SCH 430765 and SCH 500496 are potent and selective antagonists of the NPY5 receptor. NPY5 receptor antagonists have the potential for the treatment of obesity. [S-35]SCH 500946 was prepared for a competition binding assay which led to the identification of SCH 430765. Three distinct isotopically labelled forms of SCH 430765 were synthesized. [H-3]SCH 430765 was prepared for a preliminary absorption, distribution, metabolism and excretion data evaluation of the compound and [C-14]SCH 430765 for more definitive absorption, distribution, metabolism and excretion data work. In addition, [C-13(2),H-2(4)]SCH 430765 was prepared as an internal standard for a LC-MS bioanalytical method. The paper discusses the synthesis of 3 isotopically labelled forms of SCH 430765 and [S-35]SCH 500946.
