1
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Wesseling CMJ, Slingerland CJ, Veraar S, Lok S, Martin NI. Structure-Activity Studies with Bis-Amidines That Potentiate Gram-Positive Specific Antibiotics against Gram-Negative Pathogens. ACS Infect Dis 2021; 7:3314-3335. [PMID: 34766746 PMCID: PMC8669655 DOI: 10.1021/acsinfecdis.1c00466] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
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Pentamidine, an FDA-approved
antiparasitic drug, was recently identified
as an outer membrane disrupting synergist that potentiates erythromycin,
rifampicin, and novobiocin against Gram-negative bacteria. The same
study also described a preliminary structure–activity relationship
using commercially available pentamidine analogues. We here report
the design, synthesis, and evaluation of a broader panel of bis-amidines
inspired by pentamidine. The present study both validates the previously
observed synergistic activity reported for pentamidine, while further
assessing the capacity for structurally similar bis-amidines to also
potentiate Gram-positive specific antibiotics against Gram-negative
pathogens. Among the bis-amidines prepared, a number of them were
found to exhibit synergistic activity greater than pentamidine. These
synergists were shown to effectively potentiate the activity of Gram-positive
specific antibiotics against multiple Gram-negative pathogens such
as Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas
aeruginosa, and Escherichia coli, including polymyxin- and carbapenem-resistant strains.
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Affiliation(s)
- Charlotte M. J. Wesseling
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, 2333 BE Leiden, The Netherlands
| | - Cornelis J. Slingerland
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, 2333 BE Leiden, The Netherlands
| | - Shanice Veraar
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, 2333 BE Leiden, The Netherlands
| | - Samantha Lok
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, 2333 BE Leiden, The Netherlands
| | - Nathaniel I. Martin
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, 2333 BE Leiden, The Netherlands
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2
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Cinelli MA, Reidl CT, Li H, Chreifi G, Poulos TL, Silverman RB. First Contact: 7-Phenyl-2-Aminoquinolines, Potent and Selective Neuronal Nitric Oxide Synthase Inhibitors That Target an Isoform-Specific Aspartate. J Med Chem 2020; 63:4528-4554. [PMID: 32302123 DOI: 10.1021/acs.jmedchem.9b01573] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Inhibition of neuronal nitric oxide synthase (nNOS), an enzyme implicated in neurodegenerative disorders, is an attractive strategy for treating or preventing these diseases. We previously developed several classes of 2-aminoquinoline-based nNOS inhibitors, but these compounds had drawbacks including off-target promiscuity, low activity against human nNOS, and only modest selectivity for nNOS over related enzymes. In this study, we synthesized new nNOS inhibitors based on 7-phenyl-2-aminoquinoline and assayed them against rat and human nNOS, human eNOS, and murine and (in some cases) human iNOS. Compounds with a meta-relationship between the aminoquinoline and a positively charged tail moiety were potent and had up to nearly 900-fold selectivity for human nNOS over human eNOS. X-ray crystallography indicates that the amino groups of some compounds occupy a water-filled pocket surrounding an nNOS-specific aspartate residue (absent in eNOS). This interaction was confirmed by mutagenesis studies, making 7-phenyl-2-aminoquinolines the first aminoquinolines to interact with this residue.
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Affiliation(s)
- Maris A Cinelli
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Cory T Reidl
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Georges Chreifi
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Thomas L Poulos
- Department of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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3
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Mittal A, Kakkar R. Nitric Oxide Synthases and Their Inhibitors: A Review. LETT DRUG DES DISCOV 2020. [DOI: 10.2174/1570180816666190222154457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric Oxide (NO), an important biological mediator, is involved in the regulation of the cardiovascular, nervous and immune systems in mammals. Synthesis of NO is catalyzed by its biosynthetic enzyme, Nitric Oxide Synthase (NOS). There are three main isoforms of the enzyme, neuronal NOS, endothelial NOS and inducible NOS, which have very similar structures but differ in their expression and activities. NO is produced in the active site of the enzyme in two distinct cycles from oxidation of the substrate L-arg (L-arginine) in nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reaction. NOS has gained considerable attention of biochemists due to its complexity and unique catalytic mechanism. The review focuses on NOS structure, its function and catalytic reaction mechanism. In particular, the review is concluded with a discussion on the role of all three isoforms of NOS in physiological and pathological conditions and their inhibitors with a focus on the role of computational techniques in their development.
