1
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Taguchi J, Fukaya S, Fujino H, Inoue M. Total Synthesis of Euphorbialoid A. J Am Chem Soc 2024; 146:34221-34230. [PMID: 39620709 DOI: 10.1021/jacs.4c14520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2024]
Abstract
Euphorbialoid A (1) belongs to the rare diterpenoid family of premyrsinanes and exhibits potent anti-inflammatory effects. The 5/7/6/3-membered carbocycle (ABCD-ring) of 1 contains 11 contiguous stereocenters and seven oxygen-containing functional groups. Moreover, four of the six hydroxy groups of 1 are concentrated in the southern sector and flanked by four structurally different acyl groups. The dense array of various functional groups with disparate reactivities on the tetracyclic ABCD-ring presents a daunting challenge for the chemical synthesis of 1. As a reflection of its formidable complexity, synthesis of 1 or any other premyrsinane diterpenoids has not yet been reported. Here, we devised a novel strategy comprising two stages and achieved the first total synthesis of 1 (35 steps as the longest linear sequence). In the first stage, the ABCD-ring was expeditiously assembled by integrating three powerful transformations: (1) Pt-doped TiO2-catalyzed radical coupling to attach a northern chain to a 6/3-membered CD-ring, (2) Pd-catalyzed decarboxylative asymmetric allylation to construct a quaternary carbon with a southern chain, and (3) a Co-mediated Pauson-Khand reaction to cyclize the two chains into the 5/7-membered AB-ring. In the second stage, three-dimensional structures of the ABCD-ring intermediates were utilized to stereoselectively fabricate the A-ring and site-selectively append the four different acyl groups. In the present total synthesis, we revealed the significance of orchestrating the multistep reaction sequence and incorporating cyclic protective groups. The overall strategy and tactics provide new insights into designing synthetic routes to premyrsinanes and densely oxygenated terpenoids decorated with diverse acyl groups.
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Affiliation(s)
- Junichi Taguchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shintaro Fukaya
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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2
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Gardner KE, de Lescure L, Hardy MA, Tan J, Sigman MS, Paton RS, Sarpong R. Modular synthesis of aryl amines from 3-alkynyl-2-pyrones. Chem Sci 2024; 15:d4sc04885g. [PMID: 39246374 PMCID: PMC11375436 DOI: 10.1039/d4sc04885g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2024] [Accepted: 08/30/2024] [Indexed: 09/10/2024] Open
Abstract
The synthesis of aryl amines from 3-alkynyl-2-pyrones and various amines is described. Mechanistically, the aryl amines are proposed to arise from the 3-alkynyl-2-pyrone substrates through their selective opening in a 1,6-fashion by secondary amines followed by decarboxylation and an unexpected rearrangement. The proposed mechanism is supported by quantum chemical transition-state calculations, which are consistent with the regiochemical outcome. The scope of this transformation spans a variety of 3-alkynyl-2-pyrones and a range of secondary amines. The influence of the secondary amine coupling partners on reaction efficiency was elucidated through data-driven modeling as well as scope exploration. These latter studies revealed that the steric bulk of the secondary amine coupling partner under the reaction conditions serves as a strong indicator of overall reaction efficiency.
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Affiliation(s)
- Kristen E Gardner
- Department of Chemistry, University of California Berkeley CA USA 94708
| | - Louis de Lescure
- Department of Chemistry, Colorado State University Fort Collins CO 80523 USA
| | - Melissa A Hardy
- Department of Chemistry, University of Utah Salt Lake City Utah 84112 USA
| | - Jin Tan
- Department of Chemistry, University of California Berkeley CA USA 94708
| | - Matthew S Sigman
- Department of Chemistry, University of Utah Salt Lake City Utah 84112 USA
| | - Robert S Paton
- Department of Chemistry, Colorado State University Fort Collins CO 80523 USA
| | - Richmond Sarpong
- Department of Chemistry, University of California Berkeley CA USA 94708
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3
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Beleh OM, Alomari S, Weix DJ. Synthesis of Stereodefined Enones from the Cross-Electrophile Coupling of Activated Acrylic Acids with Alkyl Bromides. Org Lett 2024; 26:7217-7221. [PMID: 39162620 PMCID: PMC11516134 DOI: 10.1021/acs.orglett.4c02644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
We report a one-pot synthesis of (E)-trisubstituted enones from acrylic acids through the in situ generation of a 2-pyridyl ester and subsequent cross-electrophile coupling with a nickel catalyst under reducing conditions. The scope of trisubstituted enones is broad and compatible with functionality that can be challenging in established olefination techniques. We highlight conditions necessary to suppress undesired side reactions from the α,β-unsaturated carbonyl and improve cross-electrophile coupling approaches to prepare enones.
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Affiliation(s)
- Omar M. Beleh
- University of Wisconsin–Madison, Madison, WI 53706, USA
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4
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Yamada Y, Yoshinaga R, Matsui Y, Nagatomo M, Fujino H, Inoue M. Et 3Al/Light-Promoted Radical-Polar Crossover Reactions of α-Alkoxyacyl Tellurides. J Org Chem 2024; 89:11701-11706. [PMID: 39110480 DOI: 10.1021/acs.joc.4c01445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Here, we report new radical-polar crossover reactions of α-alkoxy carbon radicals for constructing highly oxygenated molecules with contiguous stereocenters. The method employs a 370 nm UV light-emitting diode (LED) for the photoexcitation of α-alkoxyacyl telluride, and Et3Al as the radical initiator and terminator. First, Et3Al and UV LED promoted radical coupling between the α-alkoxyacyl telluride and cyclopentenone via C-Te bond homolysis, CO expulsion, and C-C bond formation. Second, Et3Al converted the radical species to the corresponding aluminum enolate. Third, the second C-C bond formation occurred via a polar mechanism: intermolecularly with aldehydes/ketones and intramolecularly with epoxide, producing aldol and SN2 adducts, respectively. The present coupling reactions increase the molecular complexity in a single step by stereoselective formation of the two hindered C-C bonds. The devised method is expected to be useful for the expeditious assembly of densely oxygenated natural products.
