A compound having the structural formula Formula ** ** or a pharmaceutically acceptable salt or N-oxide thereof, wherein R1 is H, - (C1 - C4), -C (O) - (C1 - C4 ) or -C (O) O- (C1 - C4), and R2 is Formula ** ** where G is a bond, -CH2-, -C (H) (R16) -, -C (R16 ) 2-, L or -S (O) 2-, v is 0, 1, 2, 3 or 4, each R15 is selected, independently, from - (C1 - C6), - (C1 - C6), - (alkyl C0 - C6) -LR 7, - (alkyl C0 - C6) -NR8R9, - (alkyl C0 - C6) -OR10, - (alkyl C0 - C6) -C (O) R10, - (alkyl C0 - C6) -S (O) 0-2R10, -halogen, -NO2 and -CN and two R 15 on the same carbon optionally combine to form oxo, and R17 is aryl or heteroaryl, optionally substituted with 1, 2 or 3 substituents which are selected, independently, from - (C1 - C6), - (C1 - C6), - (alkyl C0 - C6) -L-R7, - (alkyl C0 - C6) -NR8R9, - (C0 - C6) -OR10, - (C0 - C6) - C (O) R10, - (C0 - C6) -S (O) 0-2R10, -halogen, -NO2 and -CN or R1 and R2 together with the nitrogen to which they are attached join to form wherein f is 0 or 1, g is 0, 1 or 2, c is 0, 1, 2, 3 or 4, G is a bond, -CH2-, -C (H) (R16) -, -C (R16) 2-, L or -S (O) 2-, R28 is aryl or heteroaryl, optionally substituted with 1, 2 or 3 substituents selected , independently, from - (C1 - C6), - (C1 - C6), - (alkyl C0 - C6) -L-R7, - (alkyl C0 - C6) -NR8R9, - (alkyl C0 - C6) -OR10, - (alkyl C0 - C6) -C (O) R10, - (alkyl C0 - C6) -S (O) 0-2R10, -halogen, -NO2 and -CN, each R21 is selected from independently, from - (C1 - C6), - (C1 - C6), - (alkyl C0 - C6) -LR 7, - (alkyl C0 - C6) -NR8R9, - (alkyl C0 - C6) -OR10 , - (C0 - C6) -C (O) R10, - (alkyl C0 - C6) -S (O) 0-2R10, -halogen, -NO2 and -CN, and two R21 on the same carbon optionally combine to form an oxo, E3 is NH N substituted by one of the c R21, N substituted with -G-R28, CH2, CH substituted by one of the c R21, CH substituted by the -G-R28, or C substituted with one of R21 and c - G-R28, and E4 is absent, NH, N substituted by one of the c R21, N substituted with -G-R28, CH2, CH substituted by one of the c