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Affiliation(s)
- Anshika Mittal
- Computational Chemistry Laboratory, Department of Chemistry, University of Delhi, Delhi-110007, India
| | - Rita Kakkar
- Computational Chemistry Laboratory, Department of Chemistry, University of Delhi, Delhi-110007, India
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4
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Smolobochkin AV, Gazizov AS, Burilov AR, Pudovik MA, Sinyashin OG. Ring opening reactions of nitrogen heterocycles. RUSSIAN CHEMICAL REVIEWS 2019. [DOI: 10.1070/rcr4891] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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5
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Meng C, Xu J, Tang Y, Ai Y, Li F. The α-alkylation of ketones with alcohols in pure water catalyzed by a water-soluble Cp*Ir complex bearing a functional ligand. NEW J CHEM 2019. [DOI: 10.1039/c9nj03345a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A water-soluble dinuclear Cp*Ir complex bearing 4,4′,6,6′-tetrahydroxy-2,2′-bipyrimidine as a bridging ligand was found to be a highly effective catalyst for the α-alkylation of ketones with alcohols in water.
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Affiliation(s)
- Chong Meng
- School of Chemical Engineering
- Nanjing University of Science & Technology
- Nanjing 210094
- P. R. China
| | - Jing Xu
- School of Chemical Engineering
- Nanjing University of Science & Technology
- Nanjing 210094
- P. R. China
| | - Yawen Tang
- School of Chemical Engineering
- Nanjing University of Science & Technology
- Nanjing 210094
- P. R. China
| | - Yao Ai
- School of Chemical Engineering
- Nanjing University of Science & Technology
- Nanjing 210094
- P. R. China
| | - Feng Li
- School of Chemical Engineering
- Nanjing University of Science & Technology
- Nanjing 210094
- P. R. China
- State Key Laboratory of Fine Chemicals
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6
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Serafim RAM, Pernichelle FG, Ferreira EI. The latest advances in the discovery of nitric oxide hybrid drug compounds. Expert Opin Drug Discov 2017; 12:941-953. [PMID: 28664751 DOI: 10.1080/17460441.2017.1344400] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
INTRODUCTION There is a great interest in Nitric oxide (NO) within medicinal chemistry since it's involved in human signaling pathways. Prodrugs or hybrid compounds containing NO-donor scaffolds linked to an active compound are valuable, due to their potential for modulating many pathological conditions due to NO's biological properties when released in addition to the native drug. Compounds that selectively inhibit nitric oxide synthase isoforms (NOS) can also increase therapeutic capacity, particularly in the treatment of chronic diseases. However, search for bioactive compounds to efficiently and selectively modulate NO is still a challenge in drug discovery. Areas covered: In this review, the authors highlight the recent advances in the strategies used to discover NO-hybrid derivatives, especially those related to anti-inflammatory, cardiovascular, anticancer and anti-microorganism activities. They also focus on: nitric oxide synthase inhibitors, NO delivery materials and other related activities. Expert opinion: The process of molecular hybridization can be used to obtain NO-releasing compounds that also interact with different targets. The main problem with this approach is to control NO multiple actions in the right biological system. However, the use of NO-releasing groups with many different scaffolds leads to new molecular structures for bioactive compounds, suggesting synergies.
