1
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Avalon N, Reis MA, Thornburg CC, Williamson RT, Petras D, Aron AT, Neuhaus GF, Al-Hindy M, Mitrevska J, Ferreira L, Morais J, El Abiead Y, Glukhov E, Alexander KL, Vulpanovici FA, Bertin MJ, Whitner S, Choi H, Spengler G, Blinov K, Almohammadi AM, Shaala LA, Kew WR, Paša-Tolić L, Youssef DTA, Dorrestein PC, Vasconcelos V, Gerwick L, McPhail KL, Gerwick WH. Leptochelins A-C, Cytotoxic Metallophores Produced by Geographically Dispersed Leptothoe Strains of Marine Cyanobacteria. J Am Chem Soc 2024; 146:18626-18638. [PMID: 38918178 PMCID: PMC11240249 DOI: 10.1021/jacs.4c05399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 06/10/2024] [Accepted: 06/11/2024] [Indexed: 06/27/2024]
Abstract
Metals are important cofactors in the metabolic processes of cyanobacteria, including photosynthesis, cellular respiration, DNA replication, and the biosynthesis of primary and secondary metabolites. In adaptation to the marine environment, cyanobacteria use metallophores to acquire trace metals when necessary as well as to reduce potential toxicity from excessive metal concentrations. Leptochelins A-C were identified as structurally novel metallophores from three geographically dispersed cyanobacteria of the genus Leptothoe. Determination of the complex structures of these metabolites presented numerous challenges, but they were ultimately solved using integrated data from NMR, mass spectrometry and deductions from the biosynthetic gene cluster. The leptochelins are comprised of halogenated linear NRPS-PKS hybrid products with multiple heterocycles that have potential for hexadentate and tetradentate coordination with metal ions. The genomes of the three leptochelin producers were sequenced, and retrobiosynthetic analysis revealed one candidate biosynthetic gene cluster (BGC) consistent with the structure of leptochelin. The putative BGC is highly homologous in all three Leptothoe strains, and all possess genetic signatures associated with metallophores. Postcolumn infusion of metals using an LC-MS metabolomics workflow performed with leptochelins A and B revealed promiscuous binding of iron, copper, cobalt, and zinc, with greatest preference for copper. Iron depletion and copper toxicity experiments support the hypothesis that leptochelin metallophores may play key ecological roles in iron acquisition and in copper detoxification. In addition, the leptochelins possess significant cytotoxicity against several cancer cell lines.
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Affiliation(s)
- Nicole
E. Avalon
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Mariana A. Reis
- CIIMAR/CIMAR,
Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Matosinhos 4450-208, Portugal
| | | | - R. Thomas Williamson
- Department
of Chemistry and Biochemistry, University
of North Carolina Wilmington, Wilmington, North Carolina 28403, United States
| | - Daniel Petras
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, United States
- Department
of Biochemistry, University of California
Riverside, Riverside, California 92507, United States
- CMFI Cluster
of Excellence, University of Tuebingen, Tuebingen 72706, Germany
| | - Allegra T. Aron
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, United States
- Department
of Chemistry and Biochemistry, University
of Denver, Denver, Colorado 80210, United States
| | - George F. Neuhaus
- College
of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - Momen Al-Hindy
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Jana Mitrevska
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Leonor Ferreira
- CIIMAR/CIMAR,
Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Matosinhos 4450-208, Portugal
| | - João Morais
- CIIMAR/CIMAR,
Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Matosinhos 4450-208, Portugal
| | - Yasin El Abiead
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, United States
