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Kaneko M, Yamashita A, Yasuno Y, Yamauchi K, Sakai K, Oishi T. Synthesis of the MN Ring of Caribbean Ciguatoxin C-CTX-1 via Desymmetrization by Acetal Formation. Org Lett 2024; 26:855-859. [PMID: 38241474 DOI: 10.1021/acs.orglett.3c04013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2024]
Abstract
The MN ring of Caribbean ciguatoxin C-CTX-1 was synthesized from a meso-syn-2,7-dimethyloxepane derivative corresponding to the M ring via desymmetrization by acetal formation with a camphor derivative, followed by construction of the N ring via the Horner-Wadsworth-Emmons reaction and acetal formation. The meso-syn-2,7-dimethyloxepane derivative was synthesized via photoinduced electrocyclization of a conjugated exo-diene under flow conditions, giving a cyclobutene derivative, followed by ring expansion via oxidative cleavage and diastereoselective reduction of a β-hydroxy ketone.
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Affiliation(s)
- Masahiro Kaneko
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Atsuhiro Yamashita
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Yoko Yasuno
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kosei Yamauchi
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Ken Sakai
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Tohru Oishi
- Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Moooka, Nishi-ku, Fukuoka 819-0395, Japan
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Sasaki M, Iwasaki K, Arai K, Hamada N, Umehara A. Convergent Synthesis of the HIJKLMN-Ring Fragment of Caribbean Ciguatoxin C-CTX-1 by a Late-Stage Reductive Olefin Coupling Approach. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2022. [DOI: 10.1246/bcsj.20220070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577
| | - Kotaro Iwasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577
| | - Keisuke Arai
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577
| | - Naoya Hamada
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577
| | - Atsushi Umehara
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577
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Sakai T, Mizuno S, Sone A, Hori Y, Yamazaki W, Takazawa K, Mori Y. Biomimetic Construction of a syn-2,7-Dimethyloxepane Ring via 7- Endo Cyclization. J Org Chem 2021; 87:579-594. [PMID: 34958571 DOI: 10.1021/acs.joc.1c02600] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
syn-2,7-Dimethyloxepane is a unique structure observed in natural ladder-shaped polycyclic ethers (LSPs), such as Caribbean ciguatoxins, gymnocin-B, and brevisulcenal-F that exhibit potent biological activities. Thus, the successful construction of this seven-membered ring is desirable, but its ring strain and the 1,3-repulsion between its two methyl groups makes this process difficult. Herein, we prepared syn-2,7-dimethyloxepanes via 7-endo cyclizations of vinyl epoxides that break Baldwin's rules. Such a biomimetic approach to syn-2,7-dimethyloxepanes has not yet been reported; however, we achieved this challenging cyclization with the aid of a cis-olefin tether and an unsubstituted vinyl group. The NO-ring fragment of gymnocin-B was also prepared from one of these 7-endo cyclized products, demonstrating the potential application of this strategy in constructing bioactive LSPs.
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Affiliation(s)
- Takeo Sakai
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Sae Mizuno
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Akitaka Sone
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Yasuko Hori
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Wakana Yamazaki
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Keisuke Takazawa
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
| | - Yuji Mori
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan
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Sasaki M, Iwasaki K, Arai K. Synthesis and Structural Implication of the JKLMN-Ring Fragment of Caribbean Ciguatoxin C-CTX-1. J Org Chem 2021; 86:4580-4597. [PMID: 33667088 DOI: 10.1021/acs.joc.0c03031] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synthesis of the JKLMN-ring fragment of Caribbean ciguatoxin C-CTX-1, the causative toxin of ciguatera fish poisoning in the Caribbean Sea and the Northeast Atlantic areas, is described in detail. Key to the synthesis are a [2,3]-sigmatropic rearrangement to construct a seven-membered α-hydroxy exo-enol ether, stereoselective construction of an angular tetrasubstituted stereogenic center on the seven-membered M-ring by a hydrogen atom transfer-based reductive olefin coupling, Suzuki-Miyaura coupling of the KLMN-ring enol phosphate with a highly congested M-ring, and silica gel-mediated epoxide ring opening to form the J-ring. Comparison of the nuclear magnetic resonance spectroscopic data for the synthesized fragment with those for the natural product provided support for the formerly assigned structure of the N-ring in the right-hand terminal of C-CTX-1.
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Affiliation(s)
- Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Japan
| | - Kotaro Iwasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Japan
| | - Keisuke Arai
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Japan
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Sasaki M, Iwasaki K, Arai K. Studies toward the Total Synthesis of Caribbean Ciguatoxin C-CTX-1: Synthesis of the LMN-Ring Fragment through Reductive Olefin Cross-Coupling. Org Lett 2018; 20:7163-7166. [PMID: 30362358 DOI: 10.1021/acs.orglett.8b03102] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Synthesis of the LMN-ring fragment of Caribbean ciguatoxin C-CTX-1, the principal causative toxin for ciguatera fish poisoning around the Caribbean Sea areas, is described. The key feature of the synthesis is the stereoselective introduction of an angular methyl group on the sterically encumbered seven-membered M-ring by the application of a hydrogen atom transfer-based reductive olefin coupling.
