1
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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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2
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Liu D, Zhang Y, Niu D. Preparing glycosyl benzothiazoles from 2-isocyanoaryl thioethers and glycosyl radicals under thermal conditions. Chem Commun (Camb) 2024; 60:5498-5501. [PMID: 38696183 DOI: 10.1039/d4cc00648h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Herein, we report a method for preparing glycosyl benzothiazoles via radical cascade cyclization, in which glycosyl radicals are generated from readily available and bench-stable allyl glycosyl sulfones. This cascade reaction proceeds under simple conditions and tolerates a broad substrate scope in high yield with excellent stereoselectivity. Mechanistic studies support that the reactions proceed via the intermediacy of imidoyl radicals, which attack the appended sulfide unit by a SH2 process to forge the thiazole ring.
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Affiliation(s)
- Daqi Liu
- Department of Emergency, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, and School of Chemical Engineering, Sichuan University, Chengdu 610041, China.
| | - Yang Zhang
- Department of Emergency, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, and School of Chemical Engineering, Sichuan University, Chengdu 610041, China.
| | - Dawen Niu
- Department of Emergency, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, and School of Chemical Engineering, Sichuan University, Chengdu 610041, China.
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3
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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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4
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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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5
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Liu FL, Mei L, Wang LT, Zhou Y, Tang K, Li T, Yi R, Wei WT. Radical bicyclization of 1,6-enynes with sulfonyl hydrazides by the use of TBAI/TBHP in the aqueous phase. Chem Commun (Camb) 2023; 59:6391-6394. [PMID: 37157973 DOI: 10.1039/d3cc01102j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A novel 5-exo-dig/6-endo-trig bicyclization of 1,6-enynes with sulfonyl hydrazides in the aqueous phase using the cheap and available tetrabutylammonium iodide (TBAI)-tert-butyl hydroperoxide (TBHP) combined system is reported. The resulting reaction of diverse nitrogen- and oxygen-polyheterocycles displays high chemical selectivity, high step-economy, and a moderate substrate scope. Moreover, iodosulfonylation can be realized by modulating the structure of the 1,6-enynes.
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Affiliation(s)
- Fa-Liang Liu
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
| | - Lan Mei
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
| | - Ling-Tao Wang
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
| | - Yu Zhou
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
| | - Keqi Tang
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
| | - Ting Li
- College of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang, Henan, 473061, China.
| | - Rongnan Yi
- Criminal Technology Department, Hunan Police Academy, Changsha, Hunan, 410138, China
| | - Wen-Ting Wei
- School of Materials Science and Chemical Engineering, Institute of Mass Spectrometry, Ningbo University, Ningbo, Zhejiang, 315211, China.
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6
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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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7
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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: 6.0] [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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8
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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: 5.5] [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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9
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Zhong W, Xu W, Yang Q, Kato T, Liu Y, Maruoka K. A new approach for the copper-catalyzed functionalization of alkyl hydroperoxides with organosilicon compounds via in-situ-generated alkylsilyl peroxides. Tetrahedron 2022. [DOI: 10.1016/j.tet.2021.132627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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10
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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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11
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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: 3.0] [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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12
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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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13
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Cao Z, Li J, Zhang G. Photo-induced copper-catalyzed sequential 1,n-HAT enabling the formation of cyclobutanols. Nat Commun 2021; 12:6404. [PMID: 34737326 PMCID: PMC8569169 DOI: 10.1038/s41467-021-26670-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 10/08/2021] [Indexed: 11/09/2022] Open
Abstract
Cyclobutanols are privileged cyclic skeletons in natural products and synthetic building blocks. C(sp3)-H functionalization is a prolonged challenge in organic synthesis. The synthesis of cyclobutanols through double C(sp3)-H bond functionalization remains elusive. Here we report the efficient synthesis of cyclobutanols through intermolecular radical [3 + 1] cascade cyclization, involving the functionalization of two C - H bonds through sequential hydrogen atom transfer. The copper complex reduces the iodomethylsilyl alcohols efficiently under blue-light irradiation to initiate the tandem transformation. The mild reaction tolerates a broad range of functional groups and allows for the facile generation of elaborate polycyclic structures.
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Affiliation(s)
- Zhusong Cao
- College of Chemistry, Central China Normal University (CCNU), 152 Luoyu Road, Wuhan, Hubei, 430079, P. R. China.,State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Center for Excellence in Molecular Synthesis, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, P. R. China
| | - Jianye Li
- College of Chemistry, Central China Normal University (CCNU), 152 Luoyu Road, Wuhan, Hubei, 430079, P. R. China
| | - Guozhu Zhang
- College of Chemistry, Central China Normal University (CCNU), 152 Luoyu Road, Wuhan, Hubei, 430079, P. R. China. .,State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Center for Excellence in Molecular Synthesis, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, P. R. China.
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14
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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: 1.3] [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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15
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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: 7.7] [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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