The invention relates to compounds of structural formulas (I) and (XVI):or a pharmaceutically acceptable salt, solvate, clathrate, or prodrug thereof, wherein X1, X2, Z, L, L2, R1, R2, R3, R21, n, q, and t are defined herein. These compounds are useful as immunosuppressive agents and for treating and preventing inflammatory conditions, allergic disorders, and immune disorders.
