Synthesis and biological evaluation of colchicine and thiocolchicine derivatives bearing a Michael acceptor moiety in ring A

A series of colchicine and thiocolchicine derivatives bearing a Michael acceptor moiety in ring A were synthesized. Some of these compounds exhibit cytotoxic activity in the nanomolar range, efficiently disrupt the mitotic spindle, and cause the accumulation of G2/M-phase cells resulting in the development of apoptosis. These derivatives can be covalently bound to the cysteine residues at the colchicine-binding site of tubulin.