Gracilin a and congeners as immunosuppressive and neuroprotective agents

A method for treating a neurodegenerative disease in a subject, the method comprising administering to a subject in need thereof an effective amount of a compound having the formula:

• or a stereoisomer or racemate thereof, wherein:
• R1, R2, and R3 are independently H or C1-C3 alkyl;
• R4 is H, OH, OAc, or absent;
• R5 and R8 are independently H or OAc;
• R6 and R7 are H or R6 and R7, taken together, are O;
• and
• the dashed line denotes a bond when R4 is absent, or absence of a bond when R4 is H, OH, or OAc.

A compound having the formula:

• or a stereoisomer or racemate thereof, wherein:
• R1, R2, and R3 are independently H or C1-C3 alkyl;
• R4 is H, OH, OAc, or absent;
• R5 and R8 are independently H or OAc;
• R6 and R7 are H or R6 and R7, taken together, are O;
• and
• the dashed line denotes a bond or absence of a bond with the proviso that only one dashed line is a bond, and with a further proviso that both dashed lines denote absence of a bond when R4 is H, OH, or OAc.