Design, Synthesis, and Characterization of Proteolytically-Stable Opioid-Neurotensin Hybrid Peptidomimetics.

Linking an opioid to a nonopioid pharmacophore represents a promising approach for reducing opioid-induced side effects during pain management. Herein, we describe the optimization of the previously reported opioid-neurotensin hybrids (OPNT-hybrids), & , containing the μ-/δ-opioid agonist H-Dmt-d-Arg-Aba-β-Ala-NH and NT(8-13) analogs optimized for NTS2 affinity. In the present work, the constrained dipeptide Aba-β-Ala was modified to investigate the optimal linker length between the two pharmacophores, as well as the effect of expanding the aromatic moiety within constrained dipeptide analogs, via the inclusion of a naphthyl moiety.

Novel Cocrystal Structures of Peptide Antagonists Bound to the Human Melanocortin Receptor 4 Unveil Unexplored Grounds for Structure-Based Drug Design.

Melanocortin 4 receptor (MC4-R) antagonists are actively sought for treating cancer cachexia. We determined the structures of complexes with and . These peptides differ from by substituting His with Pro and inserting Gly or Arg.

Opening the amino acid toolbox for peptide-based NTS2-selective ligands as promising lead compounds for pain management.

Chronic pain is one of the most critical health issues worldwide. Despite considerable efforts to find therapeutic alternatives, opioid drugs remain the gold standard for pain management. The administration of μ-opioid receptor (MOR) agonists is associated with detrimental and limiting adverse effects.

Comprehensive overview of biased pharmacology at the opioid receptors: biased ligands and bias factors.

One of the main challenges in contemporary medicinal chemistry is the development of safer analgesics, used in the treatment of pain. Currently, moderate to severe pain is still treated with the "gold standard" opioids whose long-term often leads to severe side effects. With the discovery of biased agonism, the importance of this area of pharmacology has grown exponentially over the past decade.

Using conformational constraints at position 6 of Angiotensin II to generate compounds with enhanced AT2R selectivity and proteolytic stability.

The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases.

Structure-Based Design of Melanocortin 4 Receptor Ligands Based on the SHU-9119-hMC4R Cocrystal Structure†.

The melanocortin receptors (MC1R-MC5R) belong to class A G-protein-coupled receptors (GPCRs) and are known to have receptor-specific roles in normal and diseased states. Selectivity for MC4R is of particular interest due to its involvement in various metabolic disorders, including obesity, feeding regulation, and sexual dysfunctions. To further improve the potency and selectivity of MC4R (ant)agonist peptide ligands, we designed and synthesized a series of cyclic peptides based on the recent crystal structure of MC4R in complex with the well-characterized antagonist (Ac-Nle-c[Asp-His-DNal(2')-Arg-Trp-Lys]-NH).

Optimized Opioid-Neurotensin Multitarget Peptides: From Design to Structure-Activity Relationship Studies.

Fusion of nonopioid pharmacophores, such as neurotensin, with opioid ligands represents an attractive approach for pain treatment. Herein, the μ-/δ-opioid agonist tetrapeptide H-Dmt-d-Arg-Aba-β-Ala-NH () was fused to analogues. Since the NTS1 receptor has been linked to adverse effects, selective MOR-NTS2 ligands are preferred.

Neurotensin Analogues Containing Cyclic Surrogates of Tyrosine at Position 11 Improve NTS2 Selectivity Leading to Analgesia without Hypotension and Hypothermia.

Neurotensin (NT) exerts its analgesic effects through activation of the G protein-coupled receptors NTS1 and NTS2. This opioid-independent antinociception represents a potential alternative for pain management. While activation of NTS1 also induces a drop in blood pressure and body temperature, NTS2 appears to be an analgesic target free of these adverse effects.

Neuromedin U and Structural Analogs: An Overview of their Structure, Function and Selectivity.

The neuromedin U peptide sequence is highly conserved between various species. Neuromedin U is involved in a variety of physiological processes. It exerts its effects via two neuromedin U receptors, NMUR1 and NMUR2.

