1
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Tichvon C, Zviagin E, Surma Z, Nagorny P. Synthesis of Bufadienolide Cinobufagin via Late-Stage Singlet Oxygen Oxidation/Rearrangement Approach. Org Lett 2024; 26:2445-2450. [PMID: 38488174 PMCID: PMC10980571 DOI: 10.1021/acs.orglett.4c00625] [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] [Indexed: 04/01/2024]
Abstract
This manuscript describes a concise synthesis of cinobufagin, a natural steroid of the bufadienolide family, from readily available dehydroepiandrosterone (DHEA), as well as its α5-epimer derived from 3-epi-andosterone. This synthesis features expedient installation of the 17β-pyrone moiety with the 14β,15β-epoxide and the 16β-acetoxy group using a photochemical regioselective singlet oxygen [4 + 2] cycloaddition followed by CoTPP-promoted in situ endoperoxide rearrangement to provide a 14β,16β-bis-epoxide in 64% yield with a 1.6:1 d.r. This β,β-bis-epoxide intermediate was subsequently subjected to a regioselective scandium(III) trifluoromethanesulfonate catalyzed House-Meinwald rearrangement to establish the 17β-configuration. The synthesis of cinobufagin is achieved in 12 steps (LLS) and 7.6% overall yield, and we demonstrate that it could be used as a platform for the subsequent medicinal chemistry exploration of cinobufagin analogs such as cinobufagin 5α-epimer.
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Affiliation(s)
- Colin Tichvon
- Chemistry Department, University of Michigan, 930 N. University Ave. Ann Arbor, MI 48109
| | - Eugene Zviagin
- Chemistry Department, University of Michigan, 930 N. University Ave. Ann Arbor, MI 48109
| | - Zoey Surma
- Chemistry Department, University of Michigan, 930 N. University Ave. Ann Arbor, MI 48109
| | - Pavel Nagorny
- Chemistry Department, University of Michigan, 930 N. University Ave. Ann Arbor, MI 48109
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2
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Watanabe A, Nagatomo M, Hirose A, Hikone Y, Kishimoto N, Miura S, Yasutake T, Abe T, Misumi S, Inoue M. Total Syntheses of Phorbol and 11 Tigliane Diterpenoids and Their Evaluation as HIV Latency-Reversing Agents. J Am Chem Soc 2024; 146:8746-8756. [PMID: 38486375 DOI: 10.1021/jacs.4c01589] [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: 03/28/2024]
Abstract
Tigliane diterpenoids possess exceptionally complex structures comprising common 5/7/6/3-membered ABCD-rings and disparate oxygen functionalities. While tiglianes display a wide range of biological activities, compounds with HIV latency-reversing activity can eliminate viral reservoirs, thereby serving as promising leads for new anti-HIV agents. Herein, we report collective total syntheses of phorbol (13) and 11 tiglianes 14-24 with various acylation patterns and oxidation states, and their evaluation as HIV latency-reversing agents. The syntheses were strategically divided into five stages to increase the structural complexity. First, our previously established sequence enabled the expeditious preparation of ABC-tricycle 9 in 15 steps. Second, hydroxylation of 9 and ring-contractive D-ring formation furnished phorbol (13). Third, site-selective attachment of two acyl groups to 13 produced four phorbol diesters 14-17. Fourth, the oxygen functionalities were regio- and stereoselectively installed to yield five tiglianes 18-22. Fifth, further oxidation to the most densely oxygenated acerifolin A (23) and tigilanol tiglate (24) was realized through organizing a 3D shape of the B-ring. Assessment of the HIV latency-reversing activities of the 12 tiglianes revealed seven tiglianes (14-17 and 22-24) with 20- to 300-fold improved efficacy compared with prostratin (12), a representative latency-reversing agent. Therefore, the robust synthetic routes to a variety of tiglianes with promising activities devised in this study provide opportunities for advancing HIV eradication strategies.
