Hcv protease inhibitors and uses thereof

A compound of formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• one of Ra and Rb is hydrogen and the other is —OH or —OC(O)R′, or Ra and Rb are taken together to form an oxo group;
• R′ is an optionally substituted group selected from C1-6 aliphatic, C3-7 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;
• Rx and Ry are taken together to form an optionally substituted C3-7 membered ring having 0-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
• R1 is an optionally substituted group selected from C1-6 aliphatic or C3-7 cycloalkyl(C1-3 alkyl);
• R2 is hydrogen or an optionally substituted group selected from C1-6 aliphatic or C3-7 cycloalkyl;
• R3 is a warhead group;
• R4 is —NHC(O)NHR5, —NHC(O)OR6, or
• R5 is an optionally substituted group selected from C1-6 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;
• R6 is an optionally substituted group selected from C1-6 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;
• R7 is an optionally substituted group selected from C1-6 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 C1-6 aliphatic, C3-7 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.