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Affiliation(s)
- Yutaro Yamada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Risa Yoshinaga
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yuki Matsui
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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5
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Ling B, Yao S, Ouyang S, Bai H, Zhai X, Zhu C, Li W, Xie J. Nickel-Catalyzed Highly Selective Radical C-C Coupling from Carboxylic Acids with Photoredox Catalysis. Angew Chem Int Ed Engl 2024; 63:e202405866. [PMID: 38787803 DOI: 10.1002/anie.202405866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/14/2024] [Accepted: 05/24/2024] [Indexed: 05/26/2024]
Abstract
Controlling the cross-coupling reaction between two different radicals is a long-standing challenge due to the process occurring statistically, which would lead to three products, including two homocoupling products and one cross-coupling product. Generally, the cross-coupling selectivity is achieved by the persistent radical effect (PRE) that requires the presence of a persistent radical and a transient radical, thus resulting in limited radical precursors. In this paper, a highly selective cross-coupling of alkyl radicals with acyl radicals to construct C(sp2)-C(sp3) bonds, or with alkyl radicals to construct C(sp3)-C(sp3) bonds have been achieved with the readily available carboxylic acids and their derivatives (NHPI ester) as coupling partners. The success originates from the use of tridentate ligand (2,2' : 6',2''-terpyridine) to enable radical cross-coupling process to Ni-mediated organometallic mechanism. This protocol offers a facile and flexible access to structurally diverse ketones (up to 90 % yield), and also a new solution for the challenging double decarboxylative C(sp3)-C(sp3) coupling. The broad utility and functional group tolerance are further illustrated by the late-stage functionalization of natural-occurring carboxylic acids and drugs.
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Affiliation(s)
- Bo Ling
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Shunruo Yao
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Shengmao Ouyang
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Haonan Bai
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Xinyi Zhai
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Chengjian Zhu
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Shanghai, 200032, China
- Green Catalysis Center, and College of Chemistry, Zhengzhou University, Zhengzhou, Henan, 450001, China
| | - Weipeng Li
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Jin Xie
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, 211198, China
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6
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Rubel CZ, Ravn AK, Ho HC, Yang S, Li ZQ, Engle KM, Vantourout JC. Stereodivergent, Kinetically Controlled Isomerization of Terminal Alkenes via Nickel Catalysis. Angew Chem Int Ed Engl 2024; 63:e202320081. [PMID: 38494945 DOI: 10.1002/anie.202320081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 03/05/2024] [Accepted: 03/17/2024] [Indexed: 03/19/2024]
Abstract
Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal-catalyzed olefin mono-transposition (i.e., positional isomerization) approaches have emerged to afford valuable E- or Z- internal alkenes from their complementary terminal alkene feedstocks. However, the applicability of these methods has been hampered by lack of generality, commercial availability of precatalysts, and scalability. Here, we report a nickel-catalyzed platform for the stereodivergent E/Z-selective synthesis of internal alkenes at room temperature. Commercial reagents enable this one-carbon transposition of terminal alkenes to valuable E- or Z-internal alkenes via a Ni-H-mediated insertion/elimination mechanism. Though the mechanistic regime is the same in both systems, the underlying pathways that lead to each of the active catalysts are distinct, with the Z-selective catalyst forming from comproportionation of an oxidative addition complex followed by oxidative addition with substrate and the E-selective catalyst forming from protonation of the metal by the trialkylphosphonium salt additive. In each case, ligand sterics and denticity control stereochemistry and prevent over-isomerization.
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Affiliation(s)
- Camille Z Rubel
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICMBS, UMR 5246 du CNRS), Université Lyon, Université Lyon 1, 1 rue Victor Grignard, 69100, Villeurbanne, France
| | - Anne K Ravn
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Hang Chi Ho
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Shenghua Yang
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Zi-Qi Li
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Keary M Engle
- Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Julien C Vantourout
- Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICMBS, UMR 5246 du CNRS), Université Lyon, Université Lyon 1, 1 rue Victor Grignard, 69100, Villeurbanne, France
- Syngenta Crop Protection AG, Schaffauserstrasse, 4332, Stein, Switzerland
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7
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Gan XC, Zhang B, Dao N, Bi C, Pokle M, Kan L, Collins MR, Tyrol CC, Bolduc PN, Nicastri M, Kawamata Y, Baran PS, Shenvi R. Carbon quaternization of redox active esters and olefins by decarboxylative coupling. Science 2024; 384:113-118. [PMID: 38574151 PMCID: PMC11452921 DOI: 10.1126/science.adn5619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 02/28/2024] [Indexed: 04/06/2024]
Abstract
The synthesis of quaternary carbons often requires numerous steps and complex conditions or harsh reagents that act on heavily engineered substrates. This is largely a consequence of conventional polar-bond retrosynthetic disconnections that in turn require multiple functional group interconversions, redox manipulations, and protecting group chemistry. Here, we report a simple catalyst and reductant combination that converts two types of feedstock chemicals, carboxylic acids and olefins, into tetrasubstituted carbons through quaternization of radical intermediates. An iron porphyrin catalyst activates each substrate by electron transfer or hydrogen atom transfer, and then combines the fragments using a bimolecular homolytic substitution (SH2) reaction. This cross-coupling reduces the synthetic burden to procure numerous quaternary carbon---containing products from simple chemical feedstocks.