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Affiliation(s)
- Ricardo A M Serafim
- a LAPEN: Laboratory of Design and Synthesis of Chemotherapeutic Potentially Active against Neglected Diseases, Department of Pharmacy, Faculty of Pharmaceutical Sciences , University of São Paulo - FCF/USP , São Paulo , Brazil
| | - Filipe G Pernichelle
- a LAPEN: Laboratory of Design and Synthesis of Chemotherapeutic Potentially Active against Neglected Diseases, Department of Pharmacy, Faculty of Pharmaceutical Sciences , University of São Paulo - FCF/USP , São Paulo , Brazil
| | - Elizabeth I Ferreira
- a LAPEN: Laboratory of Design and Synthesis of Chemotherapeutic Potentially Active against Neglected Diseases, Department of Pharmacy, Faculty of Pharmaceutical Sciences , University of São Paulo - FCF/USP , São Paulo , Brazil
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7
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Cinelli MA, Li H, Chreifi G, Poulos TL, Silverman RB. Nitrile in the Hole: Discovery of a Small Auxiliary Pocket in Neuronal Nitric Oxide Synthase Leading to the Development of Potent and Selective 2-Aminoquinoline Inhibitors. J Med Chem 2017; 60:3958-3978. [PMID: 28422508 PMCID: PMC5567828 DOI: 10.1021/acs.jmedchem.7b00259] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Neuronal nitric oxide synthase (nNOS) inhibition is a promising strategy to treat neurodegenerative disorders, but the development of nNOS inhibitors is often hindered by poor pharmacokinetics. We previously developed a class of membrane-permeable 2-aminoquinoline inhibitors and later rearranged the scaffold to decrease off-target binding. However, the resulting compounds had decreased permeability, low human nNOS activity, and low selectivity versus human eNOS. In this study, 5-substituted phenyl ether-linked aminoquinolines and derivatives were synthesized and assayed against purified NOS isoforms. 5-Cyano compounds are especially potent and selective rat and human nNOS inhibitors. Activity and selectivity are mediated by the binding of the cyano group to a new auxiliary pocket in nNOS. Potency was enhanced by methylation of the quinoline and by introduction of simple chiral moieties, resulting in a combination of hydrophobic and auxiliary pocket effects that yielded high (∼500-fold) n/e selectivity. Importantly, the Caco-2 assay also revealed improved membrane permeability over previous compounds.
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Affiliation(s)
- Maris A. Cinelli
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Georges Chreifi
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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8
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Liu P, Liang R, Lu L, Yu Z, Li F. Use of a Cyclometalated Iridium(III) Complex Containing a N∧C∧N-Coordinating Terdentate Ligand as a Catalyst for the α-Alkylation of Ketones and N-Alkylation of Amines with Alcohols. J Org Chem 2017; 82:1943-1950. [DOI: 10.1021/acs.joc.6b02758] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Pengcheng Liu
- School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, People’s Republic of China
| | - Ran Liang
- School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, People’s Republic of China
| | - Lei Lu
- School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, People’s Republic of China
| | - Zhentao Yu
- Jiangsu
Key Laboratory for Nano Technology, College of Engineering and Applied
Science, Nanjing University, Nanjing 210093, People’s Republic of China
| | - Feng Li
- School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, People’s Republic of China
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9
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The "Sticky Patch" Model of Crystallization and Modification of Proteins for Enhanced Crystallizability. Methods Mol Biol 2017; 1607:77-115. [PMID: 28573570 DOI: 10.1007/978-1-4939-7000-1_4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Crystallization of macromolecules has long been perceived as a stochastic process, which cannot be predicted or controlled. This is consistent with another popular notion that the interactions of molecules within the crystal, i.e., crystal contacts, are essentially random and devoid of specific physicochemical features. In contrast, functionally relevant surfaces, such as oligomerization interfaces and specific protein-protein interaction sites, are under evolutionary pressures so their amino acid composition, structure, and topology are distinct. However, current theoretical and experimental studies are significantly changing our understanding of the nature of crystallization. The increasingly popular "sticky patch" model, derived from soft matter physics, describes crystallization as a process driven by interactions between select, specific surface patches, with properties thermodynamically favorable for cohesive interactions. Independent support for this model comes from various sources including structural studies and bioinformatics. Proteins that are recalcitrant to crystallization can be modified for enhanced crystallizability through chemical or mutational modification of their surface to effectively engineer "sticky patches" which would drive crystallization. Here, we discuss the current state of knowledge of the relationship between the microscopic properties of the target macromolecule and its crystallizability, focusing on the "sticky patch" model. We discuss state-of-the-art in silico methods that evaluate the propensity of a given target protein to form crystals based on these relationships, with the objective to design variants with modified molecular surface properties and enhanced crystallization propensity. We illustrate this discussion with specific cases where these approaches allowed to generate crystals suitable for structural analysis.
