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Characterization of Streptomyces piniterrae sp. nov. and Identification of the Putative Gene Cluster Encoding the Biosynthesis of Heliquinomycins. Microorganisms 2020; 8:microorganisms8040495. [PMID: 32244447 PMCID: PMC7232196 DOI: 10.3390/microorganisms8040495] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 03/28/2020] [Accepted: 03/30/2020] [Indexed: 01/29/2023] Open
Abstract
A novel actinomycete producing heliquinomycin and 9’-methoxy-heliquinomycin, designated strain jys28T, was isolated from rhizosphere soil of Pinus yunnanensis and characterized using a polyphasic approach. The strain had morphological characteristics and chemotaxonomic properties identical to those of members of the genus Streptomyces. It formed spiral chains of spores with spiny surfaces. The menaquinones detected were MK-9(H6), MK-9(H8) and MK-9(H4). The major fatty acids were iso-C16:0, C15:0, C16:1ω7с and anteiso-C15:0. The phospholipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine and phosphatidylinositol mannoside. The DNA G + C content of the draft genome sequence, consisting of 8.5 Mbp, was 70.6%. Analysis of the 16S rRNA gene sequence showed that strain jys28T belongs to the genus Streptomyces with the highest sequence similarities to Streptomyces chattanoogensis NBRC 13058T (99.2%) and Streptomyces lydicus DSM 40002T (99.2%) and phylogenetically clustered with them. Multilocus sequence analysis based on five other house-keeping genes (atpD, gyrB, rpoB, recA and trpB) and the low level of DNA–DNA relatedness and phenotypic differences allowed the novel isolate to be differentiated from its most closely related strains. Therefore, the strain is concluded to represent a novel species of the genus Streptomyces, for which the name Streptomycespiniterrae sp. nov. is proposed. Furthermore, the putative biosynthetic gene cluster of heliquinomycins was identified and the biosynthetic pathway was discussed. The type strain is jys28T (=CCTCC AA 2018051T =DSM 109823T).
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2
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Applications of metal and non-metal catalysts for the synthesis of oxygen containing five-membered polyheterocylces: a mini review. SN APPLIED SCIENCES 2019. [DOI: 10.1007/s42452-019-1007-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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3
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Kaur N, Bhardwaj P, Devi M, Verma Y, Grewal P. Gold-catalyzed C–O bond forming reactions for the synthesis of six-membered O-heterocycles. SN APPLIED SCIENCES 2019. [DOI: 10.1007/s42452-019-0920-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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4
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Yi L, Lü X. New Strategy on Antimicrobial-resistance: Inhibitors of DNA Replication Enzymes. Curr Med Chem 2019; 26:1761-1787. [PMID: 29110590 DOI: 10.2174/0929867324666171106160326] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/31/2017] [Accepted: 10/30/2017] [Indexed: 12/12/2022]
Abstract
BACKGROUND Antimicrobial resistance is found in all microorganisms and has become one of the biggest threats to global health. New antimicrobials with different action mechanisms are effective weapons to fight against antibiotic-resistance. OBJECTIVE This review aims to find potential drugs which can be further developed into clinic practice and provide clues for developing more effective antimicrobials. METHODS DNA replication universally exists in all living organisms and is a complicated process in which multiple enzymes are involved in. Enzymes in bacterial DNA replication of initiation and elongation phases bring abundant targets for antimicrobial development as they are conserved and indispensable. In this review, enzyme inhibitors of DNA helicase, DNA primase, topoisomerases, DNA polymerase and DNA ligase were discussed. Special attentions were paid to structures, activities and action modes of these enzyme inhibitors. RESULTS Among these enzymes, type II topoisomerase is the most validated target with abundant inhibitors. For type II topoisomerase inhibitors (excluding quinolones), NBTIs and benzimidazole urea derivatives are the most promising inhibitors because of their good antimicrobial activity and physicochemical properties. Simultaneously, DNA gyrase targeted drugs are particularly attractive in the treatment of tuberculosis as DNA gyrase is the sole type II topoisomerase in Mycobacterium tuberculosis. Relatively, exploitation of antimicrobial inhibitors of the other DNA replication enzymes are primeval, in which inhibitors of topo III are even blank so far. CONCLUSION This review demonstrates that inhibitors of DNA replication enzymes are abundant, diverse and promising, many of which can be developed into antimicrobials to deal with antibioticresistance.
