Gyrase inhibitors and uses thereof

A compound of formula IA:

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is an optionally substituted group selected from a C1-6 aliphatic group, —C(R4)2(CH2)nNRCOR, —C(R4)═N—OR, —C(R4)═N—OC(═O)(C1-6 aliphatic), —C(R4)═NNRCO2(C1-6 aliphatic), —C(R4)═NNRCOR, —C(R4)═NN(R)2, —C(R4)2 (CH2)nNRCO2(C1-6 aliphatic), —CO2(C1-6 aliphatic), —CON(R)2, —C(R4)2(CH2)nCON(R)2, —C(R4)2(CH2)nSO2N(R)2, —CONH—OR, —SO2N(R)2, or —C(R4)2(CH2)nNRSO2(C1-6 aliphatic);
• n is zero or one;
• each R is independently selected from hydrogen or an optionally substituted C1-6 aliphatic group;
• R2 is selected from hydrogen or, when R1 is —CO2(C1-3 aliphatic) or —CONH(C1-3 aliphatic), R2 is further selected from -halo, —CN, —C1-4 aliphatic, a three to five-membered heterocyclyl, or a five-membered heteroaryl;
• R3 is an optionally substituted piperidinyl or pyridyl ring;
• each R4 is indepependently selected from hydrogen, an optionally subtituted C1-6 aliphatic group, or two R4 taken together with the carbon to which they are attached form a three to six membered aliphatic ring;
• each R5 is independently selected from hydrogen, an optionally subtituted C1-4 aliphatic group, or two R5 taken together with the nitrogen to which they are attached form a five or six membered heterocyclic ring;
• and
• Ar is an optionally substituted piperidinyl or pyridyl ring.