Synthesis of steroid analogs of tubuloclustin, their cytotoxicity and effect on microtubules of A549 carcinoma cells

Synthesis of analogs of tubuloclustin (N-(7-adamant-2-yloxy-7-oxoheptanoyl)-N-deacetylcolchicine (1)) with the colchicine fragment replaced with 2-methoxyestradiol scaffold attached via phenolic hydroxy group was described. Esters 3a–c exhibit moderate cytotoxicity (EC50 = 5–6 μmol L–1) and exert a weak effect on the microtubule network in A549 human lung carcinoma cells similar to the clustering effect of tubuloclustin and its derivatives. Conjugates 6a–c and 7a–c with the phenolic ester bond are low stable and compounds 7a–c are inactive to the microtubules of A549 cells, while compounds 6a–c cause an unusual effect of curling of the microtubules.