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Affiliation(s)
- Lanhua Yi
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi Province 712100, China
| | - Xin Lü
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi Province 712100, China
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5
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Kemung HM, Tan LTH, Khan TM, Chan KG, Pusparajah P, Goh BH, Lee LH. Streptomyces as a Prominent Resource of Future Anti-MRSA Drugs. Front Microbiol 2018; 9:2221. [PMID: 30319563 PMCID: PMC6165876 DOI: 10.3389/fmicb.2018.02221] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/30/2018] [Indexed: 01/21/2023] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) pose a significant health threat as they tend to cause severe infections in vulnerable populations and are difficult to treat due to a limited range of effective antibiotics and also their ability to form biofilm. These organisms were once limited to hospital acquired infections but are now widely present in the community and even in animals. Furthermore, these organisms are constantly evolving to develop resistance to more antibiotics. This results in a need for new clinically useful antibiotics and one potential source are the Streptomyces which have already been the source of several anti-MRSA drugs including vancomycin. There remain large numbers of Streptomyces potentially undiscovered in underexplored regions such as mangrove, deserts, marine, and freshwater environments as well as endophytes. Organisms from these regions also face significant challenges to survival which often result in the production of novel bioactive compounds, several of which have already shown promise in drug development. We review the various mechanisms of antibiotic resistance in MRSA and all the known compounds isolated from Streptomyces with anti-MRSA activity with a focus on those from underexplored regions. The isolation of the full array of compounds Streptomyces are potentially capable of producing in the laboratory has proven a challenge, we also review techniques that have been used to overcome this obstacle including genetic cluster analysis. Additionally, we review the in vivo work done thus far with promising compounds of Streptomyces origin as well as the animal models that could be used for this work.
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Affiliation(s)
- Hefa Mangzira Kemung
- Novel Bacteria and Drug Discovery Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Biofunctional Molecule Exploratory Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia
| | - Loh Teng-Hern Tan
- Novel Bacteria and Drug Discovery Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Biofunctional Molecule Exploratory Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
| | - Tahir Mehmood Khan
- Novel Bacteria and Drug Discovery Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Biofunctional Molecule Exploratory Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,The Institute of Pharmaceutical Sciences (IPS), University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.,International Genome Centre, Jiangsu University, Zhenjiang, China
| | - Priyia Pusparajah
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
| | - Bey-Hing Goh
- Novel Bacteria and Drug Discovery Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Biofunctional Molecule Exploratory Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Center of Health Outcomes Research and Therapeutic Safety (Cohorts), School of Pharmaceutical Sciences, University of Phayao, Mueang Phayao, Thailand
| | - Learn-Han Lee
- Novel Bacteria and Drug Discovery Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Biofunctional Molecule Exploratory Research Group, Biomedicine Research Advancement Centre, School of Pharmacy, Monash University Malaysia, Bandar Sunway, Malaysia.,Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia.,Center of Health Outcomes Research and Therapeutic Safety (Cohorts), School of Pharmaceutical Sciences, University of Phayao, Mueang Phayao, Thailand
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6
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Seo YS, Kang YH. The Human Replicative Helicase, the CMG Complex, as a Target for Anti-cancer Therapy. Front Mol Biosci 2018; 5:26. [PMID: 29651420 PMCID: PMC5885281 DOI: 10.3389/fmolb.2018.00026] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 03/12/2018] [Indexed: 12/14/2022] Open
Abstract
DNA helicases unwind or rearrange duplex DNA during replication, recombination and repair. Helicases of many pathogenic organisms such as viruses, bacteria, and protozoa have been studied as potential therapeutic targets to treat infectious diseases, and human DNA helicases as potential targets for anti-cancer therapy. DNA replication machineries perform essential tasks duplicating genome in every cell cycle, and one of the important functions of these machineries are played by DNA helicases. Replicative helicases are usually multi-subunit protein complexes, and the minimal complex active as eukaryotic replicative helicase is composed of 11 subunits, requiring a functional assembly of two subcomplexes and one protein. The hetero-hexameric MCM2-7 helicase is activated by forming a complex with Cdc45 and the hetero-tetrameric GINS complex; the Cdc45-Mcm2-7-GINS (CMG) complex. The CMG complex can be a potential target for a treatment of cancer and the feasibility of this replicative helicase as a therapeutic target has been tested recently. Several different strategies have been implemented and are under active investigations to interfere with helicase activity of the CMG complex. This review focuses on the molecular function of the CMG helicase during DNA replication and its relevance to cancers based on data published in the literature. In addition, current efforts made to identify small molecules inhibiting the CMG helicase to develop anti-cancer therapeutic strategies were summarized, with new perspectives to advance the discovery of the CMG-targeting drugs.
