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Abstract
Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R1R2N-O•. The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R1 and R2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R1R2N═O+) or reduced to anions (R1R2N-O-), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C-O bonds, allowing for the thermal generation of C radicals through reversible C-O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.
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Affiliation(s)
- Dirk Leifert
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
| | - Armido Studer
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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Kanoh N, Kawamata-Asano A, Suzuki K, Takahashi Y, Miyazawa T, Nakamura T, Moriya T, Hirano H, Osada H, Iwabuchi Y, Takahashi S. An integrated screening system for the selection of exemplary substrates for natural and engineered cytochrome P450s. Sci Rep 2019; 9:18023. [PMID: 31792277 PMCID: PMC6888865 DOI: 10.1038/s41598-019-54473-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 11/14/2019] [Indexed: 11/26/2022] Open
Abstract
Information about substrate and product selectivity is critical for understanding the function of cytochrome P450 monooxygenases. In addition, comprehensive understanding of changes in substrate selectivity of P450 upon amino acid mutation would enable the design and creation of engineered P450s with desired selectivities. Therefore, systematic methods for obtaining such information are required. Herein, we developed an integrated P450 substrate screening system for the selection of “exemplary” substrates for a P450 of interest. The established screening system accurately selected the known exemplary substrates and also identified previously unknown exemplary substrates for microbial-derived P450s from a library containing sp3-rich synthetic small molecules. Synthetically potent transformations were also found by analyzing the reactions and oxidation products. The screening system was applied to analyze the substrate selectivity of the P450 BM3 mutants F87A and F87A/A330W, which acquired an ability to hydroxylate non-natural substrate steroids regio- and stereoselectively by two amino acid mutations. The distinct transition of exemplary substrates due to each single amino acid mutation was revealed, demonstrating the utility of the established system.
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Affiliation(s)
- Naoki Kanoh
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan. .,Institute of Medicinal Chemistry, Hoshi University, 2-4-1 Ebara, Shinagawa-ku, Tokyo, 142-8501, Japan.
| | - Ayano Kawamata-Asano
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Kana Suzuki
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Yusuke Takahashi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Takeshi Miyazawa
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Takemichi Nakamura
- Molecular Structure Characterization Unit, Technology Platform Division, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Takashi Moriya
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Hiroyuki Hirano
- Chemical Resource Development Research Unit, Technology Platform Division, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Hiroyuki Osada
- Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Chemical Resource Development Research Unit, Technology Platform Division, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Yoshiharu Iwabuchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Shunji Takahashi
- Natural Product Biosynthesis Research Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
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Lambert KM, Stempel ZD, Kiendzior SM, Bartelson AL, Bailey WF. Enhancement of the Oxidizing Power of an Oxoammonium Salt by Electronic Modification of a Distal Group. J Org Chem 2018; 82:11440-11446. [PMID: 28968489 DOI: 10.1021/acs.joc.7b01965] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The multigram preparation and characterization of a novel TEMPO-based oxoammonium salt, 2,2,6,6-tetramethyl-4-(2,2,2-trifluoroacetamido)-1-oxopiperidinium tetrafluoroborate (5), and its corresponding nitroxide (4) are reported. The solubility profile of 5 in solvents commonly used for alcohol oxidations differs substantially from that of Bobbitt's salt, 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate (1). The rates of oxidation of a representative series of primary, secondary, and benzylic alcohols by 1 and 5 in acetonitrile solvent at room temperature have been determined, and oxoammonium salt 5 has been found to oxidize alcohols more rapidly than does 1. The rate of oxidation of meta- and para-substituted benzylic alcohols by either 1 or 5 displays a strong linear correlation to Hammett parameters (r > 0.99) with slopes (ρ) of -2.7 and -2.8, respectively, indicating that the rate-limiting step in the oxidations involves hydride abstraction from the carbinol carbon of the alcohol substrate.