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Affiliation(s)
- Xu-cheng Gan
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Benxiang Zhang
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Nathan Dao
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Cheng Bi
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Maithili Pokle
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Liyan Kan
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
- College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Michael R. Collins
- Oncology Medicinal Chemistry Department, Pfizer Pharmaceuticals, 10770 Science Center Drive, CA, 92122, United States
| | - Chet C. Tyrol
- Pfizer Medicine Design, 445 Eastern Point Road, Groton, CT, 06340, United States
| | | | | | - Yu Kawamata
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Phil S. Baran
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
| | - Ryan Shenvi
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, CA, 92037, United States
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8
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Kato T, Hagiwara K, Inoue M. Generation and Coupling of Radical Species from α-Alkoxy Bridgehead Carboxylic Acid, Selenide, Telluride, Acyl Selenide, and Acyl Telluride. Chem Pharm Bull (Tokyo) 2024; 72:767-771. [PMID: 39198181 DOI: 10.1248/cpb.c24-00441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2024]
Abstract
α-Alkoxy bridgehead radicals enable intermolecular construction of sterically congested C-C bonds due to their sterically accessible nature. We implemented these radical species into total syntheses of various densely oxygenated natural products and demonstrated their exceptional versatility. Herein, we employed different precursors to generate the same α-alkoxy bridgehead radical and compared the efficacy of the precursors for coupling reactions. Specifically, the bridgehead radical of the trioxaadamantane structure was formed from α-alkoxy carboxylic acid, selenide/telluride, and acyl selenide/acyl telluride, and reacted with 4-((tert-butyldimethylsilyl)oxy)cyclopent-2-en-1-one and 5-oxo-1-cyclopentene-1-carbonitrile. The efficiency of the bridgehead radical formation and subsequent coupling reaction significantly depended on the structures of the precursors and acceptors as well as the reaction conditions. Our findings provide new insights for selecting the appropriate substrates of key coupling reactions in the total synthesis of complex natural products.
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Affiliation(s)
- Takehiro Kato
- Graduate School of Pharmaceutical Sciences, The University of Tokyo
| | - Koichi Hagiwara
- Graduate School of Pharmaceutical Sciences, The University of Tokyo
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo
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9
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Watanabe Y, Sakata K, Urabe D, Hagiwara K, Inoue M. Formal Total Synthesis of Batrachotoxin Enabled by Radical and Weix Coupling Reactions. J Org Chem 2023. [PMID: 38051654 DOI: 10.1021/acs.joc.3c02290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Batrachotoxin (1), originally isolated from a Columbian poison-dart frog, is a steroidal alkaloid. Its 6/6/6/5-membered carbocycle (ABCD-ring) contains two double bonds, one nitrogen, and five oxygen functionalities. We developed a radical-based convergent strategy and realized the total synthesis of 1 in 28 steps. The AB-ring and D-ring fragments were efficiently synthesized and linked by exploiting a powerful Et3B/O2-mediated radical coupling reaction. Vinyl triflate and vinyl bromide were then utilized for a Pd/Ni-promoted Weix coupling reaction to cyclize the C-ring. A hydroxy group of the C-ring was stereoselectively installed by a decarboxylative hydroxylation reaction to prepare an advanced intermediate of our previous total synthesis of 1.
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Affiliation(s)
- Yuuki Watanabe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Komei Sakata
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Daisuke Urabe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Koichi Hagiwara
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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10
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Watanabe T, Oga K, Matoba H, Nagatomo M, Inoue M. Total Synthesis of Taxol Enabled by Intermolecular Radical Coupling and Pd-Catalyzed Cyclization. J Am Chem Soc 2023; 145:25894-25902. [PMID: 37972241 DOI: 10.1021/jacs.3c10658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Taxol (1) is a clinically used antineoplastic diterpenoid. The tetracyclic ring system comprises a 6/8/6-membered carbocycle (ABC-ring) and a fused oxetane ring (D-ring) embedded with a bridgehead double bond and decorated with multiple oxygen functionalities. Here, we report a convergent total synthesis of this exceedingly complex natural product. The C-ring fragment was designed to possess a bromocyclohexenone and an extra tetrahydrofuran ring to control the reactivity and selectivity, as well as to minimize functional group manipulations en route to 1. The α-alkoxyacyl telluride of the A-ring served as a radical precursor, and intermolecular radical coupling with the C-ring realized the installation of the C2- and C3-stereocenters and reductive removal of the bromide. After the C8-quaternary stereocenter was constructed by exploiting the three-dimensional shape of the intermediate, the C11-vinyl triflate of A-ring and the C8-methyl ketone of C-ring were utilized for Pd(0)-catalyzed cyclization of the central eight-membered B-ring with the bridgehead olefin. Adjustment of the oxidation level and attachment of the oxetane D-ring completed the total synthesis of 1 (28 steps, as the longest linear sequence). The fragment design principle and implementation of the powerful radical coupling reaction described in the present synthesis provide valuable information for planning and executing syntheses of diverse densely oxygenated terpenoids.
