1
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Johny M, Rajendar G. Effective In Situ Alkoxide Trapping by TMSX in the Presence of TPP Catalyst in Glycidol Acetal Rearrangements. J Org Chem 2024; 89:7036-7046. [PMID: 38716502 DOI: 10.1021/acs.joc.4c00408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
This study demonstrates a nucleophile-catalyzed, trimethylsilyl halide-promoted rearrangement reaction of glycidol acetals to form halogenated cyclic acetals. The acetal group has been activated selectively in the presence of trimethylsilyl cation, which is used as in situ-generated alkoxide trapping reagent. Nucleophilic chloride and bromide ions participate in addition reactions with epoxides predominantly via SN1-type epoxide opening, while non-nucleophilic iodide and triflate ions induce a positive charge at the epoxide carbon. A systematic investigation of acetal-initiated polyene cyclization of epoxy polyenes has been conducted using bicyclic epoxonium ions as transient intermediates. Unfavorable orbital orientation and other stereoelectronic factors hinder the much-anticipated polyene cyclizations. The potential of this method has been showcased through its application in the total synthesis of parvistone A, a chlorinated styryllactone.
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Affiliation(s)
- Meera Johny
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala 695551, India
| | - Goreti Rajendar
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala 695551, India
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2
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Lavigne C, Gomes G, Pollice R, Aspuru-Guzik A. Guided discovery of chemical reaction pathways with imposed activation. Chem Sci 2022; 13:13857-13871. [PMID: 36544742 PMCID: PMC9710306 DOI: 10.1039/d2sc05135d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 11/09/2022] [Indexed: 11/12/2022] Open
Abstract
Computational power and quantum chemical methods have improved immensely since computers were first applied to the study of reactivity, but the de novo prediction of chemical reactions has remained challenging. We show that complex reaction pathways can be efficiently predicted in a guided manner using chemical activation imposed by geometrical constraints of specific reactive modes, which we term imposed activation (IACTA). Our approach is demonstrated on realistic and challenging chemistry, such as a triple cyclization cascade involved in the total synthesis of a natural product, a water-mediated Michael addition, and several oxidative addition reactions of complex drug-like molecules. Notably and in contrast with traditional hand-guided computational chemistry calculations, our method requires minimal human involvement and no prior knowledge of the products or the associated mechanisms. We believe that IACTA will be a transformational tool to screen for chemical reactivity and to study both by-product formation and decomposition pathways in a guided way.
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Affiliation(s)
- Cyrille Lavigne
- Department of Computer Science, University of Toronto214 College St.TorontoOntarioM5T 3A1Canada
| | - Gabe Gomes
- Department of Computer Science, University of Toronto214 College St.TorontoOntarioM5T 3A1Canada,Chemical Physics Theory Group, Department of Chemistry, University of Toronto80 St George StTorontoOntarioM5S 3H6Canada
| | - Robert Pollice
- Department of Computer Science, University of Toronto214 College St.TorontoOntarioM5T 3A1Canada,Chemical Physics Theory Group, Department of Chemistry, University of Toronto80 St George StTorontoOntarioM5S 3H6Canada
| | - Alán Aspuru-Guzik
- Department of Computer Science, University of Toronto214 College St.TorontoOntarioM5T 3A1Canada,Chemical Physics Theory Group, Department of Chemistry, University of Toronto80 St George StTorontoOntarioM5S 3H6Canada,Department of Chemical Engineering & Applied Chemistry, University of Toronto200 College St.OntarioM5S 3E5Canada,Department of Materials Science & Engineering, University of Toronto184 College St.OntarioM5S 3E4Canada,Vector Institute for Artificial Intelligence661 University Ave Suite 710TorontoOntarioM5G 1M1Canada,Lebovic Fellow, Canadian Institute for Advanced Research (CIFAR)661 University AveTorontoOntarioM5GCanada
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3
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Chen D, Jones EV, Williams CW, Huynh TN, McPhail TC, France S. Intramolecular, Interrupted Homo‐Nazarov Cascade Biscyclizations to Angular (Hetero)Aryl‐Fused Polycycles. Chemistry 2022; 28:e202201368. [DOI: 10.1002/chem.202201368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Indexed: 11/09/2022]
Affiliation(s)
- Doris Chen
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
| | - Elizabeth V. Jones
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
| | - Corey W. Williams
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
| | - Tan‐Khang N. Huynh
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
| | - Tristan C. McPhail
- School of Chemical and Biomolecular Engineering Georgia Institute of Technology Atlanta Georgia 30332 USA
| | - Stefan France
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta Georgia 30332 USA
- Petit Institute for Bioengineering and Bioscience Georgia Institute of Technology Atlanta Georgia 30332 USA
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4