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Affiliation(s)
- Makoto Sasaki
- Graduate School of Life Sciences , Tohoku University , 2-1-1 Katahira, Aoba-ku , Sendai 980-8577 , Japan
| | - Kotaro Iwasaki
- Graduate School of Life Sciences , Tohoku University , 2-1-1 Katahira, Aoba-ku , Sendai 980-8577 , Japan
| | - Keisuke Arai
- Graduate School of Life Sciences , Tohoku University , 2-1-1 Katahira, Aoba-ku , Sendai 980-8577 , Japan
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HIRAMA M. Total synthesis and related studies of large, strained, and bioactive natural products. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2016; 92:290-329. [PMID: 27725470 PMCID: PMC5243947 DOI: 10.2183/pjab.92.290] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/10/2016] [Indexed: 06/06/2023]
Abstract
Our chemical syntheses and related scientific investigations of natural products with complex architectures and powerful biological activities are described, focusing on the very large 3 nm-long polycyclic ethers called the ciguatoxins, highly strained and labile chromoprotein antitumor antibiotics featuring nine-membered enediyne cores, and extremely potent anthelmintic macrolides called the avermectins.
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Affiliation(s)
- Masahiro HIRAMA
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
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Yamashita S, Takeuchi K, Koyama T, Inoue M, Hayashi Y, Hirama M. Practical route to the left wing of CTX1B and total syntheses of CTX1B and 54-deoxyCTX1B. Chemistry 2014; 21:2621-8. [PMID: 25529606 DOI: 10.1002/chem.201405629] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Indexed: 11/07/2022]
Abstract
Ciguatoxins, the principal causative agents of ciguatera seafood poisoning, are extremely large polycyclic ethers. We report herein a reliable route for constructing the left wing of CTX1B, which possesses the acid/base/oxidant-sensitive bisallylic ether moiety, by a 6-exo radical cyclization/ring-closing metathesis strategy. This new route enabled us to achieve the second-generation total synthesis of CTX1B and the first synthesis of 54-deoxyCTX1B.
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Affiliation(s)
- Shuji Yamashita
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan).
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Szostak M, Fazakerley NJ, Parmar D, Procter DJ. Cross-Coupling Reactions Using Samarium(II) Iodide. Chem Rev 2014; 114:5959-6039. [DOI: 10.1021/cr400685r] [Citation(s) in RCA: 290] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Michal Szostak
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Neal J. Fazakerley
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Dixit Parmar
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - David J. Procter
- School
of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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Abstract
The synthesis of the novel squalene synthase inhibitor, bisabosqual A, was completed in 14 steps (longest linear sequence) from commercially available starting materials. The doubly convergent route employs a tandem 5-exo, 6-exo radical cyclization as the key step. This reaction assembles the fully functionalized tetracyclic core and introduces three stereogenic centers. Other effective transformations are the regioselective deoxygenation of an advanced enone intermediate and the chemo- and diastereoselective addition of trimethylaluminum to a ketone in the presence of esters.
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Affiliation(s)
| | - Zhou Zhou
- Department of Chemistry, Stony Brook University, New York 11794, United States
| | - Kathlyn A. Parker
- Department of Chemistry, Stony Brook University, New York 11794, United States
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Hirama M, Yamashita S, Iijima N, Shida T. Stereoselective Synthesis of Caribbean Ciguatoxin M-Ring Using [2+2] Photocyclization. HETEROCYCLES 2010. [DOI: 10.3987/com-10-s(e)61] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Aponte JC, Hammond GB, Xu B. TBAF-Mediated Aldol Reaction of β-Allenoates: Regio- and Stereoselective Synthesis of (2E,4E)-4-Carbinol Alkadienoates. J Org Chem 2009; 74:4623-5. [DOI: 10.1021/jo900567m] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- José C. Aponte
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292
| | - Gerald B. Hammond
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292
| | - Bo Xu
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292
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Sasaki M, Fuwa H. Convergent strategies for the total synthesis of polycyclic ether marine metabolites. Nat Prod Rep 2008; 25:401-26. [PMID: 18389143 DOI: 10.1039/b705664h] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Marine polycyclic ether natural products continue to fascinate chemists and biologists due to their exceptionally large and complex molecular architectures and potent and diverse biological activities. Tremendous progress has been made over the past decade toward the total synthesis of marine polycyclic ether natural products. In this area, a convergent strategy for assembling small fragments into an entire molecule always plays a key role in successful total synthesis. This review describes our efforts to develop convergent strategies for the synthesis of polycyclic ethers and their application to the total synthesis of gambierol, gymnocin-A, and brevenal, and to the partial synthesis of the central part of ciguatoxins and the nonacyclic polyether skeleton of gambieric acids.
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Affiliation(s)
- Makoto Sasaki
- Laboratory of Biostructural Chemistry, Graduate School of Life Sciences, Tohoku University, 1-1 Tsutsumidori-amamiya, Aoba-ku, Sendai 981-8555, Japan.
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