Trifluoromethylated Proline Surrogates as Part of "Pro-Pro" Turn-Inducing Templates.

Proline is often found as a turn inducer in peptide or protein domains. Exploitation of its restricted conformational freedom led to the development of the d-Pro-l-Pro (corresponding to (R)-Pro-(S)-Pro) segment as a "templating" unit, frequently used in the design of β-hairpin peptidomimetics, in which conformational stability is, however, inherently linked to the cis-trans isomerization of the prolyl amide bonds. In this context, the stereoelectronic properties of the CF group can aid in conformational control.

Synthesis and Evaluation of Stabilized and Selective Neuromedin U-1 Receptor Agonists.

Neuromedin U (NMU) is a multifunctional neuropeptide which is characterized by a high conservation through all species. Herein, we describe the synthesis of a novel set of NMU-analogs based on the truncated NMU-8. Through combination of previously reported modifications, an elaborate structure-activity relationship study was performed aiming for the development of peptides with an increased selectivity toward NMU receptor 1 (NMUR1).

Rapid construction of substituted 3-amino-1,5-benzothiazepin-4(5H)-one dipeptide scaffolds through an Ugi-4CR - Ullmann cross-coupling sequence.

A 3-step methodology for the synthesis of 1,5-benzothiazepin-4(5H)-one dipeptidomimetics has been elaborated via an Ugi-4CR followed by a S-trityl deprotection and an intramolecular Cu(i)-catalyzed Ullmann condensation with moderate to good yields. In silico and NMR conformational studies showed that the lowest energy conformers stabilize γ- and β-turn structures.

Indoloazepinone-Constrained Oligomers as Cell-Penetrating and Blood-Brain-Barrier-Permeating Compounds.

Non-cationic and amphipathic indoloazepinone-constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l-Aia-Xxx] oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc-[l-Aia-Gly] -OBn oligomers 12 and 13 and Boc-[l-Aia-β -h-l-Ala] -OBn oligomers 16 and 17 were totally or partially disordered, Boc-[l-Aia-l-Ala] -OBn (14) induced a typical turn stabilized by C - and C -membered H-bond pseudo-cycles and aromatic interactions.

Development of potent and proteolytically stable human neuromedin U receptor agonists.

Neuromedin U (NMU) is a highly conserved endogenous peptide that is involved in a wide range of physiological processes such as regulation of feeding behavior, the stress response and nociception. The major limitation to use NMU as a therapeutic is its short half-life. Here, we describe the development of a set of novel NMU-analogs based on NMU-8, by introducing unnatural amino acids into the native sequence.

χ-Space Screening of Dermorphin-Based Tetrapeptides through Use of Constrained Arylazepinone and Quinolinone Scaffolds.

Herein, the synthesis of novel conformationally constrained amino acids, 4-amino-8-bromo-2-benzazepin-3-one (8-Br-Aba), 3-amino-3,4-dihydroquinolin-2-one, and regioisomeric 4-amino-naphthoazepinones (1- and 2-Ana), is described. Introduction of these constricted scaffolds into the -terminal tetrapeptide of dermorphin (i.e.

Efficient One-Pot Access to Trisubstituted 2-Benzazepin-3-ones as Constrained Pseudopeptide Analogues and Privileged Scaffolds.

Background: Benzazepines received great attention in the field of medicinal chemistry since this scaffold has been recognized to belong to the important family of privileged templates. More specifically, the 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) is used as a core structure in a variety of constrained therapeutic peptide (turn) mimetics.Most of the synthetic approaches towards this template have focused on cyclizations which form the central 7-membered azepine ring.

Hydrazone Linker as a Useful Tool for Preparing Chimeric Peptide/Nonpeptide Bifunctional Compounds.

The area of multitarget compounds, joining two pharmacophores within one molecule, is a vivid field of research in medicinal chemistry. Not only pharmacophoric elements are essential for the design and activity of such compounds, but the type and length of linkers used to connect them are also crucial. In the present contribution, we describe compound in which a typical opioid peptide sequence is combined with a fragment characteristic for neurokinin-1 receptor (NK1R) antagonists through a hydrazone bridge.

