Asymmetrically Substituted m-Terphenyl Phosphates Inhibit the Transcription Factor STAT5a.

We recently presented Stafia-1 as the first chemical entity that inhibits the transcription factor STAT5a with selectivity over the highly homologous STAT5b. Stafia-1, which was identified from a series of symmetrically substituted m-terphenyl phosphates, binds to the interface between the SH2 domain and the linker domain of STAT5a. Here, we outline a synthetic strategy for the synthesis of asymmetrically substituted m-terphenyl phosphates, which can be tailored to address their asymmetric STAT5a binding site in a more specific manner. The asymmetrically substituted m-terphenyl phosphate with the highest activity against STAT5a was converted to a phosphatase-stable monofluoromethylene phosphonate. The synthetic methodology and activity analysis described here provide first insights into the structure-activity relationships of m-terphenyl phosphates for use as selective STAT5a inhibitors.