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10
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Wang HY, Qin Y, Li H, Roman LJ, Martásek P, Poulos TL, Silverman RB. Potent and Selective Human Neuronal Nitric Oxide Synthase Inhibition by Optimization of the 2-Aminopyridine-Based Scaffold with a Pyridine Linker. J Med Chem 2016; 59:4913-25. [PMID: 27050842 DOI: 10.1021/acs.jmedchem.6b00273] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Neuronal nitric oxide synthase (nNOS) is an important therapeutic target for the treatment of various neurodegenerative disorders. A major challenge in the design of nNOS inhibitors focuses on potency in humans and selectivity over other NOS isoforms. Here we report potent and selective human nNOS inhibitors based on the 2-aminopyridine scaffold with a central pyridine linker. Compound 14j, the most promising inhibitor in this study, exhibits excellent potency for rat nNOS (Ki = 16 nM) with 828-fold n/e and 118-fold n/i selectivity with a Ki value of 13 nM against human nNOS with 1761-fold human n/e selectivity. Compound 14j also displayed good metabolic stability in human liver microsomes, low plasma protein binding, and minimal binding to cytochromes P450 (CYPs), although it had little to no Caco-2 permeability.
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Affiliation(s)
- Heng-Yen Wang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Yajuan Qin
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.,State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University , Nanjing 210093, People's Republic of China
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Linda J Roman
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States
| | - Pavel Martásek
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States.,Department of Pediatrics, First Faculty of Medicine, Charles University , 121 08 Prague, Czech Republic.,BIOCEV , 252 42 Vestec, Czech Republic
| | - Thomas L Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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11
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Holden JK, Kang S, Beasley FC, Cinelli MA, Li H, Roy SG, Dejam D, Edinger AL, Nizet V, Silverman RB, Poulos TL. Nitric Oxide Synthase as a Target for Methicillin-Resistant Staphylococcus aureus. ACTA ACUST UNITED AC 2016; 22:785-92. [PMID: 26091171 DOI: 10.1016/j.chembiol.2015.05.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 04/20/2015] [Accepted: 05/17/2015] [Indexed: 02/04/2023]
Abstract
Bacterial infections associated with methicillin-resistant Staphylococcus aureus (MRSA) are a major economic burden to hospitals, and confer high rates of morbidity and mortality among those infected. Exploitation of novel therapeutic targets is thus necessary to combat this dangerous pathogen. Here, we report on the identification and characterization, including crystal structures, of two nitric oxide synthase (NOS) inhibitors that function as antimicrobials against MRSA. These data provide the first evidence that bacterial NOS (bNOS) inhibitors can work synergistically with oxidative stress to enhance MRSA killing. Crystal structures show that each inhibitor contacts an active site Ile residue in bNOS that is Val in the mammalian NOS isoforms. Mutagenesis studies show that the additional nonpolar contacts provided by the Ile in bNOS contribute to tighter binding toward the bacterial enzyme.
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Affiliation(s)
- Jeffrey K Holden
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, CA 92697-3900, USA
| | - Soosung Kang
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208-3113, USA
| | - Federico C Beasley
- Departments of Pediatrics and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, CA 92093, USA
| | - Maris A Cinelli
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208-3113, USA
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, CA 92697-3900, USA
| | - Saurabh G Roy
- Department of Developmental and Cell Biology, University of California, Irvine, CA 92697, USA
| | - Dillon Dejam
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, CA 92697-3900, USA
| | - Aimee L Edinger
- Department of Developmental and Cell Biology, University of California, Irvine, CA 92697, USA
| | - Victor Nizet
- Departments of Pediatrics and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, CA 92093, USA
| | - Richard B Silverman
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, IL 60208-3113, USA.
| | - Thomas L Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, CA 92697-3900, USA.