Side Chain Cyclized Aromatic Amino Acids: Great Tools as Local Constraints in Peptide and Peptidomimetic Design.

Constraining the conformation of flexible peptides is a proven strategy to increase potency, selectivity, and metabolic stability. The focus has mostly been on constraining the backbone dihedral angles; however, the correct orientation of the amino acid side chains (χ-space) that constitute the peptide pharmacophore is equally important. Control of χ-space utilizes conformationally constrained amino acids that favor, disfavor, or exclude the gauche (-), the gauche (+), or the trans conformation.

Efficient one-pot synthesis of amino-benzotriazolodiazocinone scaffolds via catalyst-free tandem Ugi-Huisgen reactions.

Herein we describe a catalyst-free, one-pot procedure employing an Ugi-4CR between propargyl glycine, functionalised 2-azidoanilines, different isocyanides and aldehydes, followed by a thermal azide-alkyne Huisgen cycloaddition to generate a 14-member set of amino-benzotriazolodiazocine-bearing dipeptides with multiple points of diversification and high atom economy. These structures were derivatized by means of Suzuki-Miyaura cross-coupling reactions at two positions with good to excellent yields, leading to conformationally constrained tricyclic structures. In silico and NMR conformational analysis studies demonstrated that turn conformations are adopted by these structures.

Bifunctional Peptide-Based Opioid Agonist-Nociceptin Antagonist Ligands for Dual Treatment of Acute and Neuropathic Pain.

Herein, the opioid pharmacophore H-Dmt-d-Arg-Aba-β-Ala-NH2 (7) was linked to peptide ligands for the nociceptin receptor. Combination of 7 and NOP ligands (e.g.

Dual Alleviation of Acute and Neuropathic Pain by Fused Opioid Agonist-Neurokinin 1 Antagonist Peptidomimetics.

Herein, the synthesis and biological evaluation of dual opioid agonists-neurokinin 1 receptor (NK1R) antagonists is described. In these multitarget ligands, the two pharmacophores do not overlap, and this allowed maintaining high NK1R affinity and antagonist potency in compounds 12 and 13. Although the fusion of the two ligands resulted in slightly diminished opioid agonism at the μ- and δ-opioid receptors (MOR and DOR, respectively), as compared to the opioid parent peptide, balanced MOR/DOR activities were obtained.

Synthesis and binding characteristics of [(3)H]neuromedin N, a NTS2 receptor ligand.

Neurotensin (NT) and its analog neuromedin N (NN) are formed by the processing of a common precursor in mammalian brain tissue and intestines. The biological effects mediated by NT and NN (e.g.

T3P-Promoted, Mild, One-Pot Syntheses of Constrained Polycyclic Lactam Dipeptide Analogues via Stereoselective Pictet-Spengler and Meyers Lactamization Reactions.

A new convenient, mild, one-pot procedure is described for the diastereoselective synthesis of constrained 7,5- and 7,6-fused azabicycloalkanes. Using 2-formyl-L-tryptophan and 2-formyl-l-phenylalanine as bielectrophilic building blocks, T3P-mediated Pictet-Spengler and Meyers lactamization reactions were developed to present chiral and polycyclic aminoindolo- and aminobenzazepinone compounds in excellent yields. The conformationally constrained compounds can serve as templates for peptidomimetic research or polyheterocyclic privileged scaffolds.

Oxidative α,ω-diyne coupling as an approach towards novel peptidic macrocycles.

The Glaser-Hay diyne coupling proved to be an efficient cyclisation approach towards diyne containing peptidic macrocycles. A variety of tetrapeptide-based macrocyclic 1,3-diynes were obtained from O-propargylated serine or tyrosine residues using Cu(OAc)2·H2O and NiCl2 under an O2-atmosphere. The effect of the linear 1,3-diyne on peptide conformations was studied by NMR and compared with a macrocycle bearing a saturated linker.