Design,Synthesis, and Biological Evaluation of 3‐Benzazepin‐1‐ols as NR2B‐Selective NMDA Receptor Antagonists

Cleavage and reconstitution of a bond in the piperidine ring of ifenprodil ( 1 ) leads to 7‐methoxy‐2,3,4,5‐tetrahydro‐1H‐3‐benzazepin‐1‐ols, a novel class of NR2B‐selective NMDA receptor antagonists. The secondary amine 7‐methoxy‐2,3,4,5‐tetrahydro‐1H‐3‐benzazepin‐1‐ol ( 12 ), which was synthesized in six steps starting from 2‐phenylethylamine 3 , represents the central building block for the introduction of several N‐linked residues. A distance of four methylene units between the basic nitrogen atom and the phenyl residue in the side chain results in high NR2B affinity. The 4‐phenylbutyl derivative 13 (WMS‐1405, K_i=5.4 nM ) and the conformationally restricted 4‐phenylcyclohexyl derivative 31 (K_i=10 nM ) represent the most potent NR2B ligands of this series. Whereas 13 shows excellent selectivity, the 4‐phenylcyclohexyl derivative 31 also interacts with σ₁ (K_i=33 nM ) and σ₂ receptors (K_i=82 nM ). In the excitotoxicity assay the phenylbutyl derivative 13 inhibits the glutamate‐induced cytotoxicity with an IC₅₀ value of 360 nM , indicating that 13 is an NMDA antagonist.     

Synthesis and Pharmacological Evaluation of Dimeric Follicle‐Stimulating Hormone Receptor Antagonists

A series of homo‐ and heterodimeric compounds encompassing the follicle‐stimulating hormone receptor (FSHR) antagonist (R)‐ 1 and its inactive conformer (S)‐ 1 connected through ethylene glycol spacers of various lengths is described. Evaluation of these compounds reveals that dimeric compounds, with a spacer of sufficient length, bearing two active copies of the antagonist are more potent relative to dimeric compounds in which one of the active pharmacophores is replaced by an inactive conformer. Interestingly, the opposite trend is observed if a short spacer is used, indicating that these compounds may be valuable tools to study FSHR dimerization in greater detail.     

MT1‐Selective Melatonin Receptor Ligands: Synthesis,Pharmacological Evaluation,and Molecular Dynamics Investigation of N‐{[(3‐O‐Substituted)anilino]alkyl}amides

The design of compounds selective for the MT₁ melatonin receptor is still a challenging task owing to the limited knowledge of the structural features conferring selectivity for the MT₁ subtype, and only few selective compounds have been reported so far. N‐(Anilinoalkyl)amides are a versatile class of melatonin receptor ligands that include nonselective MT₁/MT₂ agonists and MT₂‐selective antagonists. We synthesized a new series of N‐(anilinoalkyl)amides bearing 3‐arylalkyloxy or 3‐alkyloxy substituents at the aniline ring, looking for new potent and MT₁‐selective ligands. To evaluate the effect of substituent size and shape on binding affinity and intrinsic activity, both flexible and conformationally constrained derivatives were prepared. The phenylbutyloxy substituent gave the best result, providing the partial agonist 4 a , which was endowed with high MT₁ binding affinity (pK_i=8.93) and 78‐fold selectivity for the MT₁ receptor. To investigate the molecular basis for agonist recognition, and to explain the role of the 3‐arylalkyloxy substituent, we built a homology model of the MT₁ receptor based on the β₂ adrenergic receptor crystal structure in its activated state. A binding mode for MT₁ agonists is proposed, as well as a hypothesis regarding the receptor structural features responsible for MT₁ selectivity of compounds with lipophilic arylalkyloxy substituents.     