| | - Evgenia Glukhov
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Kelsey L. Alexander
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
- Department
of Chemistry and Biochemistry, University
of California San Diego, La Jolla, California 92093, United States
| | | | - Matthew J. Bertin
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Syrena Whitner
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Hyukjae Choi
- College
of Pharmacy, Yeungnam University, Gyeongsan, Gyeong-buk 38541, South Korea
| | - Gabriella Spengler
- Department
of Medical Microbiology, Albert Szent-Györgyi Health Center
and Albert Szent-Györgyi Medical School, University of Szeged, Szeged 6725, Hungary
| | - Kirill Blinov
- Molecule
Apps, LLC, Corvallis, Oregon 97330, United States
| | - Ameen M. Almohammadi
- Department
of Pharmacy Practice, Faculty of Pharmacy, King Abdulaziz University, Jeddah 21589, Kingdom
of Saudi Arabia
| | - Lamiaa A. Shaala
- Suez Canal
University Hospital, Suez Canal University, Ismailia 41522, Egypt
| | - William R. Kew
- Environmental
Molecular Sciences Laboratory, Pacific Northwest
National Laboratory, Richland, Washington 99354, United States
| | - Ljiljana Paša-Tolić
- Environmental
Molecular Sciences Laboratory, Pacific Northwest
National Laboratory, Richland, Washington 99354, United States
| | - Diaa T. A. Youssef
- Department
of Natural Products, Faculty of Pharmacy, King Abdulaziz University, Jeddah 21589, Kingdom
of Saudi Arabia
- Department
of Pharmacognosy, Faculty of Pharmacy, Suez
Canal University, Ismailia 41522, Egypt
| | - Pieter C. Dorrestein
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, United States
| | - Vitor Vasconcelos
- CIIMAR/CIMAR,
Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Matosinhos 4450-208, Portugal
| | - Lena Gerwick
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
| | - Kerry L. McPhail
- College
of Pharmacy, Oregon State University, Corvallis, Oregon 97331, United States
| | - William H. Gerwick
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, United States
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, United States
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2
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Wang H, Zhang S, Zhang J. The copper resistance mechanism in a newly isolated Pseudoxanthomonas spadix ZSY-33. ENVIRONMENTAL MICROBIOLOGY REPORTS 2023; 15:484-496. [PMID: 37328952 PMCID: PMC10667631 DOI: 10.1111/1758-2229.13163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 05/05/2023] [Indexed: 06/18/2023]
Abstract
Resolving the heavy metal resistance mechanisms of microbes is crucial for understanding the bioremediation of the ecological environment. In this study, a multiple heavy metal resistance bacterium, Pseudoxanthomonas spadix ZSY-33 was isolated and characterized. The copper resistance mechanism was revealed by analysis of the physiological traits, copper distribution, and genomic and transcriptomic data of strain ZSY-33 cultured with different concentrations of copper. The growth inhibition assay in basic medium showed that the growth of strain ZSY-33 was inhibited in the presence of 0.5 mM copper. The production of extracellular polymeric substances increased at a lower concentration of copper and decreased at a higher concentration of copper. Integrative analysis of genomic and transcriptomic, the copper resistance mechanism in strain ZSY-33 was elucidated. At a lower concentration of copper, the Cus and Cop systems were responsible for the homeostasis of intracellular copper. As the concentration of copper increased, multiple metabolism pathways, including the metabolism of sulfur, amino acids, and pro-energy were cooperated with the Cus and Cop systems to deal with copper stress. These results indicated a flexible copper resistance mechanism in strain ZSY-33, which may acquire from the long-term interaction with the living environment.
