A compound, or pharmaceutically acceptable salt thereof, having a formula I of: wherein R1 is H or optionally-substituted alkyl; R2 is optionally-substituted alkyl; R3 and R4 are each independently H or optionally-substituted alkyl; R5 is H, optionally-substituted alkyl, acyl, or alkoxycarbonyl; R6 and R7 are each independently H, deuterium, optionally-substituted alkyl, or R6 and R7 together form a carbocyclic; R8 is optionally-substituted thiazolyl, optionally-substituted thiophenyl, or substituted phenyl, provided that if R8 is 4-halophenyl, then R2 is substituted alkyl or branched alkyl or at least one of R6 or R7 is not H; and R30, R31 and R32 are each independently H, deuterium, halogen, substituted sulfanyl, or optionally-substituted alkoxy.