3-Haloacylamino benzoylureas (3-HBUs) consist of a new family of tubulin ligands that kill cancer cells through mitotic arrest. In exploring the structure–activity relationship (SAR), 17 analogues defined through variations of formylurea at the 1-position of the aromatic ring were synthesized. SAR analysis revealed that (i) the p–π conjugation between the aromatic ring and formylurea was essential;(ii) suitable aryl substitutions at the N′-end increased ...