Substituted pyrrolo[3,4-d]imidazoles as JAK inhibitors

A compound of formula (I):

• or a pharmaceutically acceptable salt or optical isomer thereof,
• wherein:
• L is —CH2—, —C(O)—, or —S(O)2—;
• ring A is C3-7 cycloalkyl, a 3-7 membered heterocycloalkyl, a monocyclic C5-7 aryl, a bicyclic C7-11 aryl, a monocyclic 5-7 membered heteroaryl, a bicyclic 7-11 membered heteroaryl, or an 11-15 membered tricyclyl;
• each R1 is independently halogen, CN, C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl, OH, OC1-8 alkyl, C3-7 cycloalkyl, a 3-7 membered heterocycloalkyl, a monocyclic C5-7 aryl, a bicyclic C7-11 aryl, a monocyclic 5-7 membered heteroaryl, or a bicyclic 7-11 membered heteroaryl;
• wherein each C1-8 alkyl, C2-8 alkenyl, C2-8 alkynyl, and OC1-8 alkyl is optionally and independently substituted with 1, 2, 3, or 4 independently selected R3 substituents;
• and
• wherein each C3-7 cycloalkyl, 3-7 membered heterocycloalkyl, monocyclic C5-7 aryl, bicyclic C7-11 aryl, monocyclic 5-7 membered heteroaryl, and bicyclic 7-11 membered heteroaryl is optionally and independently substituted with 1, 2, 3, or 4 independently selected R4 substituents;
• each R2 is independently halogen, CN, NO2, C1-6 alkyl, OH, OC1-6 alkyl, or OC1-6 haloalkyl, wherein each C1-6 alkyl is optionally and independently substituted with 1, 2, or 3 substituents independently selected from the group consisting of halogen, CN, C1-4 alkyl, C1-4 haloalkyl, OH, OC1-4 alkyl, and OC1-4 haloalkyl;
• each R3 is independently halogen, CN, C1-3 alkyl, C(O)NR7R8, NR5R6, OH, OC1-6 alkyl, or a 3-7 membered heterocycloalkyl, wherein each 3-7 membered heterocycloalkyl is optionally and independently substituted with 1, 2, 3, or 4 independently selected R4 substituents;
• each R4 is independently halogen, C1-3 alkyl, NH2, NHCH3, N(CH3)2, OH, or OC1-6 alkyl;
• each R5 is independently H or C1-4 alkyl;
• each R6 is independently H or C1-4 alkyl;
• each R7 is independently H or C1-4 alkyl;
• each R8 is independently H or C1-4 alkyl;
• and
• each X is independently CH.