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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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Iwasaki K, Sasaki S, Kasai Y, Kawashima Y, Sasaki S, Ito T, Yotsu-Yamashita M, Sasaki M. Total Synthesis of Polycavernosides A and B, Two Lethal Toxins from Red Alga. J Org Chem 2017; 82:13204-13219. [PMID: 29124933 DOI: 10.1021/acs.joc.7b02293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polycavernosides A and B are glycosidic macrolide natural products isolated as the toxins causing fatal human poisoning by the edible red alga Gracilaria edulis (Polycavernosa tsudai). Total synthesis of polycavernosides A and B has been achieved via a convergent approach. The synthesis of the macrolactone core structure is highlighted by the catalytic asymmetric syntheses of the two key fragments using hetero-Diels-Alder reaction and Kiyooka aldol reaction as the key steps, their union through Suzuki-Miyaura coupling, and Keck macrolactonization. Finally, glycosylation with the l-fucosyl-d-xylose unit and construction of the polyene side chain through Stille coupling completed the total synthesis of polycavernosides A and B.
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Affiliation(s)
- Kotaro Iwasaki
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Satori Sasaki
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Yusuke Kasai
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Yuki Kawashima
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Shohei Sasaki
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Takanori Ito
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Mari Yotsu-Yamashita
- Graduate School of Agricultural Science, Tohoku University , 468-1 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-0845, Japan
| | - Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Fuwa H, Sasaki M. Exploiting Ruthenium Carbene-Catalyzed Reactions in Total Synthesis of Marine Oxacyclic Natural Products. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2016. [DOI: 10.1246/bcsj.20160224] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Kotha S, Ali R. Diversity Oriented Approach to Oxepine Derivatives: Further Expansion via Diels‒Alder Reaction. HETEROCYCLES 2015. [DOI: 10.3987/com-14-s(k)21] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Kerr WJ, Lindsay DM, Patel VK, Rajamanickam M. Efficient methods for enol phosphate synthesis using carbon-centred magnesium bases. Org Biomol Chem 2015; 13:10131-5. [DOI: 10.1039/c5ob01849h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Efficient conversion of ketones into enol phosphates under mild and accessible conditions has been realised using the developed methods with di-tert-butylmagnesium and bismesitylmagnesium. Optimisation of the quench protocol resulted in high yields of enol phosphates from a range of cyclohexanones and aryl methyl ketones.
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Affiliation(s)
- William J. Kerr
- Department of Pure and Applied Chemistry
- WestCHEM
- University of Strathclyde
- Glasgow
- UK
| | - David M. Lindsay
- Department of Pure and Applied Chemistry
- WestCHEM
- University of Strathclyde
- Glasgow
- UK
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Sasaki M, Fuwa H. Total synthesis and complete structural assignment of gambieric acid A, a large polycyclic ether marine natural product. CHEM REC 2014; 14:678-703. [PMID: 25092231 DOI: 10.1002/tcr.201402052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Indexed: 12/30/2022]
Abstract
More than thirty years after the discovery of polycyclic ether marine natural products, they continue to receive intense attention from the chemical, biological, and pharmacological communities because of their potent biological activities and highly complex molecular architectures. Gambieric acids are intriguing polycyclic ethers that exhibit potent antifungal activity with minimal toxicity against mammals. Despite the recent advances in the synthesis of this class of natural products, gambieric acids remain unconquered due to their daunting structural complexity, which poses a formidable synthetic challenge to organic chemists. This paper reviews our long-term studies on the total synthesis, complete configurational reassignment, and structure-activity relationships of gambieric acid A over the last decade.
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Affiliation(s)
- Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
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Suga Y, Fuwa H, Sasaki M. Stereoselective Synthesis of Medium-Sized Cyclic Ethers: Application of C-Glycosylation Chemistry to Seven- to Nine-Membered Lactone-Derived Thioacetals and Their Sulfone Counterparts. J Org Chem 2014; 79:1656-82. [DOI: 10.1021/jo4025545] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Yuto Suga
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Haruhiko Fuwa
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Ishigai K, Fuwa H, Hashizume K, Fukazawa R, Cho Y, Yotsu-Yamashita M, Sasaki M. Total synthesis and biological evaluation of (+)-gambieric acid A and its analogues. Chemistry 2013; 19:5276-88. [PMID: 23554126 DOI: 10.1002/chem.201204303] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 02/09/2013] [Indexed: 11/06/2022]
Abstract
In this study, we report the first total synthesis and complete stereostructure of gambieric acid A, a potent antifungal polycyclic ether metabolite, in detail. The A/B-ring exocyclic enol ether 32 was prepared through a Suzuki-Miyaura coupling of the B-ring vinyl iodide 18 and the alkylborate 33 and subsequent closure of the A-ring by using diastereoselective bromoetherification as the key transformation. Suzuki-Miyaura coupling of 32 with acetate-derived enol phosphate 49, followed by ring-closing metathesis of the derived diene, produced the D-ring. Subsequent closure of the C-ring through a mixed thioacetalization completed the synthesis of the A/BCD-ring fragment 8. The A/BCD- and F'GHIJ-ring fragments (i.e., 8 and 9) were assembled through Suzuki-Miyaura coupling. The C25 stereogenic center was elaborated by exploiting the intrinsic conformational property of the seven-membered F'-ring. After the oxidative cleavage of the F'-ring, the E-ring was formed as a cyclic mixed thioacetal (i.e., 70) and then stereoselectively allylated by using glycosylation chemistry. Ring-closing metathesis of the diene 3 thus obtained closed the F-ring and completed the polycyclic ether skeleton. Finally, the J-ring side chain was introduced by using a Julia-Kocienski olefination in the presence of CeCl3 to complete the total synthesis of gambieric acid A (1), thereby unambiguously establishing its complete stereostructure. The present total synthesis enabled us to evaluate the antifungal and antiproliferative activities of 1 and several synthetic analogues.
