Novel indole derivatives and their use in neurodegenerative diseases

A compound of formula II, III, IV, V or IV:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is
• R2 is
• each RA is independently —R, halogen, -haloalkyl, -hydroxyalkyl, —OR, —SR, —CN, —NO2, —SO2R, —SOR, —C(O)R, —CO2R, —C(O)N(R)2, —NRC(O)R, —NRC(O)N(R)2, —NRSO2R, or —N(R)2;
• each R is independently hydrogen, C1-6 aliphatic, C3-10 aryl, a 3-8 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered heterocylic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
• each of which is optionally substituted;
• or
• two R groups on the same atom are taken together with the atom to which they are attached to form a C3-10 aryl, a 3-8 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered heterocylic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur;
• each of which is optionally substituted;
• provided that, if the compound is of formula II, R1 is not
• and provided that, if the compound is of formula III, R2 is not