Structure–activity relationship of a series of cyclohexylpiperidines bearing an amide side chain as antagonists of the human melanocortin-4 receptor

Approaches to the rational design of selective melanocortin receptor antagonists

INTRODUCTION

When establishing the physiological roles of specific receptors in normal and disease states, it is critical to have selective antagonist ligands for each receptor in a receptor system with several subtypes. The melanocortin receptors have five subtypes referred to as the melanocortin 1 receptor, melanocortin 2 receptor, melanocortin 3 receptor, melanocortin 4 receptor and melanocortin 5 receptor, and they are of critical importance for many aspects of human health and disease.

AREAS COVERED

This article reviews the current efforts to design selective antagonistic ligands for the five human melanocortin receptors summarizing the currently published orthosteric and allosteric antagonists for each of these receptors.

EXPERT OPINION

Though there has been progress, there are still few drugs available that address the many significant biological activities and diseases that are associated with these receptors, which is possibly due to the lack of receptor selectivity that these designed ligands are currently showing. The authors believe that further studies into the antagonists' 3D conformational and topographical properties in addition to future mutagenesis studies will provide greater insight into these ligands which could play a role in the treatment of various diseases in the future.

Complete experimental and theoretical proton and carbon nuclear magnetic resonance spectral assignments, molecular structure and conformational study of 1-cyclohexylpiperazine and 1-(4-pyridyl)piperazine

The possible stable forms and molecular structures of 1-cyclohexylpiperazine (1-chpp) and 1-(4-pyridyl)piperazine (1-4pypp) molecules have been studied experimentally and theoretically using nuclear magnetic resonance(NMR) spectroscopy. (13)C, (15)N cross-polarization magic-angle spinning NMR and liquid phase (1)H, (13)C, DEPT, COSY, HETCOR and INADEQUATE NMR spectra of 1-chpp (C(10)H(20)N(2)) and 1-4pypp (C(9)H(13)N(2)) have been reported. Solvent effects on nuclear magnetic shielding tensors have been investigated using CDCl(3), CD(3) OD, dimethylsulfoxide (DMSO)-d(6), (CD(3))(2)CO, D(2)O and CD(2)Cl(2). (1)H and (13)C NMR chemical shifts have been calculated for the most stable two conformers, equatorial-equatorial (e-e) and axial-equatorial (a-e) forms of 1-chpp and 1-4pypp using B3LYP/6-311++G(d,p)//6-31G(d) level of theory. Results from experimental and theoretical data showed that the molecular geometry and the mole fractions of stable conformers of both molecules are solvent dependent.

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 beta-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.

Structure–activity relationship studies on a series of cyclohexylpiperazines bearing a phanylacetamide as ligands of the human melanocortin-4 receptor

Synthesis and structure-activity relationship studies of a series of cyclohexylpiperazines bearing an amide side chain as ligands of the MC4 receptor are discussed. Compounds such as 11i from this series are potent agonists (EC(50)=33nM, IA=96%).