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Martin ML, Boyer A. Controlling Selectivity in the Synthesis of
Z
‐α,β‐Unsaturated Amidines by Tuning the
N
‐Sulfonyl Group in a Rhodium(II) Catalyzed 1,2‐H Shift. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Matthew L. Martin
- School of Chemistry University of Glasgow Joseph Black Building G12 8QQ Glasgow Scotland
| | - Alistair Boyer
- School of Chemistry University of Glasgow Joseph Black Building G12 8QQ Glasgow Scotland
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5
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Feilner JM, Plangger I, Wurst K, Magauer T. Bifunctional Polyene Cyclizations: Synthetic Studies on Pimarane Natural Products. Chemistry 2021; 27:12410-12421. [PMID: 34213030 PMCID: PMC8457131 DOI: 10.1002/chem.202101926] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Indexed: 11/10/2022]
Abstract
Polyene cyclizations generate molecular complexity from a linear polyene in a single step. While methods to initiate these cyclizations have been continuously expanded and improved over the years, the majority of polyene substrates are still limited to simple alkyl-substituted alkenes. In this study, we took advantage of the unique reactivity of higher-functionalized bifunctional alkenes. The realization of a polyene tetracyclization of a dual nucleophilic aryl enol ether involving a transannular endo-termination step enabled the total synthesis of the tricyclic diterpenoid pimara-15-en-3α-8α-diol. The highly flexible and modular route allowed for the preparation of a diverse library of cyclization precursors specifically designed for the total synthesis of the tetracyclic nor-diterpenoid norflickinflimiod C. The tetracyclization of three diversely substituted allenes enabled access to complex pentacyclic products and provided a detailed insight into the underlying reaction pathways.
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Affiliation(s)
- Julian M. Feilner
- Institute of Organic Chemistry and Center for Molecular BiosciencesLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
| | - Immanuel Plangger
- Institute of Organic Chemistry and Center for Molecular BiosciencesLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical ChemistryLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
| | - Thomas Magauer
- Institute of Organic Chemistry and Center for Molecular BiosciencesLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
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6
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Liang XT, Sun BC, Liu C, Li YH, Zhang N, Xu QQ, Zhang ZC, Han YX, Chen JH, Yang Z. Asymmetric Total Synthesis of (-)-Spirochensilide A, Part 1: Diastereoselective Synthesis of the ABCD Ring and Stereoselective Total Synthesis of 13( R)-Demethyl Spirochensilide A. J Org Chem 2021; 86:2135-2157. [PMID: 33433196 DOI: 10.1021/acs.joc.0c02494] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A concise and diastereoselective construction of the ABCD ring system of spirochensilide A is described. The key steps of this synthesis are a semipinacol rearrangement reaction to stereoselectively construct the AB ring system bearing two vicinal quaternary chiral centers and a Co-mediated Pauson-Khand reaction to form the spiro-based bicyclic CD ring system. This chemistry leads to the stereoselective synthesis of 13(R)-demethyl spirochensilide A, paving the way for the first asymmetric total synthesis of (-)-spirochensilide A.
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Affiliation(s)
- Xin-Ting Liang
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Bao-Chuan Sun
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Chang Liu
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Yuan-He Li
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Nan Zhang
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Qian-Qian Xu
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Zhong-Chao Zhang
- Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Yi-Xin Han
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Jia-Hua Chen
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China
| | - Zhen Yang
- State Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for Molecular Science (BNLMS), College of Chemistry, Peking University, Beijing 100871, China.,Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China.,Shenzhen Bay Laboratory, Shenzhen 518055, China
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7
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Feilner JM, Wurst K, Magauer T. A Transannular Polyene Tetracyclization for Rapid Construction of the Pimarane Framework. Angew Chem Int Ed Engl 2020; 59:12436-12439. [PMID: 32167649 PMCID: PMC7383491 DOI: 10.1002/anie.202003127] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Indexed: 01/27/2023]
Abstract
Polyene cyclizations are one of the most powerful and fascinating chemical transformations to rapidly generate molecular complexity. However, cyclizations employing heteroatom-substituted polyenes are rare. Described here is the tetracyclization of a dual nucleophilic aryl enol ether involving an unprecedented transannular endo-termination step. In this transformation, five stereocenters, two of which are quaternary, four carbon-carbon bonds, and four six-membered rings are formed from a readily available cyclization precursor. The realization of this cyclization enabled short synthetic access to the tricyclic diterpenoid pimara-15-en-3α-8α-diol.