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Affiliation(s)
- Yeon-Soo Seo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Young-Hoon Kang
- Core Protein Resources Center, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
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7
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Wilsdorf M, Sörgel S, Reissig HU. Lessons Learned During Spiroketalization Experiments: Progress and Setbacks in the Preparation of Oxygenated Rubromycins and Synthesis of 3′-Deoxyheliquinomycinone. European J Org Chem 2016. [DOI: 10.1002/ejoc.201601225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Michael Wilsdorf
- Institut für Chemie und Biochemie; Freie Universität Berlin; Takustr. 3 14195 Berlin Germany
| | - Sebastian Sörgel
- Institut für Chemie und Biochemie; Freie Universität Berlin; Takustr. 3 14195 Berlin Germany
| | - Hans-Ulrich Reissig
- Institut für Chemie und Biochemie; Freie Universität Berlin; Takustr. 3 14195 Berlin Germany
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8
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Wilsdorf M, Reissig HU. Towards γ-Rubromycin: Model Studies, Development of a C3Building Block, and Synthesis of 4′-Silyl-γ-rubromycin. European J Org Chem 2016. [DOI: 10.1002/ejoc.201601224] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michael Wilsdorf
- Institut für Chemie und Biochemie; Freie Universität Berlin; Takustr. 3 14195 Berlin Germany
| | - Hans-Ulrich Reissig
- Institut für Chemie und Biochemie; Freie Universität Berlin; Takustr. 3 14195 Berlin Germany
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9
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Elshahawi SI, Shaaban KA, Kharel MK, Thorson JS. A comprehensive review of glycosylated bacterial natural products. Chem Soc Rev 2015; 44:7591-697. [PMID: 25735878 PMCID: PMC4560691 DOI: 10.1039/c4cs00426d] [Citation(s) in RCA: 299] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A systematic analysis of all naturally-occurring glycosylated bacterial secondary metabolites reported in the scientific literature up through early 2013 is presented. This comprehensive analysis of 15 940 bacterial natural products revealed 3426 glycosides containing 344 distinct appended carbohydrates and highlights a range of unique opportunities for future biosynthetic study and glycodiversification efforts.
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Affiliation(s)
- Sherif I Elshahawi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA. and Center for Pharmaceutical Research and Innovation, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - Khaled A Shaaban
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA. and Center for Pharmaceutical Research and Innovation, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - Madan K Kharel
- School of Pharmacy, University of Maryland Eastern Shore, Princess Anne, Maryland, USA
| | - Jon S Thorson
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA. and Center for Pharmaceutical Research and Innovation, College of Pharmacy, University of Kentucky, Lexington, KY, USA
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10
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Atkinson DJ, Brimble MA. Isolation, biological activity, biosynthesis and synthetic studies towards the rubromycin family of natural products. Nat Prod Rep 2015; 32:811-40. [DOI: 10.1039/c4np00153b] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rubromycins are a unique family of natural products. This review covers their isolation, biological activity, biosynthesis and a detailed discussion of the diverse chemistry employed for total synthesis.
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Affiliation(s)
- Darcy J. Atkinson
- School of Chemical Sciences, The University of Auckland
- Auckland
- New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland
- Auckland
| | - Margaret A. Brimble
- School of Chemical Sciences, The University of Auckland
- Auckland
- New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland
- Auckland
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11
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The Mcm2-7 replicative helicase: a promising chemotherapeutic target. BIOMED RESEARCH INTERNATIONAL 2014; 2014:549719. [PMID: 25243149 PMCID: PMC4163376 DOI: 10.1155/2014/549719] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/08/2014] [Accepted: 08/10/2014] [Indexed: 02/05/2023]
Abstract
Numerous eukaryotic replication factors have served as chemotherapeutic targets. One replication factor that has largely escaped drug development is the Mcm2-7 replicative helicase. This heterohexameric complex forms the licensing system that assembles the replication machinery at origins during initiation, as well as the catalytic core of the CMG (Cdc45-Mcm2-7-GINS) helicase that unwinds DNA during elongation. Emerging evidence suggests that Mcm2-7 is also part of the replication checkpoint, a quality control system that monitors and responds to DNA damage. As the only replication factor required for both licensing and DNA unwinding, Mcm2-7 is a major cellular regulatory target with likely cancer relevance. Mutations in at least one of the six MCM genes are particularly prevalent in squamous cell carcinomas of the lung, head and neck, and prostrate, and MCM mutations have been shown to cause cancer in mouse models. Moreover various cellular regulatory proteins, including the Rb tumor suppressor family members, bind Mcm2-7 and inhibit its activity. As a preliminary step toward drug development, several small molecule inhibitors that target Mcm2-7 have been recently discovered. Both its structural complexity and essential role at the interface between DNA replication and its regulation make Mcm2-7 a potential chemotherapeutic target.