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Affiliation(s)
- Ayumu Watanabe
- 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
| | - Akira Hirose
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yuto Hikone
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Naoki Kishimoto
- Department of Environmental and Molecular Health Sciences, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Satoshi Miura
- Department of Environmental and Molecular Health Sciences, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Tae Yasutake
- Department of Environmental and Molecular Health Sciences, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Towa Abe
- Department of Environmental and Molecular Health Sciences, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Shogo Misumi
- Department of Environmental and Molecular Health Sciences, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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3
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Tomkiel AM, Majewski AD, Siergiejczyk L, Morzycki JW. Montmorillonite Catalyzed Synthesis of Novel Steroid Dimers. Molecules 2023; 28:7068. [PMID: 37894547 PMCID: PMC10609449 DOI: 10.3390/molecules28207068] [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: 09/28/2023] [Revised: 10/10/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
The reactions of sterols (androst-5-en-3β-ol-17-one, diosgenin, and cholesterol) and their tosylates with hydroquinone aimed at the synthesis of O,O-1,4-phenylene-linked steroid dimers were studied. The reaction course strongly depended on the conditions used. The study has shown that the major reaction products are the elimination products and unusual steroid dimers resulting from the nucleophilic attack of the hydroquinone C2 carbon atom on the steroid C3 position, followed by an intramolecular addition to the C5-C6 double bond. A different reaction course was observed when montmorillonite K10 was used as a catalyst. The reaction of androst-5-en-3β-ol-17-one under the promotion of this catalyst afforded the O,O-1,4-phenylene-linked steroid dimer in addition to the disteroidal ether. The formation of the latter compound was suppressed by using 3-tosylate as a substrate instead of the free sterol. The reactions of androst-5-en-3β-ol-17-one tosylate and cholesteryl tosylate with hydroquinone catalyzed by montmorillonite K10 carried out under optimized conditions afforded the desired dimers in 31% and 67% yield, respectively.
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Affiliation(s)
- Aneta M. Tomkiel
- Faculty of Chemistry, University of Bialystok, Ciołkowskiego 1K, 15-245 Bialystok, Poland; (A.D.M.); (L.S.)
| | - Adam D. Majewski
- Faculty of Chemistry, University of Bialystok, Ciołkowskiego 1K, 15-245 Bialystok, Poland; (A.D.M.); (L.S.)
- Doctoral School of Exact and Natural Sciences, University of Bialystok, Ciołkowskiego 1K, 15-245 Bialystok, Poland
| | - Leszek Siergiejczyk
- Faculty of Chemistry, University of Bialystok, Ciołkowskiego 1K, 15-245 Bialystok, Poland; (A.D.M.); (L.S.)
| | - Jacek W. Morzycki
- Faculty of Chemistry, University of Bialystok, Ciołkowskiego 1K, 15-245 Bialystok, Poland; (A.D.M.); (L.S.)
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4
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Watanabe Y, Morozumi H, Mutoh H, Hagiwara K, Inoue M. Total Synthesis of (-)-Batrachotoxin Enabled by a Pd/Ag-Promoted Suzuki-Miyaura Coupling Reaction. Angew Chem Int Ed Engl 2023; 62:e202309688. [PMID: 37582693 DOI: 10.1002/anie.202309688] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 08/11/2023] [Accepted: 08/15/2023] [Indexed: 08/17/2023]
Abstract
Batrachotoxin is an extremely potent cardio- and neurotoxic steroidal alkaloid found in certain species of frogs, birds, and beetles. The steroidal 6/6/6/5-membered carbocycle (ABCD-ring) is U-shaped and functionalized with two double bonds, a six-membered C3-hemiacetal across the AB-ring, a seven-membered oxazepane on the CD-ring, and a dimethylpyrrolecarboxy group at the D-ring carbon chain. These structural features present an unusual and formidable synthetic challenge. Herein we report a total synthesis of batrachotoxin based on a newly devised convergent strategy through a 22-step sequence. Enantiopure AB-ring and D-ring fragments were prepared and subjected to a crucial C(sp2 )-C(sp2 ) coupling reaction. Although both C(sp2 ) centers were sterically encumbered by proximal tetrasubstituted carbon atoms, Ag2 O strongly promoted the Pd(PPh3 )4 -catalyzed Suzuki-Miyaura coupling reaction at room temperature, thereby connecting the two fragments without damaging their preexisting functionalities. Subsequent treatment with t-BuOK induced Dieckmann condensation to cyclize the C-ring. The judiciously optimized functionalizations realized oxazepane formation, carbon chain extension, and pyrrole carboxylic acid condensation to deliver batrachotoxin.