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Affiliation(s)
- Julian M. Feilner
- Institute of Organic Chemistry and Center for Molecular BiosciencesLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical ChemistryLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
| | - Thomas Magauer
- Institute of Organic Chemistry and Center for Molecular BiosciencesLeopold-Franzens-University InnsbruckInnrain 80–826020InnsbruckAustria
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8
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Feilner JM, Wurst K, Magauer T. A Transannular Polyene Tetracyclization for Rapid Construction of the Pimarane Framework. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202003127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Julian M. Feilner
- Institute of Organic Chemistry and Center for Molecular Biosciences Leopold-Franzens-University Innsbruck Innrain 80–82 6020 Innsbruck Austria
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical Chemistry Leopold-Franzens-University Innsbruck Innrain 80–82 6020 Innsbruck Austria
| | - Thomas Magauer
- Institute of Organic Chemistry and Center for Molecular Biosciences Leopold-Franzens-University Innsbruck Innrain 80–82 6020 Innsbruck Austria
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9
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Quilez Del Moral JF, Domingo V, Pérez Á, Martínez Andrade KA, Enríquez L, Jaraiz M, López-Pérez JL, Barrero AF. Mimicking Halimane Synthases: Monitoring a Cascade of Cyclizations and Rearrangements from Epoxypolyprenes. J Org Chem 2019; 84:13764-13779. [PMID: 31559826 DOI: 10.1021/acs.joc.9b01996] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We have developed and rationalized a biomimetic transformation mimicking halimane synthases based on a Lewis acid-catalyzed cascade of cyclizations and rearrangements of epoxypolyprenes. Two rings, three stereogenic centers, and a new double bond were generated in a single chemical operation. Based on this cascade transformation, we achieved a unified strategy toward the stereoselective total syntheses of halimene-type terpenoids and analogues as a proof-of-concept study. This method has been applied to the rapid synthesis of diterpene isotuberculosinol, a virulence factor of Mycobacterium tuberculosis as a representative example.
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Affiliation(s)
- José F Quilez Del Moral
- Department of Organic Chemistry, Institute of Biotechnology , University of Granada , 18071 Granada , Spain
| | - Victoriano Domingo
- Department of Organic Chemistry, Institute of Biotechnology , University of Granada , 18071 Granada , Spain
| | - Álvaro Pérez
- Department of Organic Chemistry, Institute of Biotechnology , University of Granada , 18071 Granada , Spain
| | - Kevin A Martínez Andrade
- Department of Organic Chemistry, Institute of Biotechnology , University of Granada , 18071 Granada , Spain
| | - Lourdes Enríquez
- Department of Electronics , University of Valladolid , 47011 Valladolid , Spain
| | - Martín Jaraiz
- Department of Electronics , University of Valladolid , 47011 Valladolid , Spain
| | - José Luis López-Pérez
- Department of Pharmaceutical Sciences, IBSAL-CIETUS , University of Salamanca , 37007 Salamanca , Spain.,Department of Pharmacology, Faculty of Medicine , University of Panama , 3366 Panama , Republic of Panama
| | - Alejandro F Barrero
- Department of Organic Chemistry, Institute of Biotechnology , University of Granada , 18071 Granada , Spain
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10
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Abstract
The first total synthesis of parvifloron F, a bioactive highly oxidized abietane diterpene, was achieved. The abietane skeleton was constructed by Lewis acid promoted cyclization. Preliminary structure-activity relationship correlations were established for the synthetic intermediates against human tumor cell lines. Certain compounds showed unique selective antiproliferative activity against triple-negative breast cancer. The oxidation level of the abietane ring affected the selectivity.