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Affiliation(s)
- Kyle M Lambert
- Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3060, United States
| | - Zachary D Stempel
- Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3060, United States
| | - Sadie M Kiendzior
- Department of Chemistry, University of Saint Joseph , West Hartford, Connecticut 06117-2791, United States
| | - Ashley L Bartelson
- Department of Chemistry, Seton Hill University , Greensburg, Pennsylvania 15601, United States
| | - William F Bailey
- Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3060, United States
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Ro Lee K, Sub Kim C, Subedi L, Oh J, Yeou Kim S, Un Choi S. A New Phenolic Compound from Salix glandulosa. HETEROCYCLES 2018. [DOI: 10.3987/com-18-13892] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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5
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Ng K, Minehan TG. A Single-Flask Synthesis of Morita-Baylis-Hillman Adducts from Ethoxyacetylene and Carbonyl Compounds: Synthesis of Subamolides D and E. Org Lett 2016; 18:4028-31. [PMID: 27490948 DOI: 10.1021/acs.orglett.6b01772] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sequential treatment of (ethoxyethynyl)lithium with aldehydes and/or ketones (2 and 4) and BF3·OEt2 gives rise to β-hydroxyenoates 5 in good to excellent overall yields. Similarly, the combination of 1 (M = Li) and dicarbonyl compounds 6 (X = O) or keto/aldehyde acetals (X = OMe) followed by the addition of a Lewis acid leads to five-, six-, and seven-membered hydroxycycloalkene carboxyates. The utility of this method is demonstrated in the synthesis of the α-alkylidene lactone natural products subamolide D and E.
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Affiliation(s)
- Kevin Ng
- Department of Chemistry and Biochemistry, California State University , Northridge 18111 Nordhoff Street, Northridge, California 91330-8262, United States
| | - Thomas G Minehan
- Department of Chemistry and Biochemistry, California State University , Northridge 18111 Nordhoff Street, Northridge, California 91330-8262, United States
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Jervis J, Hildreth SB, Sheng X, Beers EP, Brunner AM, Helm RF. A metabolomic assessment of NAC154 transcription factor overexpression in field grown poplar stem wood. PHYTOCHEMISTRY 2015; 115:112-20. [PMID: 25771508 DOI: 10.1016/j.phytochem.2015.02.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 12/19/2014] [Accepted: 02/08/2015] [Indexed: 05/24/2023]
Abstract
Several xylem-associated regulatory genes have been identified that control processes associated with wood formation in poplar. Prominent among these are the NAC domain transcription factors (NACs). Here, the putative involvement of Populus NAC154, a co-ortholog of the Arabidopsis gene SND2, was evaluated as a regulator of "secondary" biosynthetic processes in stem internode tissues by interrogating aqueous methanolic extracts from control and transgenic trees. Comprehensive untargeted metabolite profiling was accomplished with a liquid chromatography-mass spectrometry platform that utilized two different chromatographic supports (HILIC and reversed phase) and both positive and negative ionization modes. Evaluation of current and previous year tissues provided datasets for assessing the effects of NAC154 overexpression in wood maturation processes. Phenolic glycoside levels as well as those of oligolignols, sucrose and arginine were modulated with phenotypic and chemotypic traits exhibiting similar trends. Specifically, increased levels of arginine in the NAC154 overexpressing tissues supports a role for the transcription factor in senescence/dormancy-associated processes.
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Affiliation(s)
- Judith Jervis
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - Sherry B Hildreth
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Xiaoyan Sheng
- Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA 24061, USA
| | - Eric P Beers
- Department of Horticulture, Virginia Tech, Blacksburg, VA 24061, USA
| | - Amy M Brunner
- Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA 24061, USA
| | - Richard F Helm
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
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Kim TB, Kim HW, Lee M, Lee HH, Kim SH, Kang SK, Sung SH. Isolation and structure elucidation of (−)-idescarparide, a new spiro compound from Idesia polycarpa. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Carbó López M, Royal G, Philouze C, Chavant PY, Blandin V. Imidazolidinone Nitroxides as Catalysts in the Aerobic Oxidation of Alcohols, en Route to Atroposelective Oxidative Desymmetrization. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402324] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Griffith DR, Botta L, St Denis TG, Snyder SA. Explorations of caffeic acid derivatives: total syntheses of rufescenolide, yunnaneic acids C and D, and studies toward yunnaneic acids A and B. J Org Chem 2013; 79:88-105. [PMID: 24328186 DOI: 10.1021/jo4023167] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Yunnaneic acids A-D, isolated from the roots of Salvia yunnanensis , are hexameric (A and B) and trimeric (C and D) assemblies of caffeic acid that feature an array of synthetically challenging and structurally interesting domains. In addition to being caffeic acid oligomers, yunnaneic acids A and B are formally dimeric and heterodimeric adducts of yunnaneic acids C and D. Herein we report the first total syntheses of yunnaneic acids C and D featuring the formation of their bicyclo[2.2.2]octene cores in a single step from simple precursors via an oxidative dearomatization/Diels-Alder cascade that may have biogenetic relevance. In addition, exploitation of the key intermediate resulting from this cascade reaction has enabled rapid access to the structurally related caffeic acid metabolite rufescenolide through an unexpected Lewis acid-mediated reduction. Finally, we report the results of extensive model studies toward forming the dimeric yunnaneic acids A and B. These explorations indicate that the innate reactivities of the monomeric fragments do not favor spontaneous formation of the desired dimeric linkages. Consequently, enzymatic involvement may be required for the biosynthesis of these more complex family members.