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Affiliation(s)
- Yuuki Watanabe
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hisahiro Morozumi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hiroyuki Mutoh
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Koichi Hagiwara
- 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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5
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Asrorov AM, Kayumov M, Mukhamedov N, Yashinov A, Mirakhmetova Z, Huang Y, Yili A, Aisa HA, Tashmukhamedov M, Salikhov S, Mirzaakhmedov S. Toad venom bufadienolides and bufotoxins: An updated review. Drug Dev Res 2023; 84:815-838. [PMID: 37154099 DOI: 10.1002/ddr.22072] [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] [Received: 02/08/2023] [Revised: 04/14/2023] [Accepted: 04/20/2023] [Indexed: 05/10/2023]
Abstract
Bufadienolides, naturally found in toad venoms having steroid-like structures, reveal antiproliferative effects at low doses. However, their application as anticancer drugs is strongly prevented by their Na+ /K+ -ATPase binding activities. Although several kinds of research were dedicated to moderating their Na+ /K+ -ATPase binding activity, still deeper fundamental knowledge is required to bring these findings into medical practice. In this work, we reviewed data related to anticancer activity of bufadienolides such as bufalin, arenobufagin, bufotalin, gamabufotalin, cinobufotalin, and cinobufagin and their derivatives. Bufotoxins, derivatives of bufadienolides containing polar molecules mainly belonging to argininyl residues, are reviewed as well. The established structures of bufotoxins have been compiled into a one-page figure to review their structures. We also highlighted advances in the structure-modification of the structure of compounds in this class. Drug delivery approaches to target these compounds to tumor cells were discussed in one section. The issues related to extraction, identification, and quantification are separated into another section.
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Affiliation(s)
- Akmal M Asrorov
- Institute of Bioorganic Chemistry of Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
- Department of Natural Substances Chemistry, National University of Uzbekistan, Tashkent, Uzbekistan
- Shanghai Institute of Materia Medica, CAS, Shanghai, China
| | - Muzaffar Kayumov
- Institute of Bioorganic Chemistry of Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
| | - Nurkhodja Mukhamedov
- Institute of Bioorganic Chemistry of Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
| | - Ansor Yashinov
- Shanghai Institute of Materia Medica, CAS, Shanghai, China
- University of Chinese Academy of Sciences (UCAS), Beijing, China
| | - Ziyoda Mirakhmetova
- Institute of Bioorganic Chemistry of Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
| | - Yongzhuo Huang
- Shanghai Institute of Materia Medica, CAS, Shanghai, China
- University of Chinese Academy of Sciences (UCAS), Beijing, China
| | - Abulimiti Yili
- Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi, China
| | - Haji Akber Aisa
- Xinjiang Technical Institute of Physics and Chemistry, CAS, Urumqi, China
| | | | - Shavkat Salikhov
- Institute of Bioorganic Chemistry of Uzbekistan Academy of Sciences, Tashkent, Uzbekistan
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6
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Zou D, Wang Q, Chen T, Sang D, Yang T, Wang Y, Gao M, He F, Li Y, He L, Longzhu D. Bufadienolides originated from toad source and their anti-inflammatory activity. Front Pharmacol 2022; 13:1044027. [PMID: 36339575 PMCID: PMC9627299 DOI: 10.3389/fphar.2022.1044027] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 10/10/2022] [Indexed: 03/03/2024] Open
Abstract
Bufadienolide, an essential member of the C-24 steroid family, is characterized by an α-pyrone positioned at C-17. As the predominantly active constituent in traditional Chinese medicine of Chansu, bufadienolide has been prescribed in the treatment of numerous ailments. It is a specifically potent inhibitor of Na+/K+ ATPase with excellent anti-inflammatory activity. However, the severe side effects triggered by unbiased inhibition of the whole-body cells distributed α1-subtype of Na+/K+ ATPase, restrict its future applicability. Thus, researchers have paved the road for the structural alteration of desirable bufadienolide derivatives with minimal adverse effects via biotransformation. In this review, we give priority to the present evidence for structural diversity, MS fragmentation principles, anti-inflammatory efficacy, and structure modification of bufadienolides derived from toads to offer a scientific foundation for future in-depth investigations and views.