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Affiliation(s)
- Kazuya Ishigai
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Kasai Y, Ito T, Sasaki M. Total Synthesis of (−)-Polycavernoside A: Suzuki–Miyaura Coupling Approach. Org Lett 2012; 14:3186-9. [DOI: 10.1021/ol301278e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yusuke Kasai
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Takanori Ito
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Makoto Sasaki
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Alonso E, Fuwa H, Vale C, Suga Y, Goto T, Konno Y, Sasaki M, LaFerla FM, Vieytes MR, Giménez-Llort L, Botana LM. Design and synthesis of skeletal analogues of gambierol: attenuation of amyloid-β and tau pathology with voltage-gated potassium channel and N-methyl-D-aspartate receptor implications. J Am Chem Soc 2012; 134:7467-79. [PMID: 22475455 DOI: 10.1021/ja300565t] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Gambierol is a potent neurotoxin that belongs to the family of marine polycyclic ether natural products and primarily targets voltage-gated potassium channels (K(v) channels) in excitable membranes. Previous work in the chemistry of marine polycyclic ethers has suggested the critical importance of the full length of polycyclic ether skeleton for potent biological activity. Although we have previously investigated structure-activity relationships (SARs) of the peripheral functionalities of gambierol, it remained unclear whether the whole polycyclic ether skeleton is needed for its cellular activity. In this work, we designed and synthesized two truncated skeletal analogues of gambierol comprising the EFGH- and BCDEFGH-rings of the parent compound, both of which surprisingly showed similar potency to gambierol on voltage-gated potassium channels (K(v)) inhibition. Moreover, we examined the effect of these compounds in an in vitro model of Alzheimer's disease (AD) obtained from triple transgenic (3xTg-AD) mice, which expresses amyloid beta (Aβ) accumulation and tau hyperphosphorylation. In vitro preincubation of the cells with the compounds resulted in significant inhibition of K(+) currents, a reduction in the extra- and intracellular levels of Aβ, and a decrease in the levels of hyperphosphorylated tau. In addition, pretreatment with these compounds reduced the steady-state level of the N-methyl-D-aspartate (NMDA) receptor subunit 2A without affecting the 2B subunit. The involvement of glutamate receptors was further suggested by the blockage of the effect of gambierol on tau hyperphosphorylation by glutamate receptor antagonists. The present study constitutes the first discovery of skeletally simplified, designed polycyclic ethers with potent cellular activity and demonstrates the utility of gambierol and its synthetic analogues as chemical probes for understanding the function of K(v) channels as well as the molecular mechanism of Aβ metabolism modulated by NMDA receptors.
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Affiliation(s)
- Eva Alonso
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, Lugo, Spain
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Fuwa H. Total Synthesis of Tetrahydropyran-Containing Natural Products Exploiting Intramolecular Oxa-Conjugate Cyclization. HETEROCYCLES 2012. [DOI: 10.3987/rev-12-730] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ebine M, Fuwa H, Sasaki M. Total synthesis of (-)-brevenal: a streamlined strategy for practical synthesis of polycyclic ethers. Chemistry 2011; 17:13754-61. [PMID: 22052481 DOI: 10.1002/chem.201101437] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 08/08/2011] [Indexed: 11/09/2022]
Abstract
We describe a streamlined strategy for the practical synthesis of trans-fused polycyclic ethers and its application to a concise total synthesis of (-)-brevenal, a new pentacyclic polyether natural product with intriguing biological activities. The B-, D-, and E-rings were constructed by TEMPO/PhI(OAc)(2)-mediated oxidative lactonization of the corresponding 1,6-diols, with minimal need for manipulation of oxygen functionalities. The B- and E-ring lactones were appropriately functionalized by Suzuki-Miyaura coupling of lactone-derived enol phosphates and subsequent stereoselective hydroboration. The A-ring was formed by our mixed thioacetalization methodology. The AB- and DE-ring fragments were assembled through Suzuki-Miyaura coupling, and the C-ring was forged in the same manner as that for the A-ring. More than two grams of the pentacyclic polyether core of (-)-brevenal have been synthesized by the synthetic route developed in this study.
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Affiliation(s)
- Makoto Ebine
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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Fuwa H, Ebine M, Sasaki M. Recent Applications of the Suzuki-Miyaura Cross-coupling to Complex Polycyclic Ether Synthesis. J SYN ORG CHEM JPN 2011. [DOI: 10.5059/yukigoseikyokaishi.69.1251] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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