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Affiliation(s)
- Yohei Saito
- School of Pharmaceutical Sciences, College of Medical, Pharmaceutical and Health Science, Kanazawa University , Kanazawa, 920-1192, Japan
| | - Masuo Goto
- Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7568, United States
| | - Kyoko Nakagawa-Goto
- School of Pharmaceutical Sciences, College of Medical, Pharmaceutical and Health Science, Kanazawa University , Kanazawa, 920-1192, Japan.,Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599-7568, United States
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11
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Harmalkar DS, Mali JR, Sivaraman A, Choi Y, Lee K. Schweinfurthins A–Q: isolation, synthesis, and biochemical properties. RSC Adv 2018; 8:21191-21209. [PMID: 35539907 PMCID: PMC9080957 DOI: 10.1039/c8ra02872a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 05/21/2018] [Indexed: 02/04/2023] Open
Abstract
Stilbene analogues have shown remarkable structural diversity constituting simple or tangled structures, which have attracted the synthetic as well as the medicinal chemistry communities. Schweinfurthins are a family of prenylated/geranylated/farnesylated stilbenes that are isolated from an African plant belonging to the Macaranga species. These compounds have displayed potency towards central nervous system, renal and breast cancer cell lines. Specifically, these compounds have been found to be potent and selective inhibitors of cell growth in the National Cancer Institute's 60 cell-line screen. In this review article, we described the isolation, synthesis, and biochemical properties of schweinfurthins. An overview of the isolation, synthesis, and biochemical properties of the stilbene-based natural products schweinfurthins A–Q (1999–2017).![]()
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Affiliation(s)
| | | | - Aneesh Sivaraman
- College of Pharmacy
- Dongguk University-Seoul
- Goyang
- Republic of Korea
| | - Yongseok Choi
- Department of Biotechnology
- Korea University
- Seoul
- Republic of Korea
| | - Kyeong Lee
- College of Pharmacy
- Dongguk University-Seoul
- Goyang
- Republic of Korea
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12
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Bartels F, Hong YJ, Ueda D, Weber M, Sato T, Tantillo DJ, Christmann M. Bioinspired synthesis of pentacyclic onocerane triterpenoids. Chem Sci 2017; 8:8285-8290. [PMID: 29619174 PMCID: PMC5858022 DOI: 10.1039/c7sc03903d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 10/14/2017] [Indexed: 01/23/2023] Open
Abstract
The first chemical synthesis of pentacyclic onocerane triterpenoids (+)-cupacinoxepin and (+)-onoceranoxide is described.
The first chemical synthesis of pentacyclic onocerane triterpenoids has been achieved. A putative biomimetic tricyclization cascade is employed to forge a fused decalin-/oxepane ring system. The synthetic route proceeds to (+)-cupacinoxepin in seven steps and to (+)-onoceranoxide in eight steps in the longest linear sequence, when starting from geranyl chloride and (+)-sclareolide. The bioinspired epoxypolyene cyclization is supported by computational and enzymatic studies.
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Affiliation(s)
- Florian Bartels
- Institute of Chemistry and Biochemistry , Freie Universität Berlin , Takustraße 3 , 14195 Berlin , Germany .
| | - Young J Hong
- Department of Chemistry , University of California-Davis , Davis , California 95616 , USA .
| | - Daijiro Ueda
- Department of Applied Biological Chemistry , Graduate School of Science and Technology , Niigata University , Ikarashi 2-8050, Nishi-ku , Niigata 950-2181 , Japan .
| | - Manuela Weber
- Institute of Chemistry and Biochemistry , Freie Universität Berlin , Takustraße 3 , 14195 Berlin , Germany .
| | - Tsutomu Sato
- Department of Applied Biological Chemistry , Graduate School of Science and Technology , Niigata University , Ikarashi 2-8050, Nishi-ku , Niigata 950-2181 , Japan .
| | - Dean J Tantillo
- Department of Chemistry , University of California-Davis , Davis , California 95616 , USA .
| | - Mathias Christmann
- Institute of Chemistry and Biochemistry , Freie Universität Berlin , Takustraße 3 , 14195 Berlin , Germany .
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13
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Sarkar MR, Lee JHZ, Bell SG. The Oxidation of Hydrophobic Aromatic Substrates by Using a Variant of the P450 Monooxygenase CYP101B1. Chembiochem 2017; 18:2119-2128. [PMID: 28868671 DOI: 10.1002/cbic.201700316] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Indexed: 11/10/2022]
Abstract
The cytochrome P450 monooxygenase CYP101B1, from a Novosphingobium bacterium is able to bind and oxidise aromatic substrates but at a lower activity and efficiency than norisoprenoids and monoterpenoid esters. Histidine 85 of CYP101B1 aligns with tyrosine 96 of CYP101A1, which, in the latter enzyme forms the only hydrophilic interaction with its substrate, camphor. The histidine residue of CYP101B1 was mutated to phenylalanine with the aim of improving the activity of the enzyme for hydrophobic substrates. The H85F mutant lowered the binding affinity and activity of the enzyme for β-ionone and altered the oxidation selectivity. This variant also showed enhanced affinity and activity towards alkylbenzenes, styrenes and methylnaphthalenes. For example the rate of product formation for acenaphthene oxidation was improved sixfold to 245 nmol per nmol CYP per min. Certain disubstituted naphthalenes and substrates, such as phenylcyclohexane and biphenyls, were oxidised with lower activity by the H85F variant. Variants at H85 (A and G) designed to introduce additional space into the active site so as to accommodate these larger substrates did not improve the oxidation activity. As the H85F mutant of CYP101B1 improved the oxidation of hydrophobic substrates, this residue is likely to be in the substrate binding pocket or the access channel of the enzyme. The side chain of the histidine might interact with the carbonyl groups of the favoured norisoprenoid substrates of CYP101B1.