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Affiliation(s)
- Hongjie Wang
- Hebei Key Laboratory of Close‐to‐Nature Restoration Technology of WetlandsHebei UniversityBaodingPeople's Republic of China
- Institute of Xiong'an New AreaHebei UniversityBaodingPeople's Republic of China
- School of Eco‐EnvironmentHebei UniversityBaodingPeople's Republic of China
- College of Life ScienceHebei UniversityBaodingPeople's Republic of China
| | - Siyao Zhang
- Hebei Key Laboratory of Close‐to‐Nature Restoration Technology of WetlandsHebei UniversityBaodingPeople's Republic of China
- School of Eco‐EnvironmentHebei UniversityBaodingPeople's Republic of China
| | - Jing Zhang
- Hebei Key Laboratory of Close‐to‐Nature Restoration Technology of WetlandsHebei UniversityBaodingPeople's Republic of China
- Institute of Xiong'an New AreaHebei UniversityBaodingPeople's Republic of China
- School of Eco‐EnvironmentHebei UniversityBaodingPeople's Republic of China
- College of Life ScienceHebei UniversityBaodingPeople's Republic of China
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3
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Jiao X, Huang W, Wang A, Wu B, Kang Q, Luo X, Bai L, Deng Z. Crystallographic Deciphering of Spontaneous Self-Assembly of Achiral Calciphores to Chiral Complexes. Chemistry 2023; 29:e202203127. [PMID: 36408990 DOI: 10.1002/chem.202203127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 11/23/2022]
Abstract
Thiapyricins (TPC-A/B, 1 and 2), which are new metallophore scaffolds exhibiting selective divalent cation binding property, were produced in response to metal-deprived conditions by Saccharothrix sp. TRM_47004 isolated from the Lop Nor Salt Lake. TPCs represent a thiazolyl-pyridine skeleton of a calcium-binding natural product, calciphore, owing to the selectivity to calcium ions among diverse metal ions. The thiapyricins exhibited notable co-crystalline characteristics of the apo- and holo-forms with racemic enantiomers comprising a pair of space isomers in a Δ/Λ-form. Therefore, we postulated a mechanism for the four-hierarchical self-assembly of achiral natural products into chiral complexes. Furthermore, their metal-chelating trait aided the adaptation of the host during metal starvation by increasing the production of TPCs. This study presents a structural paradigm of a new calciphore, provides insight into the mechanism of natural product assembly, and highlights the causality between the production of the metallophore and metallic habitats.
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Affiliation(s)
- Xingzhi Jiao
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Wei Huang
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Anqi Wang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Banghao Wu
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Qianjin Kang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Xiaoxia Luo
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Linquan Bai
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China.,College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Zixin Deng
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
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4
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Yang T, Huang C, Jia J, Wu F, Ni F. A Facile Synthesis of 2-Oxazolines via Dehydrative Cyclization Promoted by Triflic Acid. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27249042. [PMID: 36558175 PMCID: PMC9781752 DOI: 10.3390/molecules27249042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 12/10/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022]
Abstract
2-oxazolines are common moieties in numerous natural products, pharmaceuticals, and functional copolymers. Current methods for synthesizing 2-oxazolines mainly rely on stoichiometric dehydration agents or catalytic dehydration promoted by specific catalysts. These conditions either generate stoichiometric amounts of waste or require forcing azeotropic reflux conditions. As such, a practical and robust method that promotes dehydrative cyclization while generating no byproducts would be attractive to oxazoline production. Herein, we report a triflic acid (TfOH)-promoted dehydrative cyclization of N-(2-hydroxyethyl)amides for synthesizing 2-oxazolines. This reaction tolerates various functional groups and generates water as the only byproduct. This method affords oxazoline with inversion of α-hydroxyl stereochemistry, suggesting that alcohol is activated as a leaving group under these conditions. Furthermore, the one-pot synthesis protocol of 2-oxazolines directly from carboxylic acids and amino alcohols is also provided.
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Affiliation(s)
- Tao Yang
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
- Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, China
| | - Chengjie Huang
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
- Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, China
| | - Jingyang Jia
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
- Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, China
| | - Fan Wu
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
- Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, China
- Correspondence: (F.W.); (F.N.)
| | - Feng Ni
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
- Qian Xuesen Collaborative Research Center of Astrochemistry and Space Life Sciences, Ningbo University, Ningbo 315211, China
- Correspondence: (F.W.); (F.N.)
