) a partially unsaturated 4-6 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups; or

(xiii) a 6-membered aromatic ring having 0-2 nitrogens wherein said ring is substituted with 1-4 R e groups; or

(xv) a 5-membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-3 R e groups; or

(xvii) an 8-10 membered bicyclic aryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups;

(p) L is a covalent bond, —CH 2 —, —NH—, —C(O)—, —CH 2 NH—, —NHCH 2 —, —NHC(O)—, —NHC(O)CH 2 OC(O)—, —CH 2 NHC(O)—, —NHSO 2 —, —NHSO 2 CH 2 —, —NHC(O)CH 2 OC(O)—, or —SO 2 NH—; and Y is selected from:

(iv) a saturated 3-4 membered heterocyclic ring having 1 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-2 R e groups; or

(v) a saturated 5-6 membered heterocyclic ring having 1-2 heteroatom selected from oxygen or nitrogen wherein said ring is substituted with 1-4 R e groups; or

(xi) a partially unsaturated 4-6 membered heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups; or

(xiii) a 6-membered aromatic ring having 0-2 nitrogens wherein said ring is substituted with 1-4 R e groups; or

(xv) a 5-membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-3 R e groups; or

(xvii) an 8-10 membered bicyclic aryl ring having 0-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, wherein said ring is substituted with 1-4 R e groups;

each R e is independently selected from -Q-Z, oxo, NO 2 , halogen, CN, a suitable leaving group selected from alkoxy, sulphonyloxy, optionally substituted alkylsulphonyloxy, optionally substituted alkenylsulfonyloxy, optionally substituted arylsulfonyloxy, acyl, diazonium, or C 1-6 aliphatic optionally substituted with oxo, halogen, NO 2 or CN, wherein:

Q is a covalent bond or a bivalent C 1-6 saturated or unsaturated, straight or branched, hydrocarbon chain, wherein one or two methylene units of Q are independently replaced by —N(R)—, —S—, —O—, —C(O)—, —OC(O)—, —C(O)O—, —SO—, or —SO 2 —, —N(R)C(O)—, —C(O)N(R)—, —N(R)SO 2 — or —SO 2 N(R)—; and

each Z is independently hydrogen or C 1-6 aliphatic optionally substituted with oxo, halogen, NO 2 or CN;

R 4 is —NHC(O)NHR 5 , —NHC(O)OR 6 , or

R 5 is an optionally substituted group selected from C 1-6 aliphatic, bridged bicyclic, 6-10 membered aryl, 5-10 membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or 4-7 membered heterocyclyl having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

R 6 is an optionally substituted group selected from C 1-6 aliphatic, bridged bicyclic, 6-10 membered aryl, 5-10 membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or 4-7 membered heterocyclyl having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;

R 7 is an optionally substituted group selected from C 1-6 aliphatic, bridged bicyclic, 6-10 membered aryl, 5-10 membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or 4-7 membered heterocyclyl having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; and

R is hydrogen or an optionally substituted group selected from C 1-6 aliphatic, C 3-7 cycloalkyl, 6-10 membered aryl, 5-10 membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or 4-7 membered heterocyclyl having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

2. The compound according to claim 1 , wherein the compound is of formula II-a or II-b:

or a pharmaceutically acceptable salt thereof.

3. The compound according to claim 2 , wherein the compound is of formula III-a or III-b:

or a pharmaceutically acceptable salt thereof, wherein:

R 2 is an optionally substituted group selected from C 1-6 aliphatic or C 3-7 cycloalkyl.

4. The compound according to claim 2 , wherein the compound is of formula IV-a or IV-b:

or a pharmaceutically acceptable salt thereof.

5. The compound according to claim 2 , wherein the compound is of formula V-a or V-b:

or a pharmaceutically acceptable salt thereof.

6. The compound according to claim 4 , wherein the compound is of formula IV-a-1 or IV-a-2:

7. The compound according to claim 4 , wherein the compound is of formula IV-b-1 or IV-b-2:

8. The compound according to claim 5 , wherein the compound is of formula V-a-1 or V-a-2:

9. The compound according to claim 5 , wherein the compound is of formula V-b-1 or V-b-2:

10. The compound according to claim 1 , wherein R 3 is selected from:

wherein each R e is independently a suitable leaving group, NO 2 , CN, or oxo.

11. A composition comprising a compound according to claim 1 , and a pharmaceutically acceptable adjuvant, carrier, or vehicle.

12. The composition according to claim 11 , in combination with an additional therapeutic agent.

13. The composition according to claim 12 , wherein the additional therapeutic agent is an antiviral agent.