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Affiliation(s)
- Md Raihan Sarkar
- Department of Chemistry, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Joel H Z Lee
- Department of Chemistry, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Stephen G Bell
- Department of Chemistry, University of Adelaide, Adelaide, SA, 5005, Australia
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14
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Zweig JE, Kim DE, Newhouse TR. Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis. Chem Rev 2017; 117:11680-11752. [PMID: 28525261 DOI: 10.1021/acs.chemrev.6b00833] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
First-row transition-metal-mediated reactions constitute an important and growing area of research due to the low cost, low toxicity, and exceptional synthetic versatility of these metals. Currently, there is considerable effort to replace existing precious-metal-catalyzed reactions with first-row analogs. More importantly, there are a plethora of unique transformations mediated by first-row metals, which have no classical second- or third-row counterpart. Herein, the application of first-row metal-mediated methods to the total synthesis of natural products is discussed. This Review is intended to highlight strategic uses of these metals to realize efficient syntheses and highlight the future potential of these reagents and catalysts in organic synthesis.
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Affiliation(s)
- Joshua E Zweig
- Department of Chemistry, Yale University , 275 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Daria E Kim
- Department of Chemistry, Yale University , 275 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Timothy R Newhouse
- Department of Chemistry, Yale University , 275 Prospect Street, New Haven, Connecticut 06520-8107, United States
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15
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Bonrath W, Pressel Y, Schütz J, Ferfecki E, Topp KD. Aldol Condensations Catalyzed by Basic Anion-Exchange Resins. ChemCatChem 2016. [DOI: 10.1002/cctc.201600867] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Werner Bonrath
- DSM Nutritional Products; Research and Development, Process Research; P.O. Box 2676 CH-4002 Basel Switzerland
| | - Yann Pressel
- DSM Nutritional Products; Research and Development, Process Research; P.O. Box 2676 CH-4002 Basel Switzerland
| | - Jan Schütz
- DSM Nutritional Products; Research and Development, Process Research; P.O. Box 2676 CH-4002 Basel Switzerland
| | - Erich Ferfecki
- Dow Deutschland Anlagengesellschaft GmbH; Industriestr. 1 77836 Rheinmünster Germany
| | - Klaus-Dieter Topp
- Dow Deutschland Vertriebs GmbH & Co. OHG; Am Kronberger Hang 4 65824 Schwalbach Germany
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16
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Hall EA, Sarkar MR, Lee JHZ, Munday SD, Bell SG. Improving the Monooxygenase Activity and the Regio- and Stereoselectivity of Terpenoid Hydroxylation Using Ester Directing Groups. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01882] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Emma A. Hall
- Department
of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Md. Raihan Sarkar
- Department
of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Joel H. Z. Lee
- Department
of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Samuel D. Munday
- Department
of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Stephen G. Bell
- Department
of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
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17
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Tian Y, Xu X, Zhang L, Qu J. Tetraphenylphosphonium Tetrafluoroborate/1,1,1,3,3,3-Hexafluoroisopropanol (Ph4PBF4/HFIP) Effecting Epoxide-Initiated Cation–Olefin Polycyclizations. Org Lett 2016; 18:268-71. [DOI: 10.1021/acs.orglett.5b03438] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yan Tian
- State Key Laboratory
and
Institute of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China
| | - Xin Xu
- State Key Laboratory
and
Institute of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China
| | - Lin Zhang
- State Key Laboratory
and
Institute of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China
| | - Jin Qu
- State Key Laboratory
and
Institute of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, China
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18
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Suzuki K, Yamakoshi H, Nakamura S. Construction of Bridged Polycyclic Systems by Polyene Cyclization. Chemistry 2015; 21:17605-9. [DOI: 10.1002/chem.201503969] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 01/06/2023]
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19
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Justicia J, Jiménez T, Miguel D, Contreras-Montoya R, Chahboun R, Álvarez-Manzaneda E, Collado-Sanz D, Cárdenas DJ, Cuerva JM. Titanocene(III)-Catalyzed 6-exoVersus 7-endoCyclizations of Epoxypolyprenes: Efficient Control and Synthesis of Versatile Terpenic Building Blocks. Chemistry 2013; 19:14484-95. [DOI: 10.1002/chem.201302575] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Indexed: 11/11/2022]