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Affiliation(s)
- Takahiro Watanabe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Kyohei Oga
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Hiroaki Matoba
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
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11
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Frischling MC, Herzon SB. On the Abundance and Stability of Diazo-Containing Secondary Metabolites: Enantioselective Synthesis of (-)-Nenestatin A. Org Lett 2023; 25:3723-3727. [PMID: 37172275 PMCID: PMC10468809 DOI: 10.1021/acs.orglett.3c01175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Here, we report an enantioselective synthesis of the monomeric nes product (-)-nenestatin A, via the intermediary diazofluorene "diazonenestatin A." Our route features a convergent, aldol-based fragment coupling to assemble the carbon skeleton and a diazotransfer to a highly conjugated tetracyclic fulvene. We find that diazonenestatin A is transformed to nenestatin A under conditions that mimic the bacterial fermentation, suggesting that the nes pathway may produce unstable diazofluorene products that have eluded isolation.
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Affiliation(s)
- Madeline C Frischling
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- Departments of Pharmacology and Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut 06520, United States
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12
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Imamura Y, Takaoka K, Komori Y, Nagatomo M, Inoue M. Total Synthesis of Taxol Enabled by Inter- and Intramolecular Radical Coupling Reactions. Angew Chem Int Ed Engl 2023; 62:e202219114. [PMID: 36646637 DOI: 10.1002/anie.202219114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/18/2023]
Abstract
Taxol is a clinically used drug for the treatment of various types of cancers. Its 6/8/6/4-membered ring (ABCD-ring) system is substituted by eight oxygen functional groups and flanked by four acyl groups, including a β-amino acid side chain. Here we report a 34-step total synthesis of this unusually oxygenated and intricately fused structure. Inter- and intramolecular radical coupling reactions connected the A- and C-ring fragments and cyclized the B-ring, respectively. Functional groups of the A- and C-rings were then efficiently decorated by employing newly developed chemo-, regio-, and stereoselective reactions. Finally, construction of the D-ring and conjugation with the β-amino acid delivered taxol. The powerful coupling reactions and functional group manipulations implemented in the present synthesis provide new valuable information for designing multistep target-oriented syntheses of diverse bioactive natural products.
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Affiliation(s)
- Yusuke Imamura
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kyohei Takaoka
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yuma Komori
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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13
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Hsu IT, Herzon SB. Fragment Coupling Approach to Diaporthein B. J Org Chem 2023; 88:2221-2244. [PMID: 36737056 DOI: 10.1021/acs.joc.2c02655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Pimarane diterpenes are produced by a diverse array of plants, fungi, and bacteria. Many members of this family possess antimicrobial and antiproliferative activities. The pimarane diterpenes are characterized by a tricyclic carbon scaffold comprising three fused six-membered rings and at least three quaternary centers. Here, we describe two convergent, fragment-based strategies toward the synthesis of diaporthein B (3), one of the most highly oxidized pimarane diterpenes. The first approach provided access to the tricyclic carbon scaffold of the target and featured a highly diastereoselective fragment coupling, a novel carbonylative Stille cross-coupling to directly access an α-hydroxyketone from a vinyl iodide, and a tandem aldol cyclization-deprotection cascade. The second route utilized a diastereoselective 1,4-addition of a silyloxyfuran to an unsaturated ketone, followed by an epoxidation-ring opening sequence, to access a highly oxidized intermediate containing two elaborated cyclohexane rings. The chemistry developed herein may ultimately be useful in an eventual synthesis of this class of natural products.
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Affiliation(s)
- Ian Tingyung Hsu
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States.,Departments of Pharmacology and Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut06520, United States
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14
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Shimakawa T, Nakamura S, Asai H, Hagiwara K, Inoue M. Total Synthesis of Puberuline C. J Am Chem Soc 2023; 145:600-609. [PMID: 36538394 DOI: 10.1021/jacs.2c11259] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Puberuline C (1) is an architecturally complex C19-diterpenoid alkaloid with a unique ring fusion pattern. The 6/7/5/6/6/6-membered rings (ABCDEF-rings) contain one tertiary amine and six oxygen functionalities, and possess 12 contiguously aligned stereocenters, three of which are quaternary. These structural features of 1 make its chemical construction exceptionally challenging. Here, we disclose the first total synthesis of 1. The synthesis was accomplished from 2-cyclohexenone (9) by integrating radical cascade and Mukaiyama aldol reactions as the key transformations. A double Mannich reaction fused the A- and E-rings, and Sonogashira coupling attached the C-ring, efficiently leading to ACE-rings with the requisite 19 carbons of 1. The chemically stable tertiary chloride of the ACE-ring structure was then transformed to the corresponding bridgehead radical, which participated in the simultaneous cyclization of the B- and F-rings via a highly organized radical cascade process. This unusual step installed five contiguous stereocenters, including two quaternary carbons, without damaging the preexisting multiple polar functionalities. Subsequently, the intramolecular Mukaiyama aldol reaction between silyl enol ether and acetal was realized by applying a combination of SnCl4 and ZnCl2, forging the last remaining D-ring of the hexacycle. Finally, 3 was elaborated into 1 through regio- and stereoselective functionalizations of the BCD-rings. Our novel radical-based strategy achieved the total synthesis of 1 in 32 total steps from simple 9, demonstrating the power of the radical cascade reaction to streamline the assembly of highly complex molecules.
