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Frontier AJ, Sinclair PP. Merging Strategy, Improvisation, and Conversation to Solve Problems in Target Synthesis. Acc Chem Res 2021; 54:1817-1829. [PMID: 33705115 DOI: 10.1021/acs.accounts.0c00804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Total synthesis has long been depicted as the quest to conquer the structures created by nature, requiring an unflinching, single-minded devotion to the task. The goal is achieved by chemists with grit, strength of will, and a competitive spirit. While there is some truth to this viewpoint, it does not fully capture the rich experiences gained in this research realm. In our lab, strategic planning, improvisation, and conversation have worked in concert to enable progress. This Account summarizes our efforts to synthesize four different bioactive targets: merrilactone A, rocaglamide, phomactin A, and tetrapetalone A. Certain missteps were integral to success in these synthetic projects. As such, we include the hiccups, and their roles in the evolution of the strategies, along with the results that aligned with our expectations.Two of these projects (merrilactone A and rocaglamide) culminated in the total synthesis of the targets. The challenges presented by merrilactone A spawned a new design strategy for pentannulation using Nazarov cyclization chemistry. This work demonstrated that Lewis acid catalysis is often a viable electrocyclization strategy in activated, polarized pentadienyl cation intermediates. We sought to apply the same logic to the rocaglamide target, but precursors we prepared did not behave according to plan. This situation pushed us to adapt our approach to match the innate reactivity of the substrate, resulting in an on-the-spot improvisation that was not only integral to the success of the project but also expanded our understanding of pentadienyl cation chemistry. In the other two projects (phomactin A and tetrapetalone A), we did not complete a total synthesis but did build the polycyclic core of the target. Even though the hetero [4 + 2] cycloaddition plan for assembling the macrocyclic oxadecalin ring system of phomactin A failed, the original experimental design still enabled us to solve the problem. Through a wholly unanticipated series of events, our focus on the oxadecalin ring system primed us for the discovery of a sequential iodoaldol/oxa-Michael sequence, using the original [4 + 2] building blocks. Then, the bridging ring present in phomactin A demanded we implement this sequence in a transannular fashion. Finally, our successful synthesis of the tetrapetalone core was enabled by consultations with others in the community. Each bond formation seemed to require different expertise, and in three separate instances (C-N cross-coupling, diastereoselective ring-closing metathesis, and oxidative dearomatization) synthetic challenges were overcome through conversation and collaboration.In our experience, the amount of creative power we summon during a target synthesis project correlates directly with the magnitude of the structural challenges we face. When reactivity surprises us, we analyze the problem anew, consult with colleagues, and improvise with the tools at hand. The inevitable misbehavior of a complex system is a strong motivating force, and one that has helped to shape our research program for nearly two decades.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
| | - Paul P. Sinclair
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
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5-Bromoisoxazolidines: synthesis, reactivity and NMR study. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Koenig JJ, Arndt T, Gildemeister N, Neudörfl JM, Breugst M. Iodine-Catalyzed Nazarov Cyclizations. J Org Chem 2019; 84:7587-7605. [DOI: 10.1021/acs.joc.9b01083] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Jonas J. Koenig
- Department of Chemistry, University of Cologne, Greinstraße 4, 50939 Köln, Germany
| | - Thiemo Arndt
- Department of Chemistry, University of Cologne, Greinstraße 4, 50939 Köln, Germany
| | - Nora Gildemeister
- Department of Chemistry, University of Cologne, Greinstraße 4, 50939 Köln, Germany
| | - Jörg-M. Neudörfl
- Department of Chemistry, University of Cologne, Greinstraße 4, 50939 Köln, Germany
| | - Martin Breugst
- Department of Chemistry, University of Cologne, Greinstraße 4, 50939 Köln, Germany
