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Wang Y, Nagai T, Watanabe I, Hagiwara K, Inoue M. Total Synthesis of Euonymine and Euonyminol Octaacetate. J Am Chem Soc 2021; 143:21037-21047. [PMID: 34870420 DOI: 10.1021/jacs.1c11038] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Euonymine (1) and euonyminol octaacetate (2) share the core structure of euonyminol (3), the most hydroxylated member of the dihydro-β-agarofuran family. In 2, eight of the nine hydroxy groups of 3 are acetylated, and 1 has six acetyl groups and a 14-membered bislactone comprising a pyridine dicarboxylic acid with two methyl groups. The different acylation patterns provide distinct biological activities: 1 and 2 display anti-HIV and P-glycoprotein inhibitory effects, respectively. The 11 contiguous stereocenters and 9 oxygen functionalities of the ABC-ring system of 1 and 2 represent a formidable challenge, which is further heightened by the macrocyclic structure of 1. Here we disclose an efficient synthetic strategy for enantioselective total synthesis of 1 and 2. Starting from (R)-glycerol acetonide, we constructed the B-ring by an Et3N-accelerated Diels-Alder reaction, the C-ring by intramolecular iodoetherification, and the A-ring by ring-closing olefin metathesis. The 10 stereocenters were installed through a series of substrate-controlled stereoselective C-C and C-O bond formations by exploiting the three-dimensional structures of judiciously designed substrates. These newly developed reaction sequences led to protected euonyminol 5, which served as a common intermediate for assembling 1 and 2. Global deprotection of 5 and subsequent acetylation produced 2. Alternatively, the discriminative protective groups of 5 allowed for site-selective bis-esterification to generate bislactone. Combining [3 + 2]-cycloaddition and reductive desulfurization introduced the last remaining stereocenters of the two methyl groups on the macrocycle. Finally, deprotection and acetylation gave rise to fully synthetic 1 for the first time.
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Affiliation(s)
- Yinghua Wang
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Toshiya Nagai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Itsuki Watanabe
- 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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2
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Tomanik M, Xu Z, Guo F, Wang Z, Yang KR, Batista VS, Herzon SB. Development of an Enantioselective Synthesis of (-)-Euonyminol. J Org Chem 2021; 86:17011-17035. [PMID: 34784213 DOI: 10.1021/acs.joc.1c02167] [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
We detail the development of the first enantioselective synthetic route to euonyminol (1), the most heavily oxidized member of the dihydro-β-agarofuran sesquiterpenes and the nucleus of the macrocyclic alkaloids known as the cathedulins. Key steps in the synthetic sequence include a novel, formal oxyalkylation reaction of an allylic alcohol by [3 + 2] cycloaddition; a tandem lactonization-epoxide opening reaction to form the trans-C2-C3 vicinal diol residue; and a late-stage diastereoselective trimethylaluminum-mediated α-ketol rearrangement. We report an improved synthesis of the advanced unsaturated ketone intermediate 64 by means of a 6-endo-dig radical cyclization of the enyne 42. This strategy nearly doubled the yield through the intermediate steps in the synthesis and avoided a problematic inversion of stereochemistry required in the first-generation approach. Computational studies suggest that the mechanism of this transformation proceeds via a direct 6-endo-trig cyclization, although a competing 5-exo-trig cyclization, followed by a rearrangement, is also energetically viable. We also detail the challenges associated with manipulating the oxidation state of late-stage intermediates, which may inform efforts to access other derivatives such as 9-epi-euonyminol or 8-epi-euonyminol. Our successful synthetic strategy provides a foundation to synthesize the more complex cathedulins.
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Affiliation(s)
- Martin Tomanik
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Zhi Xu
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Facheng Guo
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Zechun Wang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Ke R Yang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Seth B Herzon
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, United States
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3
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Zhang XM, Li BS, Wang SH, Zhang K, Zhang FM, Tu YQ. Recent development and applications of semipinacol rearrangement reactions. Chem Sci 2021; 12:9262-9274. [PMID: 34349896 PMCID: PMC8314203 DOI: 10.1039/d1sc02386a] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/04/2021] [Indexed: 11/21/2022] Open
Abstract
As has been well-recognized, semipinacol rearrangement functions as an exceptionally useful methodology in the synthesis of β-functionalized ketones, creation of quaternary carbon centers, and construction of challenging carbocycles. Due to their versatile utilities in organic synthesis, development of novel rearrangement reactions has been a vibrant topic that continues to shape the research field. Recent breakthroughs in novel electrophiles, tandem processes, and enantioselective catalytic transformations further enrich the toolbox of this chemistry and spur the strategic applications of this methodology in natural product synthesis. These achievements will be discussed in this minireview.
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Affiliation(s)
- Xiao-Ming Zhang
- State Key Laboratory of Applied Organic Chemistry and School of Pharmacy, Lanzhou University Lanzhou 730000 P. R. China
| | - Bao-Sheng Li
- School of Chemistry and Chemical Engineering, Chongqing University Chongqing 400030 P. R. China
| | - Shao-Hua Wang
- State Key Laboratory of Applied Organic Chemistry and School of Pharmacy, Lanzhou University Lanzhou 730000 P. R. China
| | - Kun Zhang
- School of Biotechnology and Health Sciences, Wuyi University Jiangmen Guangdong 529020 P. R. China
| | - Fu-Min Zhang
- State Key Laboratory of Applied Organic Chemistry and School of Pharmacy, Lanzhou University Lanzhou 730000 P. R. China
| | - Yong-Qiang Tu
- State Key Laboratory of Applied Organic Chemistry and School of Pharmacy, Lanzhou University Lanzhou 730000 P. R. China
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