Synthesis and structure–activity relationships of uracil derived human GnRH receptor antagonists: (R)-3-[2-(2-amino)phenethyl]-1-(2,6-difluorobenzyl)-6-methyluracils containing a substituted thiophene or thiazole at C-5

Abstract The synthesis of a series of ( R )-3-[2-(2-amino)phenethyl]-1-(2,6-difluorobenzyl)-6-methyluracils containing a substituted thiophene or thiazole at C-5 is described. SAR around C-5 of the uracil led to the discovery that a 2-thienyl or (2-phenyl)thiazol-4-yl group is required for optimal receptor binding. The best compound from the series had a binding affinity of 2 nM ( K i ) for the human GnRH receptor. A novel and convenient preparation of N -1-(2,6-difluorobenzyl)-6-methyluracil is also described.