Aryl Biphenyl‐3‐ylmethylpiperazines as 5‐HT7 Receptor Antagonists

The 5‐HT₇ receptor (5‐HT₇R) is a promising therapeutic target for the treatment of depression and neuropathic pain. The 5‐HT₇R antagonist SB‐269970 exhibited antidepressant‐like activity, whereas systemic administration of the 5‐HT₇R agonist AS‐19 significantly inhibited mechanical hypersensitivity and thermal hyperalgesia. In our efforts to discover selective 5‐HT₇R antagonists or agonists, aryl biphenyl‐3‐ylmethylpiperazines were designed, synthesized, and biologically evaluated against the 5‐HT₇R. Among the synthesized compounds, 1‐([2′‐methoxy‐(1,1′‐biphenyl)‐3‐yl]methyl)‐4‐(2‐methoxyphenyl)piperazine ( 28 ) was the best binder to the 5‐HT₇R (pK_i=7.83), and its antagonistic property was confirmed by functional assays. The selectivity profile of compound 28 was also recorded for the 5‐HT₇R over other serotonin receptor subtypes, such as 5‐HT₁R, 5‐HT₂R, 5‐HT₃R, and 5‐HT₆R. In a molecular modeling study, the 2‐methoxyphenyl moiety attached to the piperazine ring of compound 28 was proposed to be essential for the antagonistic function.     

Evaluation of (4‐Arylpiperidin‐1‐yl)cyclopentanecarboxamides As High‐Affinity and Long‐Residence‐Time Antagonists for the CCR2 Receptor

Animal models suggest that the chemokine ligand 2/CC‐chemokine receptor 2 (CCL2/CCR2) axis plays an important role in the development of inflammatory diseases. However, CCR2 antagonists have failed in clinical trials because of a lack of efficacy. We previously described a new approach for the design of CCR2 antagonists by the use of structure–kinetics relationships (SKRs). Herein we report new findings on the structure–affinity relationships (SARs) and SKRs of the reference compound MK‐0483, its diastereomers, and its structural analogues as CCR2 antagonists. The SARs of the 4‐arylpiperidine group suggest that lipophilic hydrogen‐bond‐accepting substituents at the 3‐position are favorable. However, the SKRs suggest that a lipophilic group with a certain size is desired [e.g., 3‐Br: K_i=2.8 nM , residence time (t_res)=243 min; 3‐iPr: K_i=3.6 nM , t_res=266 min]. Alternatively, additional substituents and further optimization of the molecule, while keeping a carboxylic acid at the 3‐position, can also prolong t_res; this was most prominently observed in MK‐0483 (K_i=1.2 nM , t_res=724 min) and a close analogue (K_i=7.8 nM ) with a short residence time.     

Synthesis,Structure–Activity Relationship Studies,and ADMET Properties of 3‐Aminocyclohex‐2‐en‐1‐ones as Chemokine Receptor 2 (CXCR2) Antagonists

Herein we describe the synthesis and structure–activity relationships of 3‐aminocyclohex‐2‐en‐1‐one derivatives as novel chemokine receptor 2 (CXCR2) antagonists. Thirteen out of 44 derivatives were found to inhibit CXCR2 downstream signaling in a Tango assay specific for CXCR2, with IC₅₀ values less than 10 μm . In silico ADMET prediction suggests that all active compounds possess drug‐like properties. None of these compounds show significant cytotoxicity, suggesting their potential application in inflammatory mediated diseases. A structure–activity relationship (SAR) map has been generated to gain better understanding of their binding mechanism to guide further optimization of these new CXCR2 antagonists.     

Synthesis,SAR and Unanticipated Pharmacological Profiles of Analogues of the mGluR5 Ago‐potentiator ADX‐47273

An iterative analogue library synthesis strategy rapidly developed comprehensive SAR for the mGluR5 ago‐potentiator ADX‐47273. This effort identified key substituents in the 3‐position of oxadiazole that engendered either mGluR5 ago‐potentiation or pure mGluR5 positive allosteric modulation. The mGluR5 positive allosteric modulators identified possessed the largest fold shifts (up to 27.9‐fold) of the glutamate CRC reported to date as well as providing improved physiochemical properties.

