Synthesis of flavones, isoxazolines and related heterocycles: The search for small molecule drugs to treat cystic fibrosis

Small molecule heterocycles, principally flavones, have been synthesized and evaluated for their activity as effectors of the chloride channel CFTR (cystic fibrosis transmembrane conductance regulator). The aim of this thesis work was to find activators of CFTR for potential treatment of cystic fibrosis (CF).; Numerous flavones were prepared and evaluated for their CFTR activity using a high throughput fluorescence assay. Electrophysiological measurements were performed to assess and verify activity. The biological assays were performed on cells expressing wild type- or G551D-CFTR, a mutation of CFTR that results in CF. Interestingly, the structures of a potent class of compounds discovered during the course of this work, the 7,8-benzoflavones (e.g. UCCF-029), contained structural features of both the flavone and benzo[c]quinolizinium (a literature lead compound) ring systems.; To improve the activity of our lead compound UCCF-029, we probed the relevance of (i) the A-ring benzannulation and (ii) the B-ring pyridyl-nitrogen. The data show that benzannulation at the 7,8-positions of the flavone scaffold significantly activates wild type-CFTR. The position of the pyridyl B-ring nitrogen appears less influential. Dose-response data from both fluorescence and electrophysiological studies confirm that UC CF-339 (Kd = 1.7 muM), a C(6)-substituted analog of UCCF-029, has four-fold higher maximal activity than either UCCF-029 or apigenin (the most potent flavonoid activators of wild type-CFTR before UCCF-029). Computational analysis of the SAR data led to a consensus common features pharmacophore model that provides an emerging picture of the binding site for activators of CFTR.; We also developed a solid-phase synthetic route to isoxazoline/amides. The synthesis involved loading substrates containing aldehyde and alkene functionality onto Wang's resin. Subsequent reductive amination of the aldehyde moiety followed by acylation produced the new amide. The alkene moiety was reacted with nitrile oxides (1,3-dipolar cycloadditions) to afford the isoxazoline heterocyclic core. Unlike the flavone hits, the prototype compounds of this class had minimal CFTR activity.