The invention relates to compounds of structural formula (I):or a pharmaceutically acceptable salt, solvate, clathrate, and prodrug thereof, wherein Ra, Rb, and R2are defined herein. These compounds inhibit tubulin polymerization and/or target vasculature and are useful for treating proliferative disorders, such as cancer.本發明係關於結構式(I)的化合物:或其醫藥上可接受的鹽、溶劑合物、晶籠化合物、與前藥,其中Ra、Rb、與R2係於本發明中定義。這些化合物會抑制微管蛋白聚合作用及/或靶定血管系,且係有用於治療增生性疾病,例如癌症。