Synthesis and biological evaluation of novel triptolide analogues for anticancer activity.

Three types of novel triptolide analogues with 9,11-olefin (3-5), five-membered unsaturated lactam ring (6-7) or A/B cis ring junction (8-14) were synthesized. Although with 9,11-olefin instead of 9,11-β-epoxide, compound 4a was much more active than the parent natural triptolide (1) with the lowest IC(50) value of 0.05nM for SKOV-3 cells, clearly challenging the traditional viewpoint on the necessity of 9,11-β-epoxide group of triptolide. In addition, structure-activity relationships for three classes of compounds were studied.