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Zou N, Jiao JW, Feng Y, Pan CX, Liang C, Su GF, Mo DL. Iron(III)/Copper(II)-Cocatalyzed Cycloaddition/[3,3]-Rearrangement/N–O Bond Cleavage To Prepare Polysubstituted Pyrrolizines from N-Vinyl-α,β-Unsaturated Nitrones and Activated Alkynes. Org Lett 2019; 21:481-485. [DOI: 10.1021/acs.orglett.8b03767] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ning Zou
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Ji-Wen Jiao
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Yu Feng
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Cheng-Xue Pan
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Cui Liang
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Gui-Fa Su
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
| | - Dong-Liang Mo
- State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and Technology of China, School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road, Guilin, 541004, China
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Hayashi T, Ohmori K, Suzuki K. Synthetic Study on Carthamin. 2. Stereoselective Approach to C-Glycosyl Quinochalcone via Desymmetrization. Org Lett 2017; 19:866-869. [DOI: 10.1021/acs.orglett.6b03899] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Taiki Hayashi
- Department of Chemistry, Tokyo Institute of Technology, O-okayama,
Meguro-ku, Tokyo 152-8551, Japan
| | - Ken Ohmori
- Department of Chemistry, Tokyo Institute of Technology, O-okayama,
Meguro-ku, Tokyo 152-8551, Japan
| | - Keisuke Suzuki
- Department of Chemistry, Tokyo Institute of Technology, O-okayama,
Meguro-ku, Tokyo 152-8551, Japan
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Carlsen PN, Mann TJ, Hoveyda AH, Frontier AJ. Synthesis of (±)-tetrapetalone A-Me aglycon. Angew Chem Int Ed Engl 2014; 53:9334-8. [PMID: 25045072 PMCID: PMC4260470 DOI: 10.1002/anie.201404410] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Indexed: 11/07/2022]
Abstract
The first synthesis of (±)-tetrapetalone A-Me aglycon is described. Key bond-forming reactions include Nazarov cyclization, a ring-closing metathesis promoted with complete diastereoselectivity by a chiral molybdenum-based complex, tandem conjugate reduction/intramolecular aldol cyclization, and oxidative dearomatization.
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Affiliation(s)
- Peter N. Carlsen
- Department of Chemistry, University of Rochester, Rochester, NY, 14627 (USA)
| | - Tyler J. Mann
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467 (USA)
| | - Amir H. Hoveyda
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467 (USA)
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, NY, 14627 (USA)
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Carlsen PN, Mann TJ, Hoveyda AH, Frontier AJ. Synthesis of (±)-Tetrapetalone A-Me Aglycon. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201404410] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Morgan KM, Ashline DJ, Morgan JP, Greenberg A. Electrospray ionization (ESI) fragmentations and dimethyldioxirane reactivities of three diverse lactams having full, half, and zero resonance energies. J Org Chem 2014; 79:517-28. [PMID: 24313276 PMCID: PMC3959984 DOI: 10.1021/jo402041u] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Three lactams having, respectively, ~20, ~10, and 0 kcal/mol of resonance energy have been subjected to electrospray ionization mass spectrometry (ESI/MS) as well as to attempted reaction with dimethyldioxirane (DMDO). The ESI/MS for all three lactams are consistent with fragmentation from the N-protonated, rather than the O-protonated tautomer. Each exhibits a unique fragmentation pathway. DFT calculations are employed to provide insights concerning these pathways. N-Ethyl-2-pyrrolidinone and 1-azabicyclo[3.3.1]nonan-2-one, the full- and half-resonance lactams, are unreactive with DMDO. The "Kirby lactam" (3,5,7-trimethyl-1-azaadamantan-2-one) has zero resonance energy and reacts rapidly with DMDO to generate a mixture of reaction products. The structure assigned to one of these is the 2,2-dihydroxy-N-oxide, thought to be stabilized by intramolecular hydrogen bonding and buttressing by the methyl substituents. A reasonable pathway to this derivative might involve formation of an extremely labile N-oxide, in a purely formal sense, an example of the hitherto-unknown amide N-oxides, followed by hydration with traces of moisture.
