Polymer-Assisted solution-Phase (PASP) parallel synthesis of an α-Ketothiazole library as tissue factor VIIa inhibitors

A solution-phase synthesis of an α-ketothiazole library of the general form -Phe- -AA- -Arg-α-ketothiazole is described. The five-step synthesis is accomplished using a combination of polymeric reagents and polymer-assisted solution-phase purification protocols, including reactant-sequestering resins, reagent-sequestering resins, and tagged reagents. The multi-step synthesis affords the desired α-ketothiazole products in excellent purities and yields. A variety of -amino acid inputs were used to probe the S2 pocket of the tissue factor (TF) VIIa enzyme to influence both potency and selectivity. An X-ray crystal structure of compound 10e bound to the TF/VIIa complex was obtained that explains the observed selectivity. The α-ketothiazoles were found to be potent, reversible-covalent inhibitors of tissue factor VIIa, with some analogues demonstrating selectivity versus thrombin.