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12
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Harunari E, Imada C, Igarashi Y, Fukuda T, Terahara T, Kobayashi T. Hyaluromycin, a new hyaluronidase inhibitor of polyketide origin from marine Streptomyces sp. Mar Drugs 2014; 12:491-507. [PMID: 24451191 PMCID: PMC3917283 DOI: 10.3390/md12010491] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 12/28/2013] [Accepted: 12/31/2013] [Indexed: 11/24/2022] Open
Abstract
Hyaluromycin (1), a new member of the rubromycin family of antibiotics, was isolated from the culture extract of a marine-derived Streptomyces sp. as a HAase inhibitor on the basis of HAase activity screening. The structure of 1 was elucidated through the interpretation of NMR data for the compound and its 3″-O-methyl derivative in combination with an incorporation experiment with [1,2-13C2]acetate. The compound’s absolute configuration was determined by the comparison of its circular dichroism (CD) spectrum with those of other rubromycins. Hyaluromycin (1) consists of a γ-rubromycin core structure possessing a 2-amino-3-hydroxycyclopent-2-enone (C5N) unit as an amide substituent of the carboxyl function; both structural units have been reported only from actinomycetes. Hyaluromycin (1) displayed approximately 25-fold more potent hyaluronidase inhibitory activity against hyaluronidase than did glycyrrhizin, a known inhibitor of plant origin.
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Affiliation(s)
- Enjuro Harunari
- Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
| | - Chiaki Imada
- Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
| | - Yasuhiro Igarashi
- Biotechnology Research Center, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan.
| | - Takao Fukuda
- Biotechnology Research Center, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan.
| | - Takeshi Terahara
- Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
| | - Takeshi Kobayashi
- Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
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Sugiyama T, Chino M, Tsurimoto T, Nozaki N, Ishimi Y. Interaction of heliquinomycin with single-stranded DNA inhibits MCM4/6/7 helicase. ACTA ACUST UNITED AC 2011; 151:129-37. [DOI: 10.1093/jb/mvr130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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14
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Alcaide B, Almendros P, Alonso JM. Gold-catalyzed cyclizations of alkynol-based compounds: synthesis of natural products and derivatives. Molecules 2011; 16:7815-43. [PMID: 22143545 PMCID: PMC6264458 DOI: 10.3390/molecules16097815] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 09/05/2011] [Accepted: 09/08/2011] [Indexed: 11/18/2022] Open
Abstract
The last decade has witnessed dramatic growth in the number of reactions catalyzed by gold complexes because of their powerful soft Lewis acid nature. In particular, the gold-catalyzed activation of propargylic compounds has progressively emerged in recent years. Some of these gold-catalyzed reactions in alkynes have been optimized and show significant utility in organic synthesis. Thus, apart from significant methodology work, in the meantime gold-catalyzed cyclizations in alkynol derivatives have become an efficient tool in total synthesis. However, there is a lack of specific review articles covering the joined importance of both gold salts and alkynol-based compounds for the synthesis of natural products and derivatives. The aim of this Review is to survey the chemistry of alkynol derivatives under gold-catalyzed cyclization conditions and its utility in total synthesis, concentrating on the advances that have been made in the last decade, and in particular in the last quinquennium.
