Design, synthesis and biological evaluation of new agents targeting estrogen receptor-alpha and -beta

The two known estrogen receptors, ERalpha and ERbeta, are the products of different genes on separate chromosomes. Of these, ERalpha has been the most extensively studied, and its expression in breast cancer determines the ER+ phenotype. ERbeta, on the other hand, was discovered only recently and its role in breast cancer pathology remains unclear. ERbeta inhibits E2-induced proliferation of T47D breast cancer cells in addition to decreasing the expression of cell cycle related genes. Clinical studies have shown a positive correlation between ERbeta expression with disease-free survival and overall survival in breast cancer patients. ERbeta activation with a selective ERbeta agonist could antagonize the stimulating activity of the ERalpha in breast cancer cells, and such an ERbeta agonist could help overcome acquired resistance. Therefore, this work began a search for such agents.;A one-pot hydrozirconation-transmetallation-aldimine addition sequence that leads to allylic amides, homoallylic amides and C-cyclopropylalkylamides was significantly accelerated by microwave technology and used for library preparation. The conventional methodology provided a first generation discovery library. A potentially antiestrogenic compound was identified in a transcriptional screening assay from this library, C-cyclopropylalkylamide 26a (O-ethyl-N-{2-[(1S*,2 R*)-2-{(R*)[(diphenylphosphinoyl)amino](phenyl)methyl}cyclopropyl]ethyl}- N-[(4-methylphenyl)sulfonyl]carbamate; a.k.a. CK1-183).;Following up on these findings and with the goal to expand the scope of the synthesis methodology, a second generation library of allylic amides and C-cyclopropylalkylamides was prepared. The new library was screened in a fluorescence polarization based homogenous in vitro assay at ERalpha, and hits were further evaluated in cell-based assays. Three new C-cyclopropylalkylamides, 37c, 37a and 39c, were identified with improved potency over the lead agent 26a against 17beta-estradiol (E2) stimulated MCF-7 cells.;This second generation library was screened against both ERs. The screening results served to build an SAR model of allylic amides and C-cyclopropylalkylamides at ERalpha and ERbeta. A hit from the ERbeta screen, C-cyclopropylalkylamide 37d (N-(R*)-(((1R*,2 R*)-2-butylcyclopropyl)-(4-(phenyl)phenyl)methyl)benzamide), contained a biphenyl core and served as a starting point for the design and synthesis of a third generation of C-cyclopropylalkylamide ER targeting agents.;Biphenyl C-cyclopropylalkylamides represent novel structural scaffolds for design and synthesis of ERalpha and ERbeta targeting agents and a novel avenue for selective estrogen receptor modulator (SERM) development.