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20
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Synthesis of highly strained terpenes by non-stop tail-to-head polycyclization. Nat Chem 2012; 4:915-20. [PMID: 23089866 DOI: 10.1038/nchem.1458] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 08/14/2012] [Indexed: 11/09/2022]
Abstract
Non-stop carbocationic polycyclizations of isoprenoids have been called the most complex chemical reactions occurring in nature. We describe a strategy for the initiation of tail-to-head polycyclization that relies on the sequestration of the counteranion away from the carbocation, which allows full propagation of the cationic charge. If the anion is mobile, Coulombic forces hold this species in close proximity to the carbocation and cause preemptive termination through elimination. Anion sequestration is crucial for effecting the biomimetic synthesis of complex and unstable terpenes, including the highly strained funebrenes. This study illustrates the deleterious role of the counterion in tail-to-head carbocationic polycyclization reactions, which to the best of our knowledge has not been rigorously explored. These observations are also expected to find use in the design and control of cationic polycyclization along biosynthetic pathways that have previously been inaccessible in bulk solvent.
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21
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Prakash GKS, Mathew T, Olah GA. Gallium(III) triflate: an efficient and a sustainable Lewis acid catalyst for organic synthetic transformations. Acc Chem Res 2012; 45:565-77. [PMID: 22148160 DOI: 10.1021/ar2002039] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Green chemical processes play a crucial role in sustainable development, and efficient recyclable catalysts that can be conveniently applied in various chemical reactions are the key elements for the development of sustainable synthetic processes. Many organic transformations rely on Lewis and Brønsted acid catalysts, and such molecules have been widely studied in organic synthesis. Over the years, researchers have looked for Lewis acid catalysts that provide high selectivity and high turnover frequency but are also stable in aqueous media and recoverable. Since the first preparation of trifluoromethanesulfonic acid by Hazeldine (triflic acid, HOTf), researchers have synthesized and used numerous metal triflates in a variety of organic reactions. Even though the rare earth metal triflates have played a major role in these studies, the majority of rare earth triflates lack one or more of the primary properties of sustainable catalysts: low cost and easy availability of the metals, easy preparation of triflates, aqueous/thermal stability, recyclability, and catalytic efficiency. In this Account, we describe the synthetic applications of Ga(OTf)(3) and its advantages over similar catalysts. Ga(OTf)(3) can be conveniently prepared from gallium metal or gallium chloride in excess of trifluoromethanesulfonic acid (triflic acid) under reflux. Among many Lewis acid catalysts recently studied, Ga(OTf)(3) is water tolerant and soluble and requires very low catalyst loading to drive various acid-catalyzed reactions including Friedel-Crafts alkylation, hydroxyalkylation, and acylation selectively and efficiently. In many reactions Ga(OTf)(3) demonstrated high chemo- and regioselectivity, high yields, excellent stability, and recyclability. We successfully synthesized many biologically active heterocycles and their fluoroanalogs under mild conditions. Many challenging reactions such as the ketonic Strecker reactions proceed efficiently via Ga(OTf)(3) catalysis. Because it is stable in water, this catalyst provides the opportunity to study substrates and develop new synthetic protocols in aqueous media, significantly reducing the production of hazardous waste from organic solvents and toxic catalyst systems.
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Affiliation(s)
- G. K. Surya Prakash
- Donald P. and Katherine B. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, 837 Bloom Walk, Los Angeles, California 90089-1661, United States
| | - Thomas Mathew
- Donald P. and Katherine B. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, 837 Bloom Walk, Los Angeles, California 90089-1661, United States
| | - George A. Olah
- Donald P. and Katherine B. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, 837 Bloom Walk, Los Angeles, California 90089-1661, United States
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22
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Abstract
With increasing environmental concerns, the need for environmentally friendly organic synthesis has gained increased importance. In this regard, bismuth(III) compounds are especially attractive as "green" reagents and catalysts for organic synthesis. Bismuth(III) compounds are remarkably nontoxic, relatively air and moisture stable, and easy to handle. The contributions from our laboratory in the last 5 years in the field of applications of bismuth(III) compounds as catalysts are presented.