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12
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Cinelli MA, Li H, Pensa AV, Kang S, Roman LJ, Martásek P, Poulos TL, Silverman RB. Phenyl Ether- and Aniline-Containing 2-Aminoquinolines as Potent and Selective Inhibitors of Neuronal Nitric Oxide Synthase. J Med Chem 2015; 58:8694-712. [PMID: 26469213 DOI: 10.1021/acs.jmedchem.5b01330] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Excess nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) is implicated in neurodegenerative disorders. As a result, inhibition of nNOS and reduction of NO levels is desirable therapeutically, but many nNOS inhibitors are poorly bioavailable. Promising members of our previously reported 2-aminoquinoline class of nNOS inhibitors, although orally bioavailable and brain-penetrant, suffer from unfavorable off-target binding to other CNS receptors, and they resemble known promiscuous binders. Rearranged phenyl ether- and aniline-linked 2-aminoquinoline derivatives were therefore designed to (a) disrupt the promiscuous binding pharmacophore and diminish off-target interactions and (b) preserve potency, isoform selectivity, and cell permeability. A series of these compounds was synthesized and tested against purified nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) enzymes. One compound, 20, displayed high potency, selectivity, and good human nNOS inhibition, and retained some permeability in a Caco-2 assay. Most promisingly, CNS receptor counterscreening revealed that this rearranged scaffold significantly reduces off-target binding.
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Affiliation(s)
- Maris A Cinelli
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Anthony V Pensa
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Soosung Kang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Linda J Roman
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States
| | - Pavel Martásek
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States.,Department of Pediatrics, First Faculty of Medicine, Charles University , Prague, Czech Republic.,BIOCEV , Prague, Czech Republic
| | - Thomas L Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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13
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Kang S, Li H, Tang W, Martásek P, Roman LJ, Poulos TL, Silverman RB. 2-Aminopyridines with a Truncated Side Chain To Improve Human Neuronal Nitric Oxide Synthase Inhibitory Potency and Selectivity. J Med Chem 2015; 58:5548-60. [PMID: 26120733 PMCID: PMC4514563 DOI: 10.1021/acs.jmedchem.5b00573] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have analyzed a recently obtained crystal structure of human neuronal nitric oxide synthase (nNOS) and then designed and synthesized several 2-aminopyridine derivatives containing a truncated side chain to avoid the hydrophobic pocket that differentiates human and rat nNOS in an attempt to explore alternative binding poses along the substrate access channel of human nNOS. Introduction of an N-methylethane-1,2-diamine side chain and conformational constraints such as benzonitrile and pyridine as the middle aromatic linker were sufficient to increase human and rat nNOS binding affinity and inducible and endothelial NOS selectivity. We found that 14b is a potent inhibitor; the binding modes with human and rat nNOS are unexpected, inducing side chain rotamer changes in Gln478 (rat) at the top of the active site. Compound 19c exhibits Ki values of 24 and 55 nM for rat and human nNOS, respectively, with 153-fold iNOS and 1040-fold eNOS selectivity. 19c has 18% oral bioavailability.
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Affiliation(s)
- Soosung Kang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- New Drug Development Center, DGMIF, 80 Cheombok-ro, Dae-gu, Korea
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Wei Tang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Pavel Martásek
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78384-7760, United States
| | - Linda J. Roman
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78384-7760, United States
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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14
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Holden JK, Dejam D, Lewis MC, Huang H, Kang S, Jing Q, Xue F, Silverman RB, Poulos TL. Inhibitor Bound Crystal Structures of Bacterial Nitric Oxide Synthase. Biochemistry 2015; 54:4075-82. [PMID: 26062720 DOI: 10.1021/acs.biochem.5b00431] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitric oxide generated by bacterial nitric oxide synthase (NOS) increases the susceptibility of Gram-positive pathogens Staphylococcus aureus and Bacillus anthracis to oxidative stress, including antibiotic-induced oxidative stress. Not surprisingly, NOS inhibitors also improve the effectiveness of antimicrobials. Development of potent and selective bacterial NOS inhibitors is complicated by the high active site sequence and structural conservation shared with the mammalian NOS isoforms. To exploit bacterial NOS for the development of new therapeutics, recognition of alternative NOS surfaces and pharmacophores suitable for drug binding is required. Here, we report on a wide number of inhibitor-bound bacterial NOS crystal structures to identify several compounds that interact with surfaces unique to the bacterial NOS. Although binding studies indicate that these inhibitors weakly interact with the NOS active site, many of the inhibitors reported here provide a revised structural framework for the development of new antimicrobials that target bacterial NOS. In addition, mutagenesis studies reveal several key residues that unlock access to bacterial NOS surfaces that could provide the selectivity required to develop potent bacterial NOS inhibitors.