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5
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Genome Sequence of
Halomonas
sp. Strain MS1, a Metallophore-Producing, Algal Growth-Promoting Marine Bacterium Isolated from the Green Seaweed Ulva mutabilis (Chlorophyta). Microbiol Resour Announc 2022; 11:e0068522. [DOI: 10.1128/mra.00685-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
We report the draft genome sequence of the marine gammaproteobacterium
Halomonas
sp. strain MS1, isolated from the green seaweed
Ulva mutabilis
(Chlorophyta), which releases metallophores fostering macroalga-bacterium interactions. The 4.6-Mbp sequence, which was obtained using PacBio technology, harbors 4,166 predicted coding sequences, including gene clusters for siderophore production.
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6
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Alarcon-Enos J, Quiroz-Carreño S, Muñoz-Nuñez E, Silva FL, Devotto-Moreno L, Seigler DS, Pastene-Navarrete E, Cespedes-Acuña CL. Cyclopeptide alkaloids from Discaria chacaye (Rhamnaceae) as result of symbiosis with Frankia (Actinomycetales). Chem Biodivers 2022; 19:e202200630. [PMID: 35916106 DOI: 10.1002/cbdv.202200630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 07/27/2022] [Indexed: 11/07/2022]
Abstract
Cyclopeptide alkaloids with different biological activities are present in plants of the family Rhamnaceae. Plants of this family grow in a symbiotic relationship with aerobic Gram-positive actinomycetes belonging to the genus Frankia . This goal of this research was a study of the comparative profile of alkaloids present in Discaria chacaye and to establish a connection between the presence or absence of Frankia sp. and the alkaloids. In addition, insecticidal activities of the alkaloidal extract were examined. A total of 24 alkaloids were identified, of which 12 have a benzylisoquinoline skeleton, 9 were cyclopeptides, 2 isoquinolines, and 1 an aporphine. The presence of cyclopeptide alkaloids is associated with Frankia nodules in the plant root. The alkaloid extracts showed insecticidal activity with mortality dose-dependence and LD 50 values between 44 to 71 µg/mL.
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Affiliation(s)
- Julio Alarcon-Enos
- Universidad del Bio Bio, Ciencias Basicas, Avenida Andrés Bello 720, 38000708, Chillan, CHILE
| | - Soledad Quiroz-Carreño
- Universidad del Bio-Bio - Sede Chillan, Ciencias Básicas, Avenida Andrés Bello 720, 38000708, Chillan, CHILE
| | - Evelyn Muñoz-Nuñez
- Universidad del Bio-Bio - Sede Chillan, Ciencias Básicas, Avenida Andrés Bello 720, 38000708, Chillan, CHILE
| | - Fabiana L Silva
- Universidade Paulista Campus de Bauru Instituto de Ciências de Saúde: Universidade Paulista Campus de Bauru Instituto de Ciencias de Saude, Instituto de Ciencias da Saude, Av. Brigadeiro Luís Antônio, 3751, Sao Paulo, BRAZIL
| | - Luis Devotto-Moreno
- INIA: Instituto de Investigaciones Agropecuarias, Control Biológico, Av Vicente Mendez s7n, Chillan, CHILE
| | - David S Seigler
- : University of Illinois Urbana-Champaign Department of Chemistry, Deparment of Plant Biology, 1909 South Oak Street, Urbana-Champaing, UNITED STATES
| | - Edgar Pastene-Navarrete
- Universidad del Bio-Bio - Sede Chillan, Ciencias Básicas, Av Andres Bello 720, Chillan, CHILE
| | - Carlos L Cespedes-Acuña
- Universidad del Bio-Bio - Sede Chillan, Ciencias Básicas, Av Andres Bello 720, Chillan, CHILE
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7
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Mohr JF, Gama S, Roy S, Bellenger JP, Plass W, Wichard T. Hydroxypyridinones in nitrogen-fixing bacterial cultures: A metal buffer for molybdenum and simulation of natural conditions. METALLOMICS : INTEGRATED BIOMETAL SCIENCE 2022; 14:6650223. [PMID: 35881466 DOI: 10.1093/mtomcs/mfac055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 07/11/2022] [Indexed: 11/12/2022]
Abstract