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Affiliation(s)
- Tsukasa Shimakawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Shu Nakamura
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Hibiki Asai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Koichi Hagiwara
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo113-0033, Japan
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15
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Wang L, Chen Z, Fan G, Liu X, Liu P. Organophotoredox and Hydrogen Atom Transfer Cocatalyzed C-H Alkylation of Quinoxalin-2(1 H)-ones with Aldehydes, Amides, Alcohols, Ethers, or Cycloalkanes. J Org Chem 2022; 87:14580-14587. [PMID: 36206555 DOI: 10.1021/acs.joc.2c01967] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Described is a mild method that merges organophotoredox catalysis with hydrogen atom transfer to enable C-H alkylation of quinoxalin-2(1H)-ones with feedstock aldehydes, amides, alcohols, ethers, or cycloalkanes. This reaction occurred under environmentally benign and external oxidant-free reaction conditions, providing a general and sustainable access to various C3-alkylated quinoxalinone derivatives with broad substituent diversity and good functional group compatibility.
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Affiliation(s)
- Liling Wang
- Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, Generic Drug Research Center of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi 563000, China
| | - Zhaoxing Chen
- Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, Generic Drug Research Center of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi 563000, China
| | - Guohua Fan
- Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, Generic Drug Research Center of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi 563000, China
| | - Xiaozu Liu
- Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, Generic Drug Research Center of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi 563000, China.,Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563000, China
| | - Peijun Liu
- Key Laboratory of Biocatalysis & Chiral Drug Synthesis of Guizhou Province, Generic Drug Research Center of Guizhou Province, School of Pharmacy, Zunyi Medical University, Zunyi 563000, China.,Key Laboratory of Basic Pharmacology of Ministry of Education and Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563000, China
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16
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Xu Z, DiBello M, Wang Z, Rose JA, Chen L, Li X, Herzon SB. Stereocontrolled Synthesis of the Fully Glycosylated Monomeric Unit of Lomaiviticin A. J Am Chem Soc 2022; 144:16199-16205. [PMID: 35998350 DOI: 10.1021/jacs.2c07631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We describe a stereocontrolled synthesis of 3, the fully glycosylated monomeric unit of the dimeric cytotoxic bacterial metabolite (-)-lomaiviticin A (2). A novel strategy involving convergent, site- and stereoselective coupling of the β,γ-unsaturated ketone 6 and the naphthyl bromide 7 (92%, 15:1 diastereomeric ratio (dr)), followed by radical-based annulation and silyl ether cleavage, provided the tetracycle 5 (57% overall), which contains the carbon skeleton of the aglycon of 3. The β-linked 2,4,6-trideoxy-4-aminoglycoside l-pyrrolosamine was installed in 73% yield and with 15:1 β:α selectivity using a modified Koenigs-Knorr glycosylation. The diazo substituent was introduced via direct diazo transfer to an electron-rich benzoindene (4 → 27). The α-linked 2,6-dideoxyglycoside l-oleandrose was introduced by gold-catalyzed activation of an o-alkynyl glycosylbenzoate (75%, >20:1 α:β selectivity). A carefully orchestrated endgame sequence then provided efficient access to 3. Cell viability studies indicated that monomer 3 is not cytotoxic at concentrations up to 1 μM, providing conclusive evidence that the dimeric structure of (-)-lomaiviticin A (2) is required for cytotoxic effects. The preparation of 3 provides a foundation to complete the synthesis of (-)-lomaiviticin A (2) itself.
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Affiliation(s)
- Zhi Xu
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Mikaela DiBello
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Zechun Wang
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - John A Rose
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Lei Chen
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Xin Li
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut06520, United States.,Departments of Pharmacology and Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut06520, United States
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17
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Yang F, Porco JA. Unified, Asymmetric Total Synthesis of the Asnovolins and Related Spiromeroterpenoids: A Fragment Coupling Approach. J Am Chem Soc 2022; 144:12970-12978. [DOI: 10.1021/jacs.2c05366] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Feng Yang
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - John A. Porco
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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18
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Suga T, Takada R, Shimazu S, Sakata M, Ukaji Y. Highly ( E)-Selective Trisubstituted Alkene Synthesis by Low-Valent Titanium-Mediated Homolytic Cleavage of Alcohol C-O Bond. J Org Chem 2022; 87:7487-7493. [PMID: 35609287 DOI: 10.1021/acs.joc.2c00246] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ti-mediated homolytic C-O bond cleavage was useful for cascade radical-ionic reactions. Benzyl alcohols treated with TiCl4(col) (col = 2,4,6-collidine) and Mn powder generated the corresponding benzyl radicals; in addition, their reaction with 2-carboxyallyl acetates and the subsequent elimination of the acetoxy group yielded α,β-unsaturated carbonyl compounds with exclusive (E)-stereoselectivity. The simplicity of the procedure and its wide substrate scope represent a solution to the drawbacks associated with the reactions.
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Affiliation(s)
- Takuya Suga
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Ryusei Takada
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Shoma Shimazu
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Mizuki Sakata
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
| | - Yutaka Ukaji
- Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan
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19
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Chakrabarty A, Mukherjee S. Iridium-Catalyzed Enantioselective and Chemodivergent Allenylic Alkylation of Vinyl Azides for the Synthesis of α-Allenylic Amides and Ketones. Angew Chem Int Ed Engl 2022; 61:e202115821. [PMID: 35044711 DOI: 10.1002/anie.202115821] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Indexed: 01/14/2023]
Abstract
The first enantioselective synthesis of α-allenylic amides and ketones through allenylic alkylation of vinyl azides is reported. In these chemodivergent reactions, cooperatively catalyzed by a IrI /(phosphoramidite,olefin) complex and Sc(OTf)3 , vinyl azides act as the surrogate for both amide enolates and ketone enolates. The desiccant (molecular sieves) plays a crucial role in controlling the chemodivergency of this enantioconvergent and regioselective reaction: Under otherwise identical reaction conditions, the presence of the desiccant led to α-allenylic amides, while its absence resulted in α-allenylic ketones. Utilizing racemic allenylic alcohols as the alkylating agent, the overall process represents a dynamic kinetic asymmetric transformation (DyKAT), where both the products are formed with the same absolute configuration. To the best of our knowledge, this is the first example of the use of vinyl azide as the ketone enolate surrogate in an enantioselective transformation.