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23
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Boone MA, Tong R, McDonald FE, Lense S, Cao R, Hardcastle KI. Biomimetic Syntheses from Squalene-Like Precursors: Synthesis of ent-Abudinol B and Reassessment of the Structure of Muzitone. J Am Chem Soc 2010; 132:5300-8. [DOI: 10.1021/ja1006806] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthew A. Boone
- Department of Chemistry, Emory University, Atlanta, Georgia 30322
| | - Rongbiao Tong
- Department of Chemistry, Emory University, Atlanta, Georgia 30322
| | | | - Sheri Lense
- Department of Chemistry, Emory University, Atlanta, Georgia 30322
| | - Rui Cao
- Department of Chemistry, Emory University, Atlanta, Georgia 30322
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24
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Mente NR, Neighbors JD, Wiemer DF. BF3 x Et2O-mediated cascade cyclizations: synthesis of schweinfurthins F and G. J Org Chem 2008; 73:7963-70. [PMID: 18795788 DOI: 10.1021/jo800951q] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The total synthesis of the natural stilbene (+)-schweinfurthin G (8) has been accomplished through a sequence based on an efficient cationic cascade cyclization. This cascade process is initiated by Lewis acid promoted ring opening of an epoxide and terminated through a novel reaction with a phenolic oxygen "protected" as its MOM ether. Several Lewis acids have been examined for their ability to induce this new reaction, and BF3 x Et2O was found to be the most effective. The only major byproduct under these conditions was one where the expected secondary alcohol was found as its MOM ether derivative (e.g., 30). While this byproduct could be converted to the original target compound through hydrolysis, it also could be employed as a protected alcohol to allow preparation of a benzylic phosphonate (43) without dehydration of the secondary alcohol. The resulting phosphonate was employed in a Horner-Wadsworth-Emmons condensation with an aldehyde representing the right half of the target compounds, an approach complementary to previous studies based on condensation of a right-half phosphonate and a left-half aldehyde.
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Affiliation(s)
- Nolan R Mente
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242-1294, USA
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25
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Tsangarakis C, Raptis C, Arkoudis E, Stratakis M. Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols. Adv Synth Catal 2008. [DOI: 10.1002/adsc.200800180] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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27
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Zhao JF, Zhao YJ, Loh TP. Indium tribromide-promoted arene-terminated epoxy olefin cyclization. Chem Commun (Camb) 2008:1353-5. [DOI: 10.1039/b718337b] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Winne JM, De Clercq PJ, Milanesio M, Pattison P, Viterbo D. Nonenzymic polycyclisation of analogues of oxidosqualene with a preformed C-ring. Org Biomol Chem 2008; 6:1918-25. [DOI: 10.1039/b801670d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Watanabe Y, Laschat S, Budde M, Affolter O, Shimada Y, Urlacher VB. Oxidation of acyclic monoterpenes by P450 BM-3 monooxygenase: influence of the substrate E/Z-isomerism on enzyme chemo- and regioselectivity. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.06.104] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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30
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Tong R, Valentine JC, McDonald FE, Cao R, Fang X, Hardcastle KI. Total Syntheses of Durgamone, Nakorone, and Abudinol B via Biomimetic Oxa- and Carbacyclizations. J Am Chem Soc 2007; 129:1050-1. [PMID: 17263384 DOI: 10.1021/ja068826+] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rongbiao Tong
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
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31
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Lacey JR, Anzalone PW, Duncan CM, Hackert MJ, Mohan RS. A study of epoxyolefin cyclizations catalyzed by bismuth trifluoromethanesulfonate and other metal triflates. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.10.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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32
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Reddy PG, Baskaran S. Epoxide-initiated cationic cyclization of azides: a novel method for the stereoselective construction of 5-hydroxymethyl azabicyclic compounds and application in the stereo- and enantioselective total synthesis of (+)- and (-)-indolizidine 167B and 209D. J Org Chem 2004; 69:3093-101. [PMID: 15104448 DOI: 10.1021/jo035258x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel and general method has been developed for the stereoselective construction of 5-hydroxymethyl azabicyclic ring skeletons based on epoxide-initiated cationic cyclization of azides. The key cyclization reaction was systematically studied with the model compound, 3-(1-oxa-spiro[2.4]hept-4-yl)propyl azide 3a, and EtAlCl(2) was found to be an ideal choice as the catalyst. The generality of this transformation was further tested with different ring sizes, where six- and seven-membered epoxyazides 3b,c underwent smooth cyclization to give 5-hydroxymethyl azepine 4b and 5-hydroxymethyl azocine 4c, respectively, as a single detectable diastereomer. This novel methodology was elegantly applied in the stereoselective total synthesis of indolizidine alkaloids 167B and 209D. Further, the enantioselective total synthesis of natural and unnatural indolizidine alkaloids 167B and 209D was accomplished by using Sharpless asymmetric dihydroxylation as a key step.