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Affiliation(s)
- Daniel R Griffith
- Department of Chemistry, Columbia University , Havemeyer Hall, 3000 Broadway, New York, New York 10027, United States
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Tran V, Minehan TG. Lewis acid catalyzed intramolecular condensation of ynol ether-acetals. Synthesis of alkoxycycloalkene carboxylates. Org Lett 2012; 14:6100-3. [PMID: 23170869 DOI: 10.1021/ol303026v] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Treatment of ynol ether-tethered dialkyl acetals with catalytic quantities of scandium triflate in CH(3)CN gives rise to five-, six-, and seven-membered alkoxycycloalkene carboxylates in good to excellent yields. Tri- and tetrasubstituted carbocyclic and heterocyclic alkenes may be formed by this method, and the products obtained may serve as useful intermediates for natural product synthesis.
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Affiliation(s)
- Vincent Tran
- Department of Chemistry and Biochemistry, California State University, Northridge 18111 Nordhoff Street, Northridge, California 91330, USA
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Waser M. Asymmetric Oxidations and Reductions. ASYMMETRIC ORGANOCATALYSIS IN NATURAL PRODUCT SYNTHESES 2012:137-148. [DOI: 10.1007/978-3-7091-1163-5_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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Hayashi M, Shibuya M, Iwabuchi Y. Oxidative Conversion of Silyl Enol Ethers to α,β-Unsaturated Ketones Employing Oxoammonium Salts. Org Lett 2011; 14:154-7. [DOI: 10.1021/ol2029417] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masaki Hayashi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aobayama, Sendai 980-8578, Japan, and Process Technology Research Laboratories, Daiichi Sankyo Co., Ltd., 1-12-1 Shinomiya, Hiratsuka, Kanagawa 254-0014, Japan
| | - Masatoshi Shibuya
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aobayama, Sendai 980-8578, Japan, and Process Technology Research Laboratories, Daiichi Sankyo Co., Ltd., 1-12-1 Shinomiya, Hiratsuka, Kanagawa 254-0014, Japan
| | - Yoshiharu Iwabuchi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aobayama, Sendai 980-8578, Japan, and Process Technology Research Laboratories, Daiichi Sankyo Co., Ltd., 1-12-1 Shinomiya, Hiratsuka, Kanagawa 254-0014, Japan
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Rajca A, Shiraishi K, Boratyński PJ, Pink M, Miyasaka M, Rajca S. Oxidation of Annelated Diarylamines: Analysis of Reaction Pathways to Nitroxide Diradical and Spirocyclic Products. J Org Chem 2011; 76:8447-57. [DOI: 10.1021/jo2017923] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Kouichi Shiraishi
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | | | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Makoto Miyasaka
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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Tebben L, Studer A. Nitroxides: applications in synthesis and in polymer chemistry. Angew Chem Int Ed Engl 2011; 50:5034-68. [PMID: 21538729 DOI: 10.1002/anie.201002547] [Citation(s) in RCA: 505] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Indexed: 01/23/2023]
Abstract
This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.
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Affiliation(s)
- Ludger Tebben
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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Shibuya M, Osada Y, Sasano Y, Tomizawa M, Iwabuchi Y. Highly Efficient, Organocatalytic Aerobic Alcohol Oxidation. J Am Chem Soc 2011; 133:6497-500. [DOI: 10.1021/ja110940c] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masatoshi Shibuya
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama 6-3, Sendai 980-8578, Japan
| | - Yuji Osada
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama 6-3, Sendai 980-8578, Japan
| | - Yusuke Sasano
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama 6-3, Sendai 980-8578, Japan
| | - Masaki Tomizawa
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama 6-3, Sendai 980-8578, Japan
| | - Yoshiharu Iwabuchi
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama 6-3, Sendai 980-8578, Japan
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Snyder SA, Kontes F. Synthetic Studies of Biomimetic Diels-Alder Processes toward the Helicterin Family of Natural Products. Isr J Chem 2011. [DOI: 10.1002/ijch.201100004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Nagasawa T, Shimada N, Torihata M, Kuwahara S. Enantioselective total synthesis of idesolide via NaHCO3-promoted dimerization. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.05.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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