Combinatorial Synthesis of Tetrasubstituted Alkenes and Related Compounds with Potential Anticancer Activity.

Objective: In search of efficient anticancer agents, we aimed at the design and synthesis of a library of tetrasubstituted alkenes. These are structural analogues of tamoxifen, one of the widely used anticancer therapeutics.

Methods: Our small organic compound library was prepared via a chemical synthesis in the solution using the Larock three-component coupling reaction, which is known to tolerate diverse functional groups. Further, we have integrated this synthetic approach to four- and fivecomponent alkene assembly by using Sonogashira coupling, A3 and AHA reactions. The final products were isolated through preparative LC/MS station and characterized by NMR, MS, and X-ray crystallography. The biological activity of all novel compounds was tested by luciferase reporter assays against estrogen receptor (ER) and androgen receptor (AR).

Results and discussion: Our combinatorial synthetic approach was based on structurally diverse internal alkynes, arylboronic acids and aryl halides. After experiment optimization a "one-pot" single synthetic procedure was developed. This allowed us to prepare a small-sized screening library of novel tetrasubstituted alkenes quickly and efficiently without laborious intermediate isolation. In most cases, we isolated the final product as a single isomer, and in selected cases, we confirmed their chemical structure via X-ray crystallography. High throughput screening of the novel tetrasubstituted alkenes revealed a dozen hits with predominant agonistic ERα- and antagonistic AR-activity in the micromolar range.

Conclusion: The proposed combinatorial approach is applicable for the synthesis of diversified organic compound libraries and for the discovery of new tamoxifen analogues with an improved therapeutic profile.