The synthesis and tubulin binding activity of thiophene-based analogues of combretastatin A-4

A number of analogues of combretastatin A-4 (1), containing a thiophene ring interposed between the two phenyl groups, have been prepared. The synthesis of these compounds employed a combination of palladium-mediated coupling and iodocyclization techniques. The thiophene compounds 11, 14, 18, and 19 also represent non-benzofused analogues of some recently described tubulin binding benzo[b]thiophenes 3–5. The most active thiophene compounds identified in this study were 11, 14, and 18. Overall they are less active than 1 but exhibit comparable activity to the most active of the benzo[b]thiophenes 3–5. A structure–activity relationship of these compounds is considered.