Conformationally Flexible Platelet Aggregation Inhibitors Based on the Tetrapeptide Arg-Gly-Asp-Arg

Summary A series of nonpeptide fibrinogen receptor antagonists based upon the tetrapeptide Arg-Gly-Asp-Arg were prepared. These relatively simple derivatives incorporate a high degree of conformational flexibility that was anticipated to allow them to attain the requisite conformation for binding to the platelet fibrinogen receptor. Optimization of the distances between the required acidic and basic functional groups led eventually to compound 7, which is a one hundred-fold more potent inhibitor of platelet aggregation than the peptide it is based upon.