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Affiliation(s)
- Aditya Chakrabarty
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560 012, India
| | - Santanu Mukherjee
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560 012, India
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20
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Chakrabarty A, Mukherjee S. Iridium‐Catalyzed Enantioselective and Chemodivergent Allenylic Alkylation of Vinyl Azides for the Synthesis of α‐Allenylic Amides and Ketones**. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202115821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Aditya Chakrabarty
- Department of Organic Chemistry Indian Institute of Science Bangalore 560 012 India
| | - Santanu Mukherjee
- Department of Organic Chemistry Indian Institute of Science Bangalore 560 012 India
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21
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Hikone Y, Kato T, Nagatomo M, Inoue M. Total Synthesis of Resiniferatoxin Enabled by Photocatalytic Decarboxylative Radical Cyclization. Org Lett 2022; 24:929-933. [PMID: 35043639 DOI: 10.1021/acs.orglett.1c04286] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Resiniferatoxin (1) is a complex daphnane diterpenoid with a highly oxygenated 5/7/6-membered ABC-ring system. Here we report a new synthetic route to 1 that requires 27 steps from a starting d-ribose derivative. The carbon spacer and A-ring are sequentially attached to the C-ring by radical allylation and Stille coupling reactions, respectively. An Ir(III)-catalyzed photoinduced decarboxylative radical reaction then forged the sterically hindered bond between the tetra- and trisubstituted carbons to cyclize the central seven-membered B-ring.
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Affiliation(s)
- Yuto Hikone
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takehiro Kato
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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22
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Yu XC, Zhang CC, Wang LT, Li JZ, Li T, Wei WT. The synthesis of seven- and eight-membered rings by radical strategies. Org Chem Front 2022. [DOI: 10.1039/d2qo00774f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radical strategies for preparation of seven- or eight-membered rings.
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Affiliation(s)
- Xuan-Chi Yu
- Institute of Drug Discovery Technology, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Can-Can Zhang
- Institute of Drug Discovery Technology, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Ling-Tao Wang
- Institute of Drug Discovery Technology, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Jiao-Zhe Li
- Institute of Drug Discovery Technology, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China
| | - Ting Li
- College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang, Henan, 473061, China
| | - Wen-Ting Wei
- Institute of Drug Discovery Technology, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China
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23
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Kuwana D, Komori Y, Nagatomo M, Inoue M. Photoinduced Decarboxylative Radical Coupling Reaction of Multiply Oxygenated Structures by Catalysis of Pt-Doped TiO 2. J Org Chem 2021; 87:730-736. [PMID: 34936365 DOI: 10.1021/acs.joc.1c02736] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new reaction system was devised for decarboxylative radical coupling reactions by heterogeneous semiconductor photoredox catalysis. When an α-alkoxy carboxylic acid and Pt-doped TiO2 in EtOAc were irradiated with a violet light-emitting diode at room temperature, the photogenerated electron hole of TiO2 oxidatively induced the ejection of CO2 via the formation of a carboxyl radical to produce the corresponding α-alkoxy radical. C(sp3)-C(sp3) bond formation between the radicals led to dimers with reductive conversion of protons to H2 by the photogenerated electron. Alternatively, in the presence of an electron-deficient olefin, an intermolecular radical addition reaction occurred, resulting in the formation of a 1,4-adduct via single-electron reduction and subsequent protonation. These operationally simple and mild transformations are amenable to the one-step assembly of densely oxygenated linear and branched carbon chains.
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Affiliation(s)
- Daiki Kuwana
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yuma Komori
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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24
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Fujino H, Nagatomo M, Inoue M. Total Syntheses of Hikosamine and Hikizimycin. J Org Chem 2021; 86:16220-16230. [PMID: 34569228 DOI: 10.1021/acs.joc.1c01773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hikizimycin (1) is a potent anthelmintic and antibacterial natural product. The core 4-amino-4-deoxyundecose sugar (hikosamine) of 1 consists of an 11-carbon linear chain substituted with one amino group and 10 hydroxy groups. The C1 and C6O positions of the 10 contiguous stereocenters are further appended by a cytosine base and a 3-amino-3-deoxyglucose sugar (kanosamine), respectively. Since the structural determination in the early 1970s, synthetic chemists have been attracted by this exceedingly complex structure and have investigated the full chemical construction of 1. These synthetic efforts culminated in four syntheses of the protected hikosamines and two total syntheses of 1. In this Perspective, we summarize the strategies and tactics utilized in these syntheses to showcase the evolution of modern natural product synthesis.
