Compositions and methods for treating and preventing neurodegenerative disorders

A compound having:

• Formula IV-3a:
• or
• Formula IV-3b:
• or a pharmaceutically acceptable salt of any of the foregoing, wherein:
• Ra1 is selected from the group consisting of from hydrogen, and C1-C3 alkyl optionally substituted with one or more hydroxyl;
• Rb1 is selected from the group consisting of from hydrogen;
• C1-C5 alkyl substituted with one or more substituents independently selected from the group consisting of carboxy, amino, optionally substituted heteroaryl, optionally substituted aryl, alkylthio, aminocarbonyl, hydroxy, dialkylamino, alkylamino, and arylalkylamino;
• cycloalkyl optionally substituted with amino;
• and
• heterocyclyl optionally substituted with amino;
• R7 and R8 are each hydrogen;
• and
• ring A is selected from the group consisting of optionally substituted pyrrolidinyl, piperidinyl, morpholinyl, or piperazinyl.