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Affiliation(s)
- Benito Alcaide
- Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica I, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040-Madrid, Spain
| | - Pedro Almendros
- Instituto de Química Orgánica General, CSIC, Juan de la Cierva 3, 28006-Madrid, Spain
| | - José M. Alonso
- Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica I, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040-Madrid, Spain
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Sperry J, Wilson ZE, Rathwell DCK, Brimble MA. Isolation, biological activity and synthesis of benzannulated spiroketal natural products. Nat Prod Rep 2010; 27:1117-37. [DOI: 10.1039/b911514p] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Rathwell D, Yang SH, Tsang K, Brimble M. An Efficient Formal Synthesis of the Human Telomerase Inhibitor (±)-γ-Rubromycin. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200903316] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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17
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Rathwell D, Yang SH, Tsang K, Brimble M. An Efficient Formal Synthesis of the Human Telomerase Inhibitor (±)-γ-Rubromycin. Angew Chem Int Ed Engl 2009; 48:7996-8000. [DOI: 10.1002/anie.200903316] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Choi PJ, Rathwell DC, Brimble MA. Synthesis of 6,6-bisbenzannulated spiroketals related to the rubromycins using a double intramolecular hetero-Michael addition (DIHMA). Tetrahedron Lett 2009. [DOI: 10.1016/j.tetlet.2009.02.030] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Ishimi Y, Sugiyama T, Nakaya R, Kanamori M, Kohno T, Enomoto T, Chino M. Effect of heliquinomycin on the activity of human minichromosome maintenance 4/6/7 helicase. FEBS J 2009; 276:3382-91. [PMID: 19438708 DOI: 10.1111/j.1742-4658.2009.07064.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The antibiotic heliquinomycin, which inhibits cellular DNA replication at a half-maximal inhibitory concentration (IC(50)) of 1.4-4 microM, was found to inhibit the DNA helicase activity of the human minichromosome maintenance (MCM) 4/6/7 complex at an IC(50) value of 2.4 microM. In contrast, 14 microM heliquinomycin did not inhibit significantly either the DNA helicase activity of the SV40 T antigen and Werner protein or the oligonucleotide displacement activity of human replication protein A. At IC(50) values of 25 and 6.5 microM, heliquinomycin inhibited the RNA priming and DNA polymerization activities, respectively, of human DNA polymerase-alpha/primase. Thus, of the enzymes studied, the MCM4/6/7 complex was the most sensitive to heliquinomycin; this suggests that MCM helicase is one of the main targets of heliquinomycin in vivo. It was observed that heliquinomycin did not inhibit the ATPase activity of the MCM4/6/7 complex to a great extent in the absence of single-stranded DNA. In contrast, heliquinomycin at an IC(50) value of 5.2 microM inhibited the ATPase activity of the MCM4/6/7 complex in the presence of single-stranded DNA. This suggests that heliquinomycin interferes with the interaction of the MCM4/6/7 complex with single-stranded DNA.
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Brasholz M, Reissig HU, Zimmer R. Sugars, alkaloids, and heteroaromatics: exploring heterocyclic chemistry with alkoxyallenes. Acc Chem Res 2009; 42:45-56. [PMID: 18921986 DOI: 10.1021/ar800011h] [Citation(s) in RCA: 296] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As master craftsmen, modern synthetic chemists are challenged to achieve remarkable feats of efficiency and elegance toward molecular targets. The nature of this pursuit necessitates the collection of synthetic repertoires that are tried and true. With methodologies and pathways increasingly scrutinized, the adept chemist must seek out propitious tools to incorporate into the arsenal. With this in mind, this Account highlights the versatility of alkoxyallenes as precursors to valuable heterocyclic building blocks for such efforts as natural product synthesis. Accessed by the etherification of either propargyl alcohols or propargylic halides, alkoxyallenes are obtained after base-catalyzed isomerizations of the propargylic ethers. A host of umpolung synthons are available through this scheme after metalation, generating C(3) nucleophiles synthetically equivalent to vital anionic and zwitterionic synthons. Reactions with a diverse set of heteroatomic electrophiles yield carbohydrates, spiroketals, alkaloids, and heteroaromatics via [3 + 2] or [3 + 3] cyclizations. By employing lithiated alkoxyallenes into transformation routes, the natural product chemist can utilize this methodology as a viable resource in stereoselective synthesis. A survey of our own utilization of alkoxyallenes along synthetic pathways toward natural product targets reveals their suitability for generating advantageous precursors. A set of four stereoisomeric 2,6-dideoxyhexoses were stereoselectively obtained after an initial lithiated alkoxyallene and lactaldehyde cyclization, followed by the oxidative ring opening of the dihydrofurans. Through the addition of a lithiated alkoxyallene to a functionalized benzaldehyde, an essential spiroketal diastereomer was rapidly achieved in a few steps. We greatly benefitted from alkoxyallenes in the construction of complex nitrogen-containing synthetic targets, whether pyrrolidine alkaloids, substituted imidazole derivatives, or functionalized pyridines. A pinnacle example of their utility came from the coupling of alkoxyallenes to nitrones affording 1,2-oxazines, which served as a gateway to an array of novel polyfunctionalized compounds such as aminopolyols, hydroxylated pyrrolidines, or carbohydrate mimetics. Alkoxyallenes have proven themselves to be powerful C(3) building blocks toward complex molecular targets, revealing novel pathways to a variety of desirable highly functionalized heterocycles. In our view, the full extent of their synthetic utility has yet to be truly realized.
