| The major focus of this dissertation is the use of modern medicinal chemistry techniques including, parallel synthesis of small-molecule libraries, cell-based biological activity assays, as well as ligand-based molecular modeling studies towards the discovery of new compounds as inhibitors of human equilibrative nucleoside transporters, hENT1 and hENT2. Chapter 1 provides an introduction to nucleoside transporters and their inhibitors, and therapeutic applications. Chapter 2 summarizes the research objectives of the thesis. Chapter 3 details the study of dipyridamole analogs as potent hENT1 and hENT2 inhibitors. A wide range of dipyridamole analogs were synthesized in this study and their in vitro inhibitory activities against hENT1 and hENT2 transporters were tested. Several dipyridamole analogs synthesized in this study demonstrated significantly better hENT1 and hENT2 inhibitory activities than the lead compound, dipyridamole. The most active compound (compound 161) exhibited 15-fold and 3-fold the activity of dipyridamole against hENT1 and hENT2, respectively. Chapter 4 covers the development of a novel fluorescent probe for hENT1 and hENT2. The probe is based on the most active compound disclosed in Chapter 3. This probe displays high and moderate affinity for hENT1 and hENT2, respectively, and has been demonstrated to be an effective probe for determining other compounds' hENT1 inhibitory activity by flow cytometry. Chapter 5 describes a study on draflazine analogs for their hENT1 and hENT2 inhibitory activity. An optimized synthetic scheme was designed that saves two synthetic steps, compared to what is reported in the literature. The in vitro activities of eleven newly synthesized flazine compounds, as well as an additional sixteen known analogs, were tested against hENT1 and hENT2 transporters. The biological results provide additional SAR information for this class of compounds with regard to their hENT1 and hENT2 inhibitory activities. Finally, Chapter 6 presents ligand-based CoMFA and CoMSIA 3D-QSAR studies for dipyridamole and draflazine analogs using the PHASE program for pharmacophore searching. QSAR models derived from this study provide design insights and predictive tools to guide further research on dipyridamole and draflazine analogs for their hENT1 and hENT2 inhibitory activities. |