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Affiliation(s)
- Jeffrey K Holden
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Dillon Dejam
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew C Lewis
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - He Huang
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Soosung Kang
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Qing Jing
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Fengtian Xue
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Richard B Silverman
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Thomas L Poulos
- Departments of †Molecular Biology and Biochemistry, ‡Pharmaceutical Sciences, and §Chemistry, University of California, Irvine, California 92697-3900, United States.,∥Departments of Chemistry and Molecular Biosciences, ⊥Chemistry of Life Processes Institute, #Center for Molecular Innovation and Drug Discovery, Northwestern University, Evanston, Illinois 60208-3113, United States
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15
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Holden JK, Kang S, Hollingsworth SA, Li H, Lim N, Chen S, Huang H, Xue F, Tang W, Silverman RB, Poulos TL. Structure-based design of bacterial nitric oxide synthase inhibitors. J Med Chem 2015; 58:994-1004. [PMID: 25522110 PMCID: PMC4306518 DOI: 10.1021/jm501723p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
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Inhibition
of bacterial nitric oxide synthase (bNOS) has the potential to improve
the efficacy of antimicrobials used to treat infections by Gram-positive
pathogens Staphylococcus aureus and Bacillus anthracis. However, inhibitor specificity
toward bNOS over the mammalian NOS (mNOS) isoforms remains a challenge
because of the near identical NOS active sites. One key structural
difference between the NOS isoforms is the amino acid composition
of the pterin cofactor binding site that is adjacent to the NOS active
site. Previously, we demonstrated that a NOS inhibitor targeting both
the active and pterin sites was potent and functioned as an antimicrobial
(Holden, , Proc. Natl. Acad.
Sci. U.S.A.2013, 110, 1812724145412). Here we present additional crystal structures, binding
analyses, and bacterial killing studies of inhibitors that target
both the active and pterin sites of a bNOS and function as antimicrobials.
Together, these data provide a framework for continued development
of bNOS inhibitors, as each molecule represents an excellent chemical
scaffold for the design of isoform selective bNOS inhibitors.
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Affiliation(s)
- Jeffrey K Holden
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California , 2206 Nat. Sci. 1, Irvine, California 92697-3900, United States
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16
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Mukherjee P, Li H, Sevrioukova I, Chreifi G, Martásek P, Roman LJ, Poulos TL, Silverman RB. Novel 2,4-disubstituted pyrimidines as potent, selective, and cell-permeable inhibitors of neuronal nitric oxide synthase. J Med Chem 2014; 58:1067-88. [PMID: 25489882 PMCID: PMC4329833 DOI: 10.1021/jm501719e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Selective inhibition of neuronal nitric oxide synthase (nNOS) is an important therapeutic approach to target neurodegenerative disorders. However, the majority of the nNOS inhibitors developed are arginine mimetics and, therefore, suffer from poor bioavailability. We designed a novel strategy to combine a more pharmacokinetically favorable 2-imidazolylpyrimidine head with promising structural components from previous inhibitors. In conjunction with extensive structure-activity studies, several highly potent and selective inhibitors of nNOS were discovered. X-ray crystallographic analysis reveals that these type II inhibitors utilize the same hydrophobic pocket to gain strong inhibitory potency (13), as well as high isoform selectivity. Interestingly, select compounds from this series (9) showed good permeability and low efflux in a Caco-2 assay, suggesting potential oral bioavailability, and exhibited minimal off-target binding to 50 central nervous system receptors. Furthermore, even with heme-coordinating groups in the molecule, modifying other pharmacophoric fragments minimized undesirable inhibition of cytochrome P450s from human liver microsomes.
