不对称的欧和提鲁卡的总合成
Joshua M Nicholson1, Glenn C Micalizio1
1Department of Chemistry, Burke Laboratory, Dartmouth College, Hanover, New Hampshire 03755, United States.
Organic letters
|July 21, 2023
概括
研究人员使用现代立体选择方法实现了第一个不对称的euphol和tirucallol新合成. 这种新的方法绕过了传统的聚烯循环,提供了对复杂自然产品的高效访问.
科学领域:
- 有机化学 有机化学
- 自然产品的合成自然产品的合成
- 立体选择性合成 立体选择性合成
背景情况:
- 像欧和蒂鲁卡兰这样的四环三类化合物是复杂的自然产物.
- 以前的合成通常依赖于生物模拟聚环化策略.
- 这些系统的高效和立体控制的总合成仍然是一个挑战.
研究的目的:
- 开发第一个不对称的 de novo 合成 euphol 和 tirucallane.
- 建立一个与仿生方法不同的新型合成路线.
- 为了证明立体定义四元中心的高效建造.
主要方法:
- 采用散列选择性Friedel-Crafts类型的循环,以形成具有C9四元中心的四环.
- 采用序列立体特异的1,2-基转移 (C9 → C10和C15 → C14) 来安装关键四分位中心.
- 通过对D环enone的后期立体选择性并联添加,引入了C17侧链.
主要成果:
- 通过新的不对称路径成功合成了enantiodefined euphane和tirucallane系统.
- 在不到20个线性步骤中从Hajos-Parrish衍生基中实现合成.
- 在每个合成过程中将染色学操作最小化为15个步骤.
结论:
- 这些代表了首次报告的euphane和tirucallane系统的de novo不对称合成.
- 开发的战略为复杂的天然产品合成提供了一个强大的替代生物仿真方法.
- 合成的简洁和刻板选择性强调了现代有机化学的进步.
相关概念视频
02:29Ethers from Alcohols: Alcohol Dehydration and Williamson Ether Synthesis
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Overview
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
Ethers can be prepared from organic compounds by various methods. Some of them are discussed below,
Preparation of Ethers by Alcohol Dehydration
In this method, in the presence of protic acids, alcohol dehydrates to produce alkenes and ethers under different conditions. For example, in the presence of sulphuric acid, dehydration of ethanol at 413 K yields ethoxyethane, whereas it yields ethene at 443 K.
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01:17Thermal Electrocyclic Reactions: Stereochemistry
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The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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01:14Alkylation of β-Diester Enolates: Malonic Ester Synthesis
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Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
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01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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01:24[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement
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The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state.
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01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
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Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
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