Compositions and methods for treating and preventing neurodegenerative disorders

A compound of Formula IVa, IVb, IVc or IVa:

• a racemic mixture thereof, or a pharmaceutically acceptable salt of any of the foregoing, wherein:
• R1 is —SO3H, or —(CH2)nSO3H;
• R3 is —NRaRb, wherein:
• Ra is —H or optionally substituted alkyl;
• and
• Rb is selected from hydrogen, alkyl substituted with a carboxyl or a carboxylate, an amino acid or a dipeptide, wherein the amino acid or the dipeptide is bound to the nitrogen atom in R3 through a carboxy group;
• or
• Ra and Rb are taken together to form an optionally substituted heterocyclyl;
• Rz is an amino acid or a dipeptide;
• or
• R3 is —C(O)—NRaRb, wherein:
• Ra is —H or optionally substituted alkyl;
• and
• Rb is selected from hydrogen, optionally substituted cycloalkyl, optionally substituted heterocycloalkyl, and optionally substituted alkyl, or;
• Ra and Rb are taken together to form an optionally substituted heterocyclyl;
• or
• R3 is —C(O)Rz, wherein:
• Rz is selected from an amino acid or a dipeptide, wherein the amino acid or the dipeptide is bound to the carbon atom through an amino group;
• or optionally substituted alkyl;
• R4 is —H, —CH3, —(CH2)n OH, —NH2, —(CH2)nNH2, —C(O)NH2, or —(CH2)nC(O)NH2;
• n is 1 or 2;
• A1 is —CH2—, —NH—, or —C(O)—;
• A2 is —CH2—, —NH—, or —C(O)—;
• and
• A3 is —CH2—, —NH—, or —C(O)—.