Organic matter regulates the availability of important trace elements in aquatic and terrestrial ecosystems by acting as a source and container for microbes. To overcome the limitation of trace elements, nitrogen-fixing bacteria, for example, release low-molecular-weight chelators (metallophores), which scavenge the essential cofactors of the nitrogenase, iron and molybdenum, via complexation and subsequent uptake. The formation of metallophores is triggered by limiting conditions, which must be replicated in the laboratory in order to study metallophores as a mediator in metal cycling. While EDTA-based buffer systems for metal cations are well established, there is limited knowledge regarding the buffering of oxoanions such as molybdate in a bacterial growth medium. To mimic the availability of molybdenum in nature under laboratory conditions, this study created a Mo-buffer system for bacterial growth media of the model organisms Azotobacter vinelandii and Frankia sp. CH37. We investigated selected hydroxypyridinones (HPs) as potential molybdenum-chelating agents, determining the amount required for efficient molybdenum complexation by calculating speciation plots of the various candidate complexes in artificial growth media at various pH values. The Mo-maltol system was identified as an ideal, non-toxic molybdenum-buffer system. In the presence of the Mo-maltol system, the growth of Frankia sp. was limited under diazotrophic conditions, whereas A. vinelandii could acquire molybdenum through the release of protochelin and subsequent molybdenum uptake. The study paves the way for unravelling molybdenum recruitment and homeostasis under limiting conditions in bacteria.
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Affiliation(s)
- Jan Frieder Mohr
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Jena, Germany
| | - Sofia Gama
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Jena, Germany
- Department of Analytical Chemistry, Faculty of Chemistry, University of Białystok, Białystok, Poland
| | - Sébastien Roy
- Centre SÈVE, Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Jean-Philippe Bellenger
- Centre SÈVE, Département de Chimie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Winfried Plass
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Jena, Germany
| | - Thomas Wichard
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Jena, Germany
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8
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Soleymani Movahed F, Foo SW, Mori S, Ogawa S, Saito S. Phosphorus-Based Organocatalysis for the Dehydrative Cyclization of N-(2-Hydroxyethyl)amides into 2-Oxazolines. J Org Chem 2021; 87:243-257. [PMID: 34882422 DOI: 10.1021/acs.joc.1c02318] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A metal-free, biomimetic catalytic protocol for the cyclization of N-(2-hydroxyethyl)amides to the corresponding 2-oxazolines (4,5-dihydrooxazoles), promoted by the 1,3,5,2,4,6-triazatriphosphorine (TAP)-derived organocatalyst tris(o-phenylenedioxy)cyclotriphosphazene (TAP-1) has been developed. This approach requires less precatalyst compared to the reported relevant systems, with respect to the phosphorus atom (the maximum turnover number (TON) ∼ 30), and exhibits a broader substrate scope and higher functional-group tolerance, providing the functionalized 2-oxazolines with retention of the configuration at the C(4) stereogenic center of the 2-oxazolines. Widely accessible β-amino alcohols can be used in this approach, and the cyclization of N-(2-hydroxyethyl)amides provides the desired 2-oxazolines in up to 99% yield. The mechanism of the reaction was studied by monitoring the reaction using spectral and analytical methods, whereby an 18O-labeling experiment furnished valuable insights. The initial step involves a stoichiometric reaction between the substrate and TAP-1, which leads to the in situ generation of the catalyst, a catechol cyclic phosphate, as well as to a pyrocatechol phosphate and two possible active intermediates. The dehydrative cyclization was also successfully conducted on the gram scale.
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Affiliation(s)
| | - Siong Wan Foo
- Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Shogo Mori
- Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Saeko Ogawa
- Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
| | - Susumu Saito
- Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.,Research Center for Materials Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan
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