CA4 and neoplasm: By displacing the ethylene bridge with a 1,4-diaryl-2-azetidinone (β-lactam) ring in the combretastatin structure, cis-trans isomerization was prevented and a group of cis restricted CA-4 derivatives was synthesized by Nathwani et al. The effect of synthesized β-lactam compounds on tumor vascularization and its effect on tumor cell migration were investigated.