     

Synthesis and Pharmacological Evaluation of α4β2 Nicotinic Ligands with a 3‐Fluoropyrrolidine Nucleus

Nicotinic acetylcholine receptors (nAChRs) play an important role in many central nervous system disorders such as Alzheimer’s and Parkinson’s diseases, schizophrenia, and mood disorders. The α₄β₂ subtype has emerged as an important target for the early diagnosis and amelioration of Alzheimer’s disease symptoms. Herein we report a new class of α₄β₂ receptor ligands characterized by a basic pyrrolidine nucleus, the basicity of which was properly decreased through the insertion of a fluorine atom at the 3‐position, and a pyridine ring carrying at the 3‐position substituents known to positively affect affinity and selectivity toward the α₄β₂ subtype. Derivatives 3‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)‐5‐(phenylethynyl)pyridine ( 11 ) and 3‐((4‐fluorophenyl)ethynyl)‐5‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)pyridine ( 12 ) were found to be the most promising ligands identified in this study, showing good affinity and selectivity for the α₄β₂ subtype and physicochemical properties predictive of a relevant central nervous system penetration.     

(2,2‐Diphenyl‐[1,3]oxathiolan‐5‐ylmethyl)‐(3‐phenyl‐propyl)‐amine: a Potent and Selective 5‐HT1A Receptor Agonist

A selective 5‐HT _1A receptor agonist : A new series of ligands acting at 5‐HT_1A serotonin receptor were identified. Among them (2,2‐diphenyl‐[1,3]oxathiolan‐5‐yl‐methyl)‐(3‐phenyl‐propyl)amine (shown) possesses outstanding activity (pK_i=8.72, pD₂=7.67, E_max=85) and selectivity (5‐HT_1A/α_1D>150), and represents a new 5‐HT_1A agonist chemotype.

     

GluN2B‐Selective N‐Methyl‐d‐aspartate (NMDA) Receptor Antagonists Derived from 3‐Benzazepines: Synthesis and Pharmacological Evaluation of Benzo[7]annulen‐7‐amines

Given their high neuroprotective potential, ligands that block GluN2B‐containing N‐methyl‐D ‐aspartate (NMDA) receptors by interacting with the ifenprodil binding site located on the GluN2B subunit are of great interest for the treatment of various neuronal disorders. In this study, a novel class of GluN2B‐selective NMDA receptor antagonists with the benzo[7]annulene scaffold was prepared and pharmacologically evaluated. The key intermediate, N‐(2‐methoxy‐5‐oxo‐6,7,8,9‐tetrahydro‐5H‐benzo[7]annulen‐7‐yl)acetamide ( 11 ), was obtained by cyclization of 3‐acetamido‐5‐(3‐methoxyphenyl)pentanoic acid ( 10 b ). The final reaction steps comprise hydrolysis of the amide, reduction of the ketone, and reductive alkylation, leading to cis‐ and trans‐configured 7‐(ω‐phenylalkylamino)benzo[7]annulen‐5‐ols. High GluN2B affinity was observed with cis‐configured γ‐amino alcohols substituted with a 3‐phenylpropyl moiety at the amino group. Removal of the benzylic hydroxy moiety led to the most potent GluN2B antagonists of this series: 2‐methoxy‐N‐(3‐phenylpropyl)‐6,7,8,9‐tetrahydro‐5H‐benzo[7]annulen‐7‐amine ( 20 a , K_i=10 nM ) and 2‐methoxy‐N‐methyl‐N‐(3‐phenylpropyl)‐6,7,8,9‐tetrahydro‐5H‐benzo[7]annulen‐7‐amine ( 23 a , K_i=7.9 nM ). The selectivity over related receptors (phencyclidine binding site of the NMDA receptor, σ₁ and σ₂ receptors) was recorded. In a functional assay measuring the cytoprotective activity of the benzo[7]annulenamines, all tested compounds showed potent NMDA receptor antagonistic activity. Cytotoxicity induced via GluN2A subunit‐containing NMDA receptors was not inhibited by the new ligands.     

Discovery of α‐Substituted Imidazole‐4‐acetic Acid Analogues as a Novel Class of ρ1 γ‐Aminobutyric Acid Type A Receptor Antagonists with Effect on Retinal Vascular Tone

