Design, synthesis, and SAR studies on a series of 2-pyridinylpiperazines as potent antagonists of the melanocortin-4 receptor

A series of 2-pyridinylpiperazines derived from β-Ala-(2,4-Cl)Phe dipeptide was synthesized for the study of their SARs and possible interactions with the MC4 receptor. Compounds such as 11k (Ki = 6.5 nM) possessed high potency.