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Affiliation(s)
- Malte Brasholz
- Freie Universität Berlin, Institut für Chemie and Biochemie, Takustrasse 3, D-14195 Berlin, Germany
| | - Hans-Ulrich Reissig
- Freie Universität Berlin, Institut für Chemie and Biochemie, Takustrasse 3, D-14195 Berlin, Germany
| | - Reinhold Zimmer
- Freie Universität Berlin, Institut für Chemie and Biochemie, Takustrasse 3, D-14195 Berlin, Germany
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22
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Zhou G, Zhu J, Xie Z, Li Y. An Efficient Synthesis of Highly Functionalized [5,6] Aromatic Spiroketals by Hetero-Diels−Alder Reaction. Org Lett 2008; 10:721-4. [PMID: 18266379 DOI: 10.1021/ol7029068] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guanglian Zhou
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China
| | - Jianrong Zhu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China
| | - Zhixiang Xie
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China
| | - Ying Li
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China
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23
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Lowell AN, Fennie MW, Kozlowski MC. A Concise Synthesis of the Naphthalene Portion of Purpuromycin. J Org Chem 2008; 73:1911-8. [DOI: 10.1021/jo7024114] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew N. Lowell
- Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Michael W. Fennie
- Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
| | - Marisa C. Kozlowski
- Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
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24
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Shankar J, Tuteja R. UvrD helicase of Plasmodium falciparum. Gene 2007; 410:223-33. [PMID: 18242886 DOI: 10.1016/j.gene.2007.12.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 12/04/2007] [Accepted: 12/13/2007] [Indexed: 11/25/2022]
Abstract
Malaria caused by the mosquito-transmitted parasite Plasmodium is the cause of enormous number of deaths every year in the tropical and subtropical areas of the world. Among four species of Plasmodium, Plasmodium falciparum causes most fatal form of malaria. With time, the parasite has developed insecticide and drug resistance. Newer strategies and advent of novel drug targets are required so as to combat the deadly form of malaria. Helicases is one such class of enzymes which has previously been suggested as potential antiviral and anticancer targets. These enzymes play an essential role in nearly all the nucleic acid metabolic processes, catalyzing the transient opening of the duplex nucleic acids in an NTP-dependent manner. DNA helicases from the PcrA/UvrD/Rep subfamily are important for the survival of the various organisms. Members from this subfamily can be targeted and inhibited by a variety of synthetic compounds. UvrD from this subfamily is the only member present in the P. falciparum genome, which shows no homology with UvrD from human and thus can be considered as a strong potential drug target. In this manuscript we provide an overview of UvrD family of helicases and bioinformatics analysis of UvrD from P. falciparum.