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Affiliation(s)
- Denglang Zou
- School of Life Science, Qinghai Normal University, Xining, China
- College of Pharmacy, Jinan University, Guangzhou, China
- Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China
| | - Qiqi Wang
- College of Pharmacy, Jinan University, Guangzhou, China
| | - Tao Chen
- Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China
| | - Duocheng Sang
- School of Life Science, Qinghai Normal University, Xining, China
| | - Tingqin Yang
- School of Life Science, Qinghai Normal University, Xining, China
| | - Yuhan Wang
- School of Life Science, Qinghai Normal University, Xining, China
| | - Mengze Gao
- School of Life Science, Qinghai Normal University, Xining, China
| | - Fangfang He
- School of Life Science, Qinghai Normal University, Xining, China
| | - Yulin Li
- Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China
| | - Liangliang He
- College of Pharmacy, Jinan University, Guangzhou, China
| | - Duojie Longzhu
- School of Life Science, Qinghai Normal University, Xining, China
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7
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Zhao Y, Zhang B, Sun ZQ, Zhang H, Wang W, Wang ZR, Guo ZK, Yu S, Tan RX, Ge HM. Biocatalytic C14-Hydroxylation on Androstenedione Enabled Modular Synthesis of Cardiotonic Steroids. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yang Zhao
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Bo Zhang
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Zi Qian Sun
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Hao Zhang
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Wen Wang
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Zi Ru Wang
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Zhi Kai Guo
- Key Laboratory of Biology and Genetic Resources of Tropical Crops, Ministry of Agriculture, Institute of Tropical Bioscience and Bio-technology, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
| | - Shouyun Yu
- State Key Laboratory of Analytical Chemistry for Life Science, Jiangsu Key Laboratory of Advanced Organic Materials, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Ren Xiang Tan
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Hui Ming Ge
- State Key Laboratory of Pharmaceutical Biotechnology, Institute of Functional Biomolecules, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Life Sciences, Nanjing University, Nanjing 210023, China
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Abstract
This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via three-step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl-directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and a 3.1% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with l-rhamnopyranoside-based donor 28 using a Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in a 66% yield (two steps).
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Affiliation(s)
- Zachary Fejedelem
- Chemistry Department, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| | - Nolan Carney
- Chemistry Department, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| | - Pavel Nagorny
- Chemistry Department, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
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9
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Wang YH, Zhang DH, Cao ZH, Li WL, Huang YY. A formal [3 + 3] cycloaddition of allenyl imide and activated ketones for the synthesis of tetrasubstituted 2-pyrones. RSC Adv 2021; 11:8867-8870. [PMID: 35423364 PMCID: PMC8695344 DOI: 10.1039/d0ra10686k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 02/19/2021] [Indexed: 01/03/2023] Open
Abstract
CsOH·H2O-catalyzed formal [3 + 3] cycloadditions of allenyl imide with β-ketoesters, 1,3-diketones or β-ketonitriles for the synthesis of tetrasubstituted 2-pyrone derivatives have been demonstrated. The allenyl imide was utilized as a C3-synthon, and a ketenyl intermediate was proposed via the process of 1,4-addition of carbon anion to allene followed by elimination of the 2-oxazolidinyl group. CsOH·H2O-catalyzed formal [3 + 3] cycloadditions of allenyl imide with β-ketoesters, 1,3-diketones or β-ketonitriles for the synthesis of tetrasubstituted 2-pyrone derivatives were reported.![]()
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Affiliation(s)
- Yu-Hao Wang
- Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology Wuhan 430070 China
| | - De-Hua Zhang
- Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology Wuhan 430070 China
| | - Ze-Hun Cao
- Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology Wuhan 430070 China
| | - Wang-Lai Li
- Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology Wuhan 430070 China
| | - Yi-Yong Huang
- Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology Wuhan 430070 China
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10
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Watanabe S, Nishikawa T, Nakazaki A. Total Synthesis of the Cardiotonic Steroid (+)-Cannogenol. J Org Chem 2021; 86:3605-3614. [PMID: 33538172 DOI: 10.1021/acs.joc.0c02966] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The total synthesis of (+)-cannogenol, an aglycon common to various biologically important cardiotonic glycosides, has been achieved. Synthesis of the versatile intermediate involves Mizoroki-Heck and intramolecular Diels-Alder reactions from the enantiomerically pure CD-ring segment, newly prepared in a multidecagram scale this time. Total synthesis by the site-selective transformations of the versatile intermediate demonstrated the applicability of our synthetic approach.
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Affiliation(s)
- Shogo Watanabe
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan
| | - Toshio Nishikawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan
| | - Atsuo Nakazaki
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan
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