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Affiliation(s)
- Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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25
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Nay B. Total Synthesis of Poisonous Aconitum Alkaloids Empowered by a Fragment Coupling Strategy. ACS CENTRAL SCIENCE 2021; 7:1298-1299. [PMID: 34471674 PMCID: PMC8393206 DOI: 10.1021/acscentsci.1c00887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Affiliation(s)
- Bastien Nay
- Laboratoire de Synthèse Organique, Ecole Polytechnique, CNRS, ENSTA,
Institut Polytechnique de Paris, Palaiseau 91128, France
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26
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Ju W, Wang X, Tian H, Gui J. Asymmetric Total Synthesis of Clionastatins A and B. J Am Chem Soc 2021; 143:13016-13021. [PMID: 34398601 DOI: 10.1021/jacs.1c07511] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Herein we report the first total synthesis of polychlorinated steroids clionastatins A and B, which was accomplished asymmetrically by means of a convergent, radical fragment coupling approach. Key features of the synthesis include an Ireland-Claisen rearrangement to introduce the C5 stereocenter (which was ultimately transferred to the C10 quaternary stereocenter of the clionastatins via a traceless stereochemical relay), a regioselective acyl radical conjugate addition to join the two fragments, an intramolecular Heck reaction to install the C10 quaternary stereocenter, and a diastereoselective olefin dichlorination to establish the synthetically challenging pseudoequatorial dichlorides. This work also enabled us to determine that the true structures of clionastatins A and B are in fact C14 epimers of the originally proposed structures.
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Affiliation(s)
- Wei Ju
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Xudong Wang
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Hailong Tian
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Jinghan Gui
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
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27
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Hirose A, Watanabe A, Ogino K, Nagatomo M, Inoue M. Unified Total Syntheses of Rhamnofolane, Tigliane, and Daphnane Diterpenoids. J Am Chem Soc 2021; 143:12387-12396. [PMID: 34319739 DOI: 10.1021/jacs.1c06450] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Rhamnofolane, tigliane, and daphnane diterpenoids are structurally complex natural products with multiple oxygen functionalities, making them synthetically challenging. While these diterpenoids share a 5/7/6-trans-fused ring system (ABC-ring), the three-carbon substitutions at the C13- and C14-positions on the C-ring and appending oxygen functional groups differ among them, accounting for the disparate biological activities of these natural products. Here, we developed a new, unified strategy for expeditious total syntheses of five representative members of these three families, crotophorbolone (1), langduin A (2), prostratin (3), resiniferatoxin (4), and tinyatoxin (5). Retrosynthetically, 1-5 were simplified into their common ABC-ring 6 by detaching the three-carbon units and the oxygen-appended groups. Intermediate 6 with six stereocenters was assembled from four achiral fragments in 12 steps by integrating three powerful transformations, as follows: (i) asymmetric Diels-Alder reaction to induce formation of the C-ring; (ii) π-allyl Stille coupling reaction to set the trisubstituted E-olefin of the B-ring; and (iii) Eu(fod)3-promoted 7-endo cyclization of the B-ring via the generation of a bridgehead radical. Then 6 was diversified into 1-5 by selective installation of the different functional groups. Attachment of the C14-β-isopropenyl and isopropyl groups led to 1 and 2, respectively, while oxidative acetoxylation and C13,14-β-dimethylcyclopropane formation gave rise to 3. Finally, formation of an α-oriented caged orthoester by C13-stereochemical inversion and esterification with two different homovanillic acids delivered 4 and 5 with a C13-β-isopropenyl group. This unified synthetic route to 1-5 required only 16-20 total steps, demonstrating the exceptional efficiency of the present strategy.
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Affiliation(s)
- Akira Hirose
- Graduate School of Pharmaceutical Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ayumu Watanabe
- Graduate School of Pharmaceutical Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kohei Ogino
- Graduate School of Pharmaceutical Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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28
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Nagatomo M, Inoue M. Convergent Assembly of Highly Oxygenated Natural Products Enabled by Intermolecular Radical Reactions. Acc Chem Res 2021; 54:595-604. [PMID: 33406830 DOI: 10.1021/acs.accounts.0c00792] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Natural products with a high ratio of sp3-hybridized atoms and oxygen-substituted stereogenic centers represent privileged structures for the development of pharmaceuticals and chemical probes. The multiple oxygen functionalities of these natural products endow their potent and selective biological activities, although they significantly heighten the challenge of their chemical assemblies. We focused on developing efficient strategies for the total syntheses of this biologically and chemically important class of molecules. A convergent strategy is more advantageous than a linear strategy for designing a shorter synthetic route because a convergent strategy enables direct coupling of functionalized fragments whereas a linear strategy involves stepwise construction of a molecule from its terminus. Radical reactions are preferred over polar reactions for the coupling of heavily functionalized and sp3-rich fragments, as they allow for C(sp3)-C(sp3) coupling without damaging diverse polar functional groups. With these considerations in mind, we designed radical-based convergent strategies for assembling highly oxygenated natural products. Here we summarize the concise total syntheses of asimicin (1, antibiotic activity), 1-hydroxytaxinine (2, cytotoxicity), polyoxins (3, antifungal activity), and hikizimycin (4, anthelmintic activity) as representative examples. Retrosynthetic disconnection at the central part of these molecules produces highly substituted α-alkoxy radicals as synthons. In the synthetic direction, the α-alkoxy radicals were generated from the corresponding α-alkoxyacyl tellurides in a unified fashion, and then utilized for four distinct coupling reactions. Formation of the Et radical from Et3B and O2 homolytically cleaves the C-Te bond of α-alkoxyacyl telluride, and the facile expulsion of carbon monoxide from the acyl radical leads to the α-alkoxy radical. Dimerization of the stabilized α-alkoxy radical resulted in the core structure of 1 with 10 contiguous stereocenters. The coupling adduct was derivatized to 1 through the attachment of two different carbon chains (17 steps as the longest linear sequence). Alternatively, intermolecular addition reactions of the α-alkoxy radicals to electron-deficient C═C, C═N, and C═O bonds, followed by Et3B-mediated radical termination, led to the core structures of 2, 3, and 4, respectively. Intermolecular coupling between the α-alkoxy radical and the cyclohexenone derivative and intramolecular pinacol coupling gave rise to the 6/8/6-fused ring system of 2, which was transformed to 2 (26 steps). The two amino acid moieties of 3 were prepared by combining the α-alkoxy radical and the oxime and were then condensed to complete the synthesis of 3 (11 steps). Furthermore, a combination of α-alkoxyacyl telluride and Et3B/O2 realized a novel addition reaction of α-alkoxy radicals to aldehydes. This method was incorporated in the construction of the core 4-amino-5-deoxyundecose with 10 contiguous stereocenters, which was fabricated with two appendage structures to deliver 4. The four total syntheses described here demonstrate the versatility and robustness of intermolecular radical reactions. These syntheses will also provide new insights for retrosynthetic analyses in the field of organic chemistry and streamline synthetic routes to various bioactive natural products with multiple oxygen functionalities.