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Affiliation(s)
- Paramita Mukherjee
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , Evanston, Illinois 60208-3113, United States
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17
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Yang Y, Yu T, Lian YJ, Ma R, Yang S, Cho JY. Nitric oxide synthase inhibitors: a review of patents from 2011 to the present. Expert Opin Ther Pat 2014; 25:49-68. [PMID: 25380586 DOI: 10.1517/13543776.2014.979154] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Nitric oxide synthases (NOSs) are a family of enzymes that play an essential role in synthesizing nitric oxide (NO) by oxidizing l-arginine. As previously reported, NO is a significant mediator in cellular signaling pathways. It serves as a crucial regulator in insulin secretion, vascular tone, peristalsis, angiogenesis, neural development and inflammation. Due to its important role, the inhibition of these vital enzymes provides, as tools, the opportunity to gain an insight into potential therapeutic applications targeting NOSs. AREAS COVERED This paper reviews the patent literature between 2011 and mid-2014 that specified inhibitors of NOS family members as the significant targets. Google and Baidu search engines were used to find relevant patents and clinical information using NOSs or NOS inhibitor as search terms. EXPERT OPINION Considerable recent progress has been made in the development of NOS inhibitors with pharmacodynamic and pharmacokinetic properties, and such development is likely to continue. The patented compounds attenuated mostly embodying evidence from in vitro and in vivo trials that demonstrate good potential for future clinical human trials and industrial applications. Furthermore, new techniques such as X-ray ligand crystallographic study and structure-activity relationship were popularly utilized, which give new insights for developing novel, safe, efficient and selective NOS inhibitors.
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Affiliation(s)
- Yanyan Yang
- Institute for Translational Medicine, College of Medicine, Qingdao University , Qingdao 266021 , China
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18
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Mukherjee P, Cinelli MA, Kang S, Silverman RB. Development of nitric oxide synthase inhibitors for neurodegeneration and neuropathic pain. Chem Soc Rev 2014; 43:6814-38. [PMID: 24549364 PMCID: PMC4138306 DOI: 10.1039/c3cs60467e] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule in the human body, playing a crucial role in cell and neuronal communication, regulation of blood pressure, and in immune activation. However, overproduction of NO by the neuronal isoform of nitric oxide synthase (nNOS) is one of the fundamental causes underlying neurodegenerative disorders and neuropathic pain. Therefore, developing small molecules for selective inhibition of nNOS over related isoforms (eNOS and iNOS) is therapeutically desirable. The aims of this review focus on the regulation and dysregulation of NO signaling, the role of NO in neurodegeneration and pain, the structure and mechanism of nNOS, and the use of this information to design selective inhibitors of this enzyme. Structure-based drug design, the bioavailability and pharmacokinetics of these inhibitors, and extensive target validation through animal studies are addressed.
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Affiliation(s)
- Paramita Mukherjee
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
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19
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Huang H, Li H, Yang S, Chreifi G, Martásek P, Roman L, Meyskens FL, Poulos TL, Silverman RB. Potent and selective double-headed thiophene-2-carboximidamide inhibitors of neuronal nitric oxide synthase for the treatment of melanoma. J Med Chem 2014; 57:686-700. [PMID: 24447275 PMCID: PMC3983353 DOI: 10.1021/jm401252e] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Indexed: 01/10/2023]
Abstract
Selective inhibitors of neuronal nitric oxide synthase (nNOS) are regarded as valuable and powerful agents with therapeutic potential for the treatment of chronic neurodegenerative pathologies and human melanoma. Here, we describe a novel hybrid strategy that combines the pharmacokinetically promising thiophene-2-carboximidamide fragment and structural features of our previously reported potent and selective aminopyridine inhibitors. Two inhibitors, 13 and 14, show low nanomolar inhibitory potency (Ki = 5 nM for nNOS) and good isoform selectivities (nNOS over eNOS [440- and 540-fold, respectively] and over iNOS [260- and 340-fold, respectively]). The crystal structures of these nNOS-inhibitor complexes reveal a new hot spot that explains the selectivity of 14 and why converting the secondary to tertiary amine leads to enhanced selectivity. More importantly, these compounds are the first highly potent and selective nNOS inhibitory agents that exhibit excellent in vitro efficacy in melanoma cell lines.
