Design and synthesis of carborane-containing androgen receptor (AR) antagonist bearing a pyridine ring

Compound 6b, which was designed based on the structures of BA321 and BA341, exhibited more potent antiandrogenic activity than that of flutamide in SC-3 cell growth inhibition assay. We previously developed carborane-containing potent AR antagonists, BA321 and BA341, on the basis of our hypothesis that the carborane cage would be an excellent hydrophobic pharmacophore in place of steroidal C and D rings. As an extension of that work, we designed and synthesized carborane-containing AR antagonist candidates with a pyridine ring. Compound 6b, which has a pyridine ring directly bound to the p-carborane cage at the 3-position, exhibited potent AR-antagonistic activity in transcriptional activation assay using NIH3T3 cells transfected with a hAR-expression plasmid. In addition, it showed more potent antiandrogenic activity than that of the well-known antiandrogen flutamide and comparable activity to that of ( R)-bicalutamide in SC-3 cell proliferation assay.