Conformationally restricted macrocyclic analogues of combretastatins

New analogues of combretastatins have been evaluated as inhibitors of tubulin polymerization. These compounds present a macrocyclic structure, in which the para positions of the aromatic moieties have been linked by a 5- or 6-atoms chain, in order to produce a conformational restriction. This could contribute to determine the active conformation for these ligands. Such a conformational restriction and/or the steric hindrance makes them less potent inhibitors than the model compound CA-4.