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Affiliation(s)
- He Huang
- Department
of Chemistry, Department of Molecular Biosciences, Chemistry of Life
Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Sun Yang
- Chao
Family Comprehensive Cancer Center, University
of California, Irvine, California 92697-3900, United States
| | - Georges Chreifi
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Pavel Martásek
- Department
of Biochemistry, University of Texas Health
Science Center, San Antonio, Texas 78384-7760, United States
- Department
of Pediatrics and Center for Applied Genomics, First School of Medicine, Charles University, Prague, Czech Republic
| | - Linda
J. Roman
- Department
of Biochemistry, University of Texas Health
Science Center, San Antonio, Texas 78384-7760, United States
| | - Frank L. Meyskens
- Chao
Family Comprehensive Cancer Center, University
of California, Irvine, California 92697-3900, United States
| | - Thomas L. Poulos
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department
of Chemistry, Department of Molecular Biosciences, Chemistry of Life
Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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20
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Rochette L, Lorin J, Zeller M, Guilland JC, Lorgis L, Cottin Y, Vergely C. Nitric oxide synthase inhibition and oxidative stress in cardiovascular diseases: Possible therapeutic targets? Pharmacol Ther 2013; 140:239-57. [DOI: 10.1016/j.pharmthera.2013.07.004] [Citation(s) in RCA: 269] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 06/14/2013] [Indexed: 12/14/2022]
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21
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Walia A, Kang S, Silverman RB. Microwave-assisted protection of primary amines as 2,5-dimethylpyrroles and their orthogonal deprotection. J Org Chem 2013; 78:10931-7. [PMID: 24073706 DOI: 10.1021/jo401778e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Primary amines can be readily doubly protected as N-substituted 2,5-dimethylpyrroles. Although this protecting group is stable toward strong bases and nucleophiles, long reaction times are required for both the protection and deprotection steps, generally resulting in low deprotection yields. By employing microwave irradiation, protection and deprotection reaction times are dramatically reduced. Furthermore, deprotection with dilute hydrochloric acid in ethanol increases reaction yields. Diverse deprotection conditions have been developed in conjunction with microwave irradiation, so that protection as an N-substituted 2,5-dimethylpyrrole can be orthogonal to other standard amine protecting groups, such as tert-butyloxycarbonyl (Boc), carbobenzyloxy (Cbz), and 9-fluorenylmethyloxycarbonyl (Fmoc).
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Affiliation(s)
- Amit Walia
- Department of Chemistry, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University , Evanston, Illinois 60208, United States
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22
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Jing Q, Li H, Chreifi G, Roman LJ, Martásek P, Poulos TL, Silverman RB. Chiral linkers to improve selectivity of double-headed neuronal nitric oxide synthase inhibitors. Bioorg Med Chem Lett 2013; 23:5674-9. [PMID: 23993333 DOI: 10.1016/j.bmcl.2013.08.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 07/29/2013] [Accepted: 08/05/2013] [Indexed: 10/26/2022]
Abstract
To develop potent and selective nNOS inhibitors, new double-headed molecules with chiral linkers that derive from natural amino acids or their derivatives have been designed. The new structures contain two ether bonds, which greatly simplifies the synthesis and accelerates structure optimization. Inhibitor (R)-6b exhibits a potency of 32nM against nNOS and is 475 and 244 more selective for nNOS over eNOS and iNOS, respectively. Crystal structures show that the additional binding between the aminomethyl moiety of 6b and the two heme propionates in nNOS, but not eNOS, is the structural basis for its high selectivity. This work demonstrates the importance of stereochemistry in this class of molecules, which significantly influences the potency and selectivity of the inhibitors. The structure-activity information gathered here provides a guide for future structure optimization.
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Affiliation(s)
- Qing Jing
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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