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Affiliation(s)
- P Ganapati Reddy
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai-600036, India
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33
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An efficient asymmetric synthesis of key intermediates in the synthesis of aphanorphine and eptazocine. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0957-4166(03)00117-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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34
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Reddy PG, Varghese B, Baskaran S. Epoxide-initiated electrophilic cyclization of azides: a novel route for the stereoselective construction of azabicyclic ring systems and total synthesis of (+/-)-indolizidine 167B and 209D. Org Lett 2003; 5:583-5. [PMID: 12583775 DOI: 10.1021/ol027563v] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] A novel and general method for the stereoselective construction of 5-hydroxymethyl azabicyclic ring skeletons based on epoxide initiated electrophilic cyclization of azides has been developed and applied in the synthesis of (+/-)-indolizidine 167B and 209D with an overall yield of 16.5% and 17.8%, respectively. The efficiency of this methodology is further exemplified in the synthesis of azepine skeleton via tandem cation-olefin-azide cyclization.
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Affiliation(s)
- P Ganapati Reddy
- Department of Chemistry, Indian Institute of Technology, Madras, Chennai-600036, India
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35
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Synthesis of (±)-isoretronecanol, (±)-curassanecine, (±)-heliotridane, (±)-tashiromine and (±)-5-epitashiromine via α-(N-carbamoyl)alkylcuprate chemistry. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)01835-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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36
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Fouillet CC, Mareda J. Protonated cyclopropane as an intermediate in cation–olefin cyclizations. Ab initio and density functional theory investigations. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(01)00808-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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37
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Barrero AF, Cuerva JM, Alvarez-Manzaneda E, Oltra J, Chahboun R. First synthesis of achilleol A using titanium(III) chemistry. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)00358-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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38
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FeCl3 and ZrCl4 regiochemically controlled biomimetic-like cyclizations of simple isoprenoid epoxyolefins. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)00394-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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39
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Zoretic PA, Fang H, Ribeiro AA. Application of a Radical Methodology toward the Synthesis of d,l-5alpha-Pregnanes and Related Steroids: A Stereoselective Radical Cascade Approach. J Org Chem 1998; 63:7213-7217. [PMID: 11672362 DOI: 10.1021/jo980518+] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A stereoselective radical cascade cyclization to 5alpha-pregnanes is presented. Oxidative free radical cyclization of an appropriately substituted chloro cyano ester polyene was used to introduce the all trans stereochemistry in the steroid nucleus. The cyano group was utilized to introduce a C-8beta angular hydrogen, while the chloro ester moiety served as an entry to the geminal hydrogens at C-4.
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Affiliation(s)
- Phillip A. Zoretic
- Duke NMR Spectroscopy Center and Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710
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40
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Sen SE, Roach SL, Smith SM, Zhang YZ. Ferric chloride, an efficient promoter of cationic polyene cyclizations. Tetrahedron Lett 1998. [DOI: 10.1016/s0040-4039(98)00738-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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41
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42
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Sen SE, Zhang YZ, Roach SL. Zeolite-Mediated Cyclization of an Epoxide-Containing Polyene. J Org Chem 1996. [DOI: 10.1021/jo960745g] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stephanie E. Sen
- Department of Chemistry, Indiana University−Purdue University at Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana 46202
| | - Yan zhi Zhang
- Department of Chemistry, Indiana University−Purdue University at Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana 46202
| | - Steven L. Roach
- Department of Chemistry, Indiana University−Purdue University at Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana 46202
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43
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Kuthan J, Šebek P, Böhm S. New Developments in the Chemistry of Pyrans. ADVANCES IN HETEROCYCLIC CHEMISTRY 1995. [DOI: 10.1016/s0065-2725(08)60421-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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44
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Selective termination of a polyene cyclization by an internally situated allylsilane group. Tetrahedron Lett 1994. [DOI: 10.1016/0040-4039(94)85355-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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45
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46
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47
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48
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