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Affiliation(s)
- Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Fukuda T, Nagatomo M, Inoue M. Total Synthesis of Diospyrodin and Its Three Diastereomers. Org Lett 2020; 22:6468-6472. [PMID: 32806173 DOI: 10.1021/acs.orglett.0c02280] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Antibacterial diospyrodin (1) was synthesized in 13 steps. Et3B and O2 promoted the formation of an α-alkoxy carbon radical from l-ribose-derived α-alkoxyacyl telluride 5, which reacted with d-glucose-derived aldehyde 4. The radical addition realized the convergent assembly of the contiguously hydroxylated carbon-chain of 3-α and greatly contributed to streamlining the synthetic route. Compound 3-α was transformed not only to 1 but also to its three diastereomers by functional group manipulations.
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Affiliation(s)
- Takumi Fukuda
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Tomanik M, Herzon SB. Synthesis of (–)-Myrocin G via a Cascade Coupling. TRENDS IN CHEMISTRY 2020. [DOI: 10.1016/j.trechm.2020.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Fujino H, Fukuda T, Nagatomo M, Inoue M. Convergent Total Synthesis of Hikizimycin Enabled by Intermolecular Radical Addition to Aldehyde. J Am Chem Soc 2020; 142:13227-13234. [PMID: 32628018 DOI: 10.1021/jacs.0c06354] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hikizimycin (1), which exhibits powerful anthelmintic activity, has the most densely functionalized structure among nucleoside antibiotics. A central 4-amino-4-deoxyundecose of 1 possesses 10 contiguous stereocenters on a C1-C11 linear chain and is decorated with a cytosine base at C1 and a 3-amino-3-deoxyglucose at C6-OH. These distinctive structural features of 1 make it an extremely challenging target for de novo construction. Herein, we report a convergent total synthesis of 1 from four known components: 3-azide-3-deoxyglucose derivative 4, bis-TMS-cytosine 5, d-mannose 9, and d-galactose derivative 10. We first designed and devised a novel radical coupling reaction between multiply hydroxylated aldehydes and α-alkoxyacyl tellurides. The generality and efficiency of this process was demonstrated by the coupling of 7c and 8, which were readily accessible from two hexoses, 9 and 10, respectively. Et3B and O2 rapidly induced decarbonylative radical formation from α-alkoxyacyl telluride 8, and intermolecular addition of the generated α-alkoxy radical to aldehyde 7c yielded 4-amino-4-deoxyundecose 6-α with installation of the desired C5,6-stereocenters. Subsequent attachments of the cytosine with 5 and of the 3-azide-3-deoxyglucose with 4 were realized through selective activation of the C1-acetal and selective deprotection of the C6-hydroxy group. Finally, the 3 amino and 10 hydroxy groups were liberated in a single step to deliver the target 1. Thus, the combination of the newly developed radical-coupling and protective-group strategies minimized the functional group manipulations and thereby enabled the synthesis of 1 from 10 in only 17 steps. The present total synthesis demonstrates the versatility of intermolecular radical addition to aldehyde for the first time and offers a new strategic design for multistep target-oriented syntheses of various nucleoside antibiotics and other bioactive natural products.
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Affiliation(s)
- Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Takumi Fukuda
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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Tomanik M, Economou C, Frischling MC, Xue M, Marks VA, Mercado BQ, Herzon SB. Development of a Convergent Enantioselective Synthetic Route to (-)-Myrocin G. J Org Chem 2020; 85:8952-8989. [PMID: 32615040 DOI: 10.1021/acs.joc.0c00891] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Myrocins are a family of antiproliferative antibiotic fungal metabolites possessing a masked electrophilic cyclopropane. Preliminary chemical reactivity studies imputed the bioactivity of these natural products to a DNA cross-linking mechanism, but this hypothesis was not confirmed by studies with native DNA. We recently reported a total synthesis of (-)-myrocin G (4), the putative active form of the metabolite myrocin C (1), that featured a carefully orchestrated tandem fragment coupling-annulation cascade. Herein, we describe the evolution of our synthetic strategy toward 4 and report the series of discoveries that prompted the design of this cascade coupling. Efforts to convert the diosphenol (-)-myrocin G (4) to the corresponding 5-hydroxy-γ-lactone isomer myrocin C (1) are also detailed. We present a preliminary evaluation of the antiproliferative activities of (-)-myrocin G (4) and related structures, as well as DNA cross-linking studies. These studies indicate that myrocins do not cross-link DNA, suggesting an alternative mode of action potentially involving a protein target.
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Affiliation(s)
- Martin Tomanik
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Christos Economou
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Madeline C Frischling
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Mengzhao Xue
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Victoria A Marks
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, United States
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