The ρ‐containing γ‐aminobutyric acid type A receptors (GABA_ARs) play an important role in controlling visual signaling. Therefore, ligands that selectively target these GABA_ARs are of interest. In this study, we demonstrate that the partial GABA_AR agonist imidazole‐4‐acetic acid (IAA) is able to penetrate the blood–brain barrier in vivo; we prepared a series of α‐ and N‐alkylated, as well as bicyclic analogues of IAA to explore the structure–activity relationship of this scaffold focusing on the acetic acid side chain of IAA. The compounds were prepared via IAA from l ‐histidine by an efficient minimal‐step synthesis, and their pharmacological properties were characterized at native rat GABA_ARs in a [³H]muscimol binding assay and at recombinant human α₁β₂γ_2S and ρ₁ GABA_ARs using the FLIPR? membrane potential assay. The (+)‐α‐methyl‐ and α‐cyclopropyl‐substituted IAA analogues ((+)‐ 6 a and 6 c , respectively) were identified as fairly potent antagonists of the ρ₁ GABA_AR that also displayed significant selectivity for this receptor over the α₁β₂γ_2S GABA_AR. Both 6 a and 6 c were shown to inhibit GABA‐induced relaxation of retinal arterioles from porcine eyes.     

Synthesis and Biological Characterization of (3R,4R)‐4‐(2‐(Benzhydryloxy)ethyl)‐1‐((R)‐2‐hydroxy‐2‐phenylethyl)‐piperidin‐3‐ol and Its Stereoisomers for Activity toward Monoamine Transporters

A novel series of optically active molecules based on a 4‐(2‐(benzhydryloxy)ethyl)‐1‐((R)‐2‐hydroxy‐2‐phenylethyl)‐piperidin‐3‐ol template were developed. Depending on stereochemistry, the compounds exhibit various degrees of affinity for three dopamine, serotonin, and norepinephrine transporters. These molecules have the potential for treating several neurological disorders such as drug abuse, depression, and attention deficit hyperactivity disorder.

     

Synthesis and Biological Evaluation of N‐Substituted Noscapine Analogues

Noscapine is a phthalideisoquinoline alkaloid isolated from the opium poppy Papaver somniferum. It has long been used as an antitussive agent, but has more recently been found to possess microtubule‐modulating properties and anticancer activity. Herein we report the synthesis and pharmacological evaluation of a series of 6′‐substituted noscapine derivatives. To underpin this structure–activity study, an efficient synthesis of N‐nornoscapine and its subsequent reduction to the cyclic ether derivative of N‐nornoscapine was developed. Reaction of the latter with a range of alkyl halides, acid chlorides, isocyanates, thioisocyanates, and chloroformate reagents resulted in the formation of the corresponding N‐alkyl, N‐acyl, N‐carbamoyl, N‐thiocarbamoyl, and N‐carbamate derivatives, respectively. The ability of these compounds to inhibit cell proliferation was assessed in cell‐cycle cytotoxicity assays using prostate cancer (PC3), breast cancer (MCF‐7), and colon cancer (Caco‐2) cell lines. Compounds that showed activity in the cell‐cycle assay were further evaluated in cell viability assays using PC3 and MCF‐7 cells.     

Synthesis and Structure–Activity Relationships of 1‐Benzyl‐4,5,6‐trimethoxyindoles as a Novel Class of Potent Antimitotic Agents

Combretastatin A‐4 derivatives : A series of combretastatin A‐4‐derived 1‐benzyl‐4,5,6‐trimethoxyindoles was designed and prepared as a novel class of potent antimitotic agents acting through the colchicine binding site on the microtubule.

     

Synthesis of N‐Substituted Iminosugar Derivatives and Evaluation of Their Immunosuppressive Activities

It is important to find more effective and safer immunosuppressants, because clinically used immunosuppressive agents have significant side effects. A series of N‐substituted iminosugar derivatives were designed and synthesized, and their immunosuppressive effects were evaluated by the CCK‐8 assay. The results revealed that iminosugars 10 e and 10 i , that is, (3R,4S)‐1‐(4‐heptyloxylphenylethyl)pyrrolidine‐3,4‐diol and (3R,4S)‐1‐[2‐(2‐chloro‐4‐(p‐tolylthio)‐phenyl‐1‐yl)ethyl]pyrrolidine‐3,4‐diol, respectively, exhibited the strongest inhibitory effects on mouse splenocyte proliferation (IC₅₀=2.16 and 2.48 μm , respectively), whereas the iminosugars containing an amide group near the hydrophilic head (compounds 10 j – n ) exhibited no inhibitory effects. Further studies revealed that the inhibitory effects on splenocyte proliferation may have come from the suppression of both IFN‐γ and IL‐4 cytokines. Our results suggest that synthetic iminosugars, especially compounds 10 e and 10 i , hold potential as immunosuppressive agents.     

