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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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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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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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