Related Experiment Video
Updated: Jul 5, 2026
13:05
Enzymatic Synthesis of Epoxidized Metabolites of Docosahexaenoic, Eicosapentaenoic, and Arachidonic Acids
Published on: June 28, 2019
A strategy for position-selective epoxidation of polyprenols
Vijay Gnanadesikan1, E J Corey
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Journal of the American Chemical Society
|May 23, 2008
Summary
Researchers developed a new method for site-selective epoxidation of polyolefinic isoprenoid alcohols using an internal control element for intramolecular reactions. This strategy efficiently targets specific double bonds in polyprenols.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Polymer Chemistry
Background:
- Polyolefinic isoprenoid alcohols are important natural products and synthetic intermediates.
- Selective functionalization of polyolefins remains a challenge in organic synthesis.
- Epoxidation is a key transformation for introducing oxygen-containing functionalities.
Purpose of the Study:
- To develop an efficient and site-selective epoxidation strategy for polyolefinic isoprenoid alcohols.
- To utilize an internal control element for directing intramolecular reactions.
- To demonstrate the applicability of the method to various polyprenol substrates.
Main Methods:
- Development of a novel epoxidation strategy employing an internal control element.
- Application of the strategy to a series of polyisoprenoid alcohols (polyprenols).
- Optimization of substrate concentration at 0.5 mM for efficient reaction.
Main Results:
- Achieved efficient site-selective epoxidation of polyolefinic isoprenoid alcohols.
- Demonstrated successful intramolecular reaction control.
- Directed epoxidation at specific double bonds (four or five positions away) in terminal polyprenols.
Conclusions:
- The developed strategy offers an effective route for selective epoxidation of polyprenols.
- The internal control element is crucial for achieving site-selectivity.
- This method provides a valuable tool for the synthesis of complex isoprenoid derivatives.
Related Concept Videos
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
02:57Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
02:24Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.