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Affiliation(s)
- Jay Shankar
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
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25
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Akai S, Kakiguchi K, Nakamura Y, Kuriwaki I, Dohi T, Harada S, Kubo O, Morita N, Kita Y. Total synthesis of (+/-)-gamma-rubromycin on the basis of two aromatic Pummerer-type reactions. Angew Chem Int Ed Engl 2007; 46:7458-61. [PMID: 17702074 DOI: 10.1002/anie.200702382] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Shuji Akai
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6, Yamada-oka, Suita, Osaka 565-0871, Japan
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26
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Akai S, Kakiguchi K, Nakamura Y, Kuriwaki I, Dohi T, Harada S, Kubo O, Morita N, Kita Y. Total Synthesis of (±)-γ-Rubromycin on the Basis of Two Aromatic Pummerer-Type Reactions. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200702382] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Brasholz M, Sörgel S, Azap C, Reißig H. Rubromycins: Structurally Intriguing, Biologically Valuable, Synthetically Challenging Antitumour Antibiotics. European J Org Chem 2007. [DOI: 10.1002/ejoc.200601054] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Malte Brasholz
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany, Fax: +49‐30‐838‐55367
| | - Sebastian Sörgel
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany, Fax: +49‐30‐838‐55367
| | - Cengiz Azap
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany, Fax: +49‐30‐838‐55367
| | - Hans‐Ulrich Reißig
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany, Fax: +49‐30‐838‐55367
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28
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Synthesis of aromatic spiroacetals related to γ-rubromycin based on a 3H-spiro[1-benzofuran-2,2′-chromane] skeleton. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.02.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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29
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Brasholz M, Reißig HU. Oxidative Spaltung von 3-Alkoxy-2,5-dihydrofuranen und ihre Anwendung in der De-novo-Synthese seltener Monosaccharide am Beispiel vonL-Cymarose. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604078] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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30
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Brasholz M, Reissig HU. Oxidative Cleavage of 3-Alkoxy-2,5-dihydrofurans and its Application to the De Novo Synthesis of Rare Monosaccharides as Exemplified byL-Cymarose. Angew Chem Int Ed Engl 2007; 46:1634-7. [PMID: 17219450 DOI: 10.1002/anie.200604078] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Malte Brasholz
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
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31
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Sörgel S, Azap C, Reißig HU. Preparation of Highly Alkoxy-Substituted Naphthaldehyde Derivatives – A Regioselective Approach to Building Blocks for the Synthesis of Rubromycins. European J Org Chem 2006. [DOI: 10.1002/ejoc.200600353] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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32
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Sörgel S, Azap C, Reissig HU. Synthesis of Bisbenzannulated SpiroketalsModel Studies for a Modular Approach to Rubromycins. Org Lett 2006; 8:4875-8. [PMID: 17020325 DOI: 10.1021/ol061932w] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] A highly flexible synthesis of bisbenzannulated spiroketals is described with additions of lithiated methoxyallene to aryl aldehydes and Heck reactions as key steps. Subsequent hydrogenations and ketalizations afforded the desired spiroketals in good yields and with predominating trans-configuration. With model compound 30, already bearing the fully substituted naphthyl core of rubromycins, the ketalization proceeded efficiently providing the expected product 31 and the isopropoxy compound 32. Both products are advanced model compounds of heliquinomycin.
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Affiliation(s)
- Sebastian Sörgel
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany
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33
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Abaev VT, Dmitriev AS, Podelyakin SA, Butin AV, Gutnov AV. Furan ring opening - isocoumarine ring closure: A recyclization reaction of 2-carboxyaryldifurylmethanes. J Heterocycl Chem 2006. [DOI: 10.1002/jhet.5570430510] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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34
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Convergent route to the purpuromycin bisphenolic spiroketal: hydrogen bonding control of spiroketalization stereochemistry. Tetrahedron Lett 2006. [DOI: 10.1016/j.tetlet.2006.05.044] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Waters SP, Fennie MW, Kozlowski MC. Investigation of a Convergent Route to Purpuromycin: Benzofuran Formation vs Spiroketalization. Org Lett 2006; 8:3243-6. [PMID: 16836376 DOI: 10.1021/ol061112j] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[Structure: see text] A mild and efficient [3+2] nitrile oxide/olefin cycloaddition allows coupling of the highly functionalized naphthalene and isocoumarin hemispheres of purpuromycin. A rationale of the inability of advanced keto alcohols to spirocyclize is presented based upon a systematic examination of the electronic factors present in these systems and suggests that the biosynthesis of purpuromycin does not proceed through open-chain intermediates.
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Affiliation(s)
- Stephen P Waters
- Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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36
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A facile synthesis of fused aromatic spiroacetals based on the 3,4,3′,4′-tetrahydro-2,2′-spirobis(2H-1-benzopyran) skeleton. Tetrahedron 2006. [DOI: 10.1016/j.tet.2006.04.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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37
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Zhou G, Zheng D, Da S, Xie Z, Li Y. Expeditious synthesis of the aromatic spiroketal skeleton using hetero-Diels–Alder cycloaddition. Tetrahedron Lett 2006. [DOI: 10.1016/j.tetlet.2006.03.092] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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38
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Tsang KY, Brimble MA, Bremner JB. Use of a Sonogashira−Acetylide Coupling Strategy for the Synthesis of the Aromatic Spiroketal Skeleton of γ-Rubromycin. Org Lett 2003; 5:4425-7. [PMID: 14602016 DOI: 10.1021/ol035723c] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] The synthesis of the fused aromatic spiroketal core of gamma-rubromycin is described via addition of an aryl acetylide fragment to an aryl acetaldehyde fragment. In turn, the aryl acetylene precursor was readily prepared with use of a Sonogashira reaction.
