A process of producing a compound of formula I or a pharmaceutically acceptable salt thereof, comprising contacting a compound of formula II with a coupling agent in an organic solvent to obtain a compound of formula I or a pharmaceutically acceptable salt thereof: wherein: R b is selected from H, halogen, cyano, and C 1 -C 6 alkyl; R 1 is H or C 1 -C 6 alkyl; R 2 is H or C 1 -C 6 alkyl; R 3 is selected from C 1 -C 6 alkyl and C OR 8; R 8 is selected from C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 10 cycloalkyl, and -CH 2 -C 3 -C 10 cycloalkyl, wherein C 3 -C 10 cycloalkyl is optionally substituted with one, two, or three C 1 -C 3 alkyl groups; R 4 and R 5 are independently selected from H, C 1 -C 6 alkyl, X, and C 1 -C 6 alkylene-X, wherein X is selected from: (i) C 3 -C 6 cycloalkyl; (ii) heteroaryl containing from 5 to 6 ring atoms wherein one, two, or three of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; (iii) heterocyclyl containing from three to six ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; and (iv) phenyl; wherein the C 3 -C 6 cycloalkyl, heterocyclyl, heteroaryl, and phenyl are each optionally substituted with one, two, or three substituents independently selected halogen, cyano, C 1 -C 6 alkyl, hydroxyl, and C 1 -C 6 alkoxy; or R 4 and R 5 together with the nitrogen to which they are attached form heterocyclyl containing from 4 to 6 ring atoms; wherein the heterocyclyl contains not more than two ring heteroatoms including the nitrogen atom attached to R 4 and R 5, and the second ring heteroatom, when present, is independently selected from N-C 1 -C 6 alkyl, O and S; and wherein the heterocyclyl is optionally substituted with one, two, or three substituents independently selected from halogen, cyano, C 1 -C 6 alkyl, and C 1 -C 6 alkoxy; R 6 is selected from -OH, C 1 -C 6 alkoxy, -OC -C 1 -C 6 alkyl, and -OC phenyl; and R 7 is H or C 1 -C 6 alkyl. R b is selected from H, halogen, cyano, and C 1 -C 6 alkyl; R 1 is H or C 1 -C 6 alkyl; R 2 is H or C 1 -C 6 alkyl; R 3 is selected from C 1 -C 6 alkyl and C OR 8; R 8 is selected from C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 10 cycloalkyl, and -CH 2 -C 3 -C 10 cycloalkyl, wherein C 3 -C 10 cycloalkyl is optionally substituted with one, two, or three C 1 -C 3 alkyl groups; R 4 and R 5 are independently selected from H, C 1 -C 6 alkyl, X, and C 1 -C 6 alkylene-X, wherein X is selected from: (i) C 3 -C 6 cycloalkyl; (ii) heteroaryl containing from 5 to 6 ring atoms wherein one, two, or three of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; (iii) heterocyclyl containing from three to six ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; and (iv) phenyl; wherein the C 3 -C 6 cycloalkyl, heterocyclyl, heteroaryl, and phenyl are each optionally substituted with one, two, or three substituents independently selected halogen, cyano, C 1 -C 6 alkyl, hydroxyl, and C 1 -C 6 alkoxy; (i) C 3 -C 6 cycloalkyl; (ii) heteroaryl containing from 5 to 6 ring atoms wherein one, two, or three of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; (iii) heterocyclyl containing from three to six ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from N, NH, N(C 1 -C 3 alkyl), O, and S; and (iv) phenyl; or R 4 and R 5 together with the nitrogen to which they are attached form heterocyclyl containing from 4 to 6 ring atoms; wherein the heterocyclyl contains not more than two ring heteroatoms including the nitrogen atom attached to R 4 and R 5, and the second ring heteroatom, when present, is independently selected from N-C 1 -C 6 alkyl, O and S; and wherein the heterocyclyl is optionally substituted with one, two, or three substituents independently selected from halogen, cyano, C 1 -C 6 alkyl, and C 1 -C 6 alkoxy; R 6 is selected from -OH, C 1 -C 6 alkoxy, -OC -C 1 -C 6 alkyl, and -OC phenyl; and R 7 is H or C 1 -C 6 alkyl.