由于eudesm-5-yl碳酸的循环形成,对四烯多样性的物理约束
B Andes Hess1, Lidia Smentek, Joseph P Noel
1Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States. b.andes.hess@vanderbilt.edu
Journal of the American Chemical Society
|July 1, 2011
概括
量子力学揭示了植物烯如何重新排列. 环替代剂会影响烯结构,这解释了为什么一些天然化合物尽管具有热力学优势,但却很罕见.
科学领域:
- 生物化学 生物化学
- 有机化学 有机化学
- 计算化学计算化学
背景情况:
- 烯是具有多样性结构的天然产品,对植物防御至关重要.
- 索拉属植物从一个常见的碳酸介质中产生埃雷莫菲兰和螺旋维.
- 共享这种中间体的螺旋体骨在自然界中很罕见,构成了生物合成的难题.
研究的目的:
- 在基生物合成中研究替代碳酸重排的物理基础.
- 确定环替代剂如何影响烯骨分布.
- 解释一下理论上和观察到的自然丰富度之间的差异.
主要方法:
- 量子力学 (QM) 分析用于计算碳酸构造,能量和过渡状态.
- 研究eudesm-5-yl碳化和简化的脱系统.
- 对二面角的分析,以确定重新排列的形状值.
主要成果:
- 环替代物扩大了形状空间,但可以在固态上阻碍重新排列.
- 甲迁移以形成螺旋化合物在热力学上有利于eudesm-5-yl碳酸.
- 计算的热力学有利性与某些基骨的自然丰度较低形成鲜明对比.
结论:
- 由环置换剂控制的形状灵活性和硬质障碍决定了骨的结果.
- 热力学稳定性不能完全预测自然产品的丰富性.
- 这些发现提供了关于聚烯合成酶催化机制和天然产品发现的见解.
相关概念视频
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
Thermal Electrocyclic Reactions: Stereochemistry
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.
Stability of Conjugated Dienes
Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Stereoisomerism of Cyclic Compounds
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...


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