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Affiliation(s)
- Kit Y Tsang
- Department of Chemistry, University of Auckland, 23 Symonds Street, Auckland, New Zealand
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39
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Van De Water RW, Pettus TR. o-Quinone methides: intermediates underdeveloped and underutilized in organic synthesis. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00496-9] [Citation(s) in RCA: 420] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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40
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Qin D, Ren RX, Siu T, Zheng C, Danishefsky SJ. Studies in the Total Synthesis of Heliquinomycinone: Proof of Concept and Assembly of a Fully Mature Spirocyclization Precursor. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20011217)113:24<4845::aid-ange4845>3.0.co;2-b] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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41
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Qin D, Ren RX, Siu T, Zheng C, Danishefsky SJ. Studies in the Total Synthesis of Heliquinomycinone: Proof of Concept and Assembly of a Fully Mature Spirocyclization Precursor This work was supported by the National Institutes of Health (Grant numbers: AI 16943 and HL25848). A Postdoctoral Fellowship is gratefully acknowledged by R.X.R. (NIH, Grant Number IF32EY06750-0181). The authors thank Dr. Daniel Chen for important initial experiments, Dr. Brian Bridgewater and Prof. Ged Parkin of Columbia University for X-ray crystal structure analysis of 11 a, and Yashuiro Itagaki for high-resolution mass spectral analyses. Angew Chem Int Ed Engl 2001; 40:4709-4713. [PMID: 12404391 DOI: 10.1002/1521-3773(20011217)40:24<4709::aid-anie4709>3.0.co;2-q] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Donghui Qin
- Department of Chemistry, Columbia University Havemeyer Hall, New York, NY, 10021 (USA)
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42
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Xu H, Ziegelin G, Schröder W, Frank J, Ayora S, Alonso JC, Lanka E, Saenger W. Flavones inhibit the hexameric replicative helicase RepA. Nucleic Acids Res 2001; 29:5058-66. [PMID: 11812837 PMCID: PMC97556 DOI: 10.1093/nar/29.24.5058] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2001] [Revised: 10/08/2001] [Accepted: 10/08/2001] [Indexed: 11/14/2022] Open
Abstract
Helicases couple the hydrolysis of nucleoside triphosphates (NTPs) to the unwinding of double-stranded nucleic acids and are essential in DNA metabolism. Thus far, no inhibitors are known for helicases except heliquinomycin isolated from Streptomyces sp. As the three-dimensional structure of the hexameric replicative DNA helicase RepA encoded by the broad host-range plasmid RSF1010 is known, this protein served as a model helicase to search for inhibitory compounds. The commercially available flavone derivatives luteolin, morin, myricetin and dimyricetin (an oxidation product of myricetin) inhibited the ATPase and double-stranded DNA unwinding activities of RepA. Dimyricetin was the most effective inhibitor for both activities. Single-stranded DNA-dependent RepA ATPase activity is inhibited non-competitively by all four compounds. This finding contrasts the inhibition of phosphoinositide 3-kinase by flavones that fit into the ATP binding pocket of this enzyme. Myricetin also inhibited the growth of a Gram-positive and a Gram-negative bacterial species. As we found other hexameric and non-hexameric prokaryotic helicases to be differentially sensitive to myricetin, flavones may provide substructures for the design of molecules helpful for unraveling the mechanism of helicase action and of novel pharmacologically useful molecules.
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Affiliation(s)
- H Xu
- Institut für Kristallographie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany
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43
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Abstract
[reaction: see text]. A synthesis of a reduced version of the naphthazarin found in the rubromycin class of natural products is reported. The naphthalene ring system is formed via a Dötz reaction with a symmetrical alkyne. Differentiation between the C1' and C3' groups of the Dötz adduct is achieved by selective oxidation since the two methylene groups possess different oxidation potentials.
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Affiliation(s)
- X Xie
- Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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44
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45
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46
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Thrash TP, Welton TD, Behar V. Synthesis of an elaborated heliquinomycin isocoumarin moiety. Tetrahedron Lett 2000. [DOI: 10.1016/s0040-4039(99)01966-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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47
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Capecchi T, de Koning CB, Michael JP. Nitroalkenes as precursors to the aromatic spiroketal skeleton of γ-rubromycin. A Nef-type reaction mediated by Pearlman's catalyst. Tetrahedron Lett 1998. [DOI: 10.1016/s0040-4039(98)01046-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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