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Affiliation(s)
- Kathleen M. Morgan
- Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125
| | - David J. Ashline
- The Glycomics Center, University of New Hampshire, Durham, NH 03824
| | - Jessica P. Morgan
- Department of Chemistry, University of New Hampshire, Durham, NH 03824
| | - Arthur Greenberg
- Department of Chemistry, University of New Hampshire, Durham, NH 03824
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Mehra V, Kumar V. Single pot diastereoselective synthesis of six membered cyclic (E)-endo-aldonitrones via intramolecular cyclization of ω-alkenyl oximes. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2013.12.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Madabhushi S, Godala KR, Jillella R, Mallu KKR, Chinthala N. A new multicomponent approach to highly functionalized 2,3-dihydroisoxazoles. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2013.11.087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Li P, Teng BT, Jin FG, Li XS, Zhu WD, Xie JW. Synthesis of functionalized 2,3-dihydroisoxazoles by domino reactions in water and unexpected ring-opening reactions of 2,3-dihydroisoxazoles. Org Biomol Chem 2012; 10:244-7. [DOI: 10.1039/c1ob06318a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vaidya T, Manbeck GF, Chen S, Frontier AJ, Eisenberg R. Divergent reaction pathways of a cationic intermediate: rearrangement and cyclization of 2-substituted furyl and benzofuryl enones catalyzed by iridium(III). J Am Chem Soc 2011; 133:3300-3. [PMID: 21322633 DOI: 10.1021/ja111317q] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In contrast to 2-substituted pyrrole enones, furyl and benzofuryl enones do not undergo the Nazarov electrocyclization. Instead, these furyl and benzofuryl enones exhibit unusual rearrangement sequences in the presence of catalytic amounts of [IrBr(CO)(DIM)((R)-(+)-BINAP)](SbF(6))(2) (1; DIM = diethylisopropylidene malonate) and AgSbF(6) (1:1). A 1,2-H shift followed by intramolecular Friedel-Crafts alkylation leads to synthetically valuable cyclohexanones with furanylic quaternary centers. The electrophilicity of 1 is essential for this rearrangement.
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Affiliation(s)
- Tulaza Vaidya
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Yu X, Du B, Wang K, Zhang J. Highly substituted 2,3-dihydroisoxazoles by Et(3)N-catalyzed tandem reaction of electron-deficient 1,3-conjugated enynes with hydroxylamines. Org Lett 2010; 12:1876-9. [PMID: 20334427 DOI: 10.1021/ol100490y] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An Et(3)N-catalyzed tandem reaction of electron-deficient 1,3-conjugated enynes with hydroxylamines was developed which provided rapid, metal-free, and regioselective access to highly substituted multifunctionalized 2,3-dihydroisoxazoles under mild conditions. The reactions of 3-(2-arylethynyl)-4H-chromen-4-ones with hydroxylamines afford beta-amino enones under the same reaction conditions.
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Affiliation(s)
- Xiuzhao Yu
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, PR China
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Canterbury DP, Herrick IR, Um J, Houk KN, Frontier AJ. A Torquoselective Extrusion of Isoxazoline N-Oxides. Application to the Synthesis of Aryl Vinyl and Divinyl Ketones for Nazarov Cyclization. Tetrahedron 2009; 65:3165-3179. [PMID: 20161228 PMCID: PMC2703503 DOI: 10.1016/j.tet.2008.10.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones.
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Affiliation(s)
- Daniel P Canterbury
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
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Attanasi O, Berretta S, De Crescentini L, Favi G, Giorgi G, Mantellini F. Lewis Acid-Catalyzed Synthesis of Functionalized Pyrroles. Adv Synth Catal 2009. [DOI: 10.1002/adsc.200800807] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
A formal synthesis of (+/-)-roseophilin is described. Scandium(III)-catalyzed Nazarov cyclization of 2,5-disubstituted N-tosylpyrrole 19 gives a 5,5'-fused ketopyrrole, and ansa-bridge formation via pi-allyl palladium macrocyclization gives 21.
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Affiliation(s)
- Abdallah Y. Bitar
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
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