Synthesis and Biological Evaluation of N‐Substituted Sophocarpinic Acid Derivatives as Coxsackievirus B3 Inhibitors

A series of novel N‐substituted sophocarpinic acid derivatives was designed, synthesized, and evaluated for their anti‐enteroviral activities against coxsackievirus type B3 (CVB3) and coxsackievirus type B6 (CVB6) in Vero cells. Structure–activity relationship analysis revealed that the introduction of a benzenesulfonyl moiety on the 12‐nitrogen atom in (E)‐β,γ‐sophocarpinic acid might significantly enhance anti‐CVB3 activity. Among the derivatives, (E)‐12‐N‐(m‐cyanobenzenesulfonyl)‐β,γ‐sophocarpinic acid ( 11 m ), possessing a meta‐cyanobenzenesulfonyl group, exhibited potent activity against CVB3 with a selectivity index (SI) of 107. Furthermore, compound 11 m also showed a good oral pharmacokinetic profile, with an AUC value of 7.29 μM h^?1 in rats, and good safety through the oral route in mice, with an LD₅₀ value of >1000 mg kg^?1; these values suggest a druggable characteristic. Therefore, compound 11 m was selected for further investigation as a promising CVB3 inhibitor. We consider (E)‐β,γ‐N‐(benzenesulfonyl)sophocarpinic acids to be a novel class of anti‐CVB3 agents.     

para‐Substituted 2‐Phenyl‐3,4‐dihydroquinazolin‐4‐ones As Potent and Selective Tankyrase Inhibitors

Human tankyrases are attractive drug targets, especially for the treatment of cancer. We identified a set of highly potent tankyrase inhibitors based on a 2‐phenyl‐3,4‐dihydroquinazolin‐4‐one scaffold. Substitutions at the para position of the scaffold′s phenyl group were evaluated as a strategy to increase potency and improve selectivity. The best compounds displayed single‐digit nanomolar potencies, and profiling against several human diphtheria‐toxin‐like ADP‐ribosyltransferases revealed that a subset of these compounds are highly selective tankyrase inhibitors. The compounds also effectively inhibit Wnt signaling in HEK293 cells. The binding mode of all inhibitors was studied by protein X‐ray crystallography. This allowed us to establish a structural basis for the development of highly potent and selective tankyrase inhibitors based on the 2‐phenyl‐3,4‐dihydroquinazolin‐4‐one scaffold and outline a rational approach to the modification of other inhibitor scaffolds that bind to the nicotinamide site of the catalytic domain.     

5‐(Piperidin‐4‐yl)‐3‐Hydroxypyrazole: A Novel Scaffold for Probing the Orthosteric γ‐Aminobutyric Acid Type A Receptor Binding Site

A series of bioisosteric N₁‐ and N₂‐substituted 5‐(piperidin‐4‐yl)‐3‐hydroxypyrazole analogues of the partial GABA_AR agonists 4‐PIOL and 4‐PHP have been designed, synthesized, and characterized pharmacologically. The unsubstituted 3‐hydroxypyrazole analogue of 4‐PIOL ( 2 a ; IC₅₀～300 μM ) is a weak antagonist at the α₁β₂γ₂ GABA_AR, whereas substituting the N₁‐ or N₂‐position with alkyl or aryl substituents resulted in antagonists with binding affinities in the high nanomolar to low micromolar range at native rat GABA_ARs. Docking studies using a α₁β₂γ₂ GABA_AR homology model along with the obtained SAR indicate that the N₁‐substituted analogues of 4‐PIOL and 4‐PHP, 2 a – k , and previously reported 3‐substituted 4‐PHP analogues share a common binding mode to the orthosteric binding site in the receptor. Interestingly, the core scaffold of the N₂‐substituted analogues of 4‐PIOL and 4‐PHP, 3 b – k , are suggested to flip 180° thereby adapting to the binding pocket and addressing a cavity situated above the core scaffold.