A compound of formula (VIII) or a pharmaceutically acceptable salt thereof, ** Formula ** where R1 and R2 are each independently C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, each being optionally substituted by 1 -4 R5； L is NR6C (O) or C (O) NR6, R3a is carbocycle, heterocyclyl, aryl, heteroaryl, and R3b is a 6-membered nitrogen-containing heteroaryl, each optionally substituted by 1-4 R7； each R5 is independently halo, hydroxy, alkoxy, amino, alkylamino, dialkylamino, cyano, nitro, amido, mido alkylation, dialkylamido, thioyl, sulfonyl, carbocycle, heterocyclyl, aryl, or heteroaryl； each R6 is independently H, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 hydroxy alkyl, C1-C6 alkoxy alkyl, cyanoalkyl, haloalkyl, arylalkyl, S (O) alkyl, acyl, amino, amidyl, S (O) 2H, aryl, or alkoxyaryl； Each R7 is independently C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halo, hydroxyl, alkoxy, oxo, aryl, heteroaryl, carbocycle, heterocyclyl, arylalkyl, heteroarylalkyl, cyclolalkyl, heterocyclylalkyl, aryloxy, arylamino alkoxy, , dialkylamino, thioyl, alkylthioyl, sulfonyl, sulfonamidyl, amido (for example, where the amide nitrogen is substituted by an alkyl group, or where the amide nitrogen together with two carbons to which it is attached, forms a ring ), hydroxyl alkoxy, alkoxy-C (O) OH, -C (O) Oalkyl, urea, sulfonylurea, acyl, nitro, or cyano, each optionally substituted with 1-3 R8； each R8 is independently C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halo, hydroxy, alkoxy, oxo, aryloxy, amino, alkylamino, dialkylamino, C (O) OH, -C (O) O alkyl, thioyl , sulfonyl, sulfonamidyl, amido (for example, where the amide nitrogen is substituted by an alkyl group, or where the amide nitrogen together with two carbons to which it is attached, forms a ring), urea, sulfonylurea, acyl, nitro, cyano, carbocycle, heterocyclyl, aryl, or heteroaryl； R9 is H, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, halo, C1-C6 haloalkyl, hydroxyl, alkoxy, aryloxy, arylalkoxy, amino, alkylamino, dialkylamino, thioyl, alky
