The invention relates to compounds of structural formulas (I), (VII) and (XI):or a pharmaceutically acceptable salt, solvate, clathrate, or prodrug thereof, wherein X1, X2, X3, Y, Z, L, R1, R2, R3, R18 and n are defined herein. These compounds are useful as immunosuppressive agents and for treating and preventing inflammatory conditions, allergic disorders, and immune disorders.
