Synthesis and characterization of pyrrolidine derivatives as potent agonists of the human melanocortin-4 receptor

A series of trans-4-phenylpyrrolidine-3-carboxamides were synthesized and characterized as potent ligands of the human melanocortin-4 receptor. Interestingly, a pair of diastereoisomers 20f-1 and 20f-2 displayed potent functional agonist and antagonist activity, respectively. Thus, the 3S,4R-compound 20f-1 possessed a Ki of 11 nM and an EC50 of 24 nM, while its 3R,4S-isomer 20f-2 exhibited a Ki of 8.6 and an IC50 of 65 nM. Both compounds were highly selective over other melanocortin receptor subtypes. The MC4R agonist 20f-1 also demonstrated efficacy in diet-induced obese rats.

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