Synthesis of 3 H, 13 C 2 , 2 H 4 14 C-SCH 430765 and 35 S-SCH 500946, potent and selective inhibitors of the NPY 5 receptor.

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. [35 S]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. [3 H]SCH 430765 was prepared for a preliminary absorption, distribution, metabolism and excretion data evaluation of the compound and [14 C]SCH 430765 for more definitive absorption, distribution, metabolism and excretion data work. In addition, [13 C2 ,2 H4 ]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 [35 S]SCH 500946.