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Substrate Generation for Endonucleases of CRISPR/Cas Systems
Published on: September 8, 2012
Decarboxylative Claisen condensation catalyzed by in vitro selected ribozymes
Youngha Ryu1, Kil-Joong Kim, Charles A Roessner
1Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
Chemical Communications (Cambridge, England)
|March 22, 2006
Abstract:
The in vitro selection of RNAs catalyzing the decarboxylative Claisen condensation provides evidence for the synthesis of fatty acids, the building blocks of lipids and membranes, in the "RNA world".
Related Concept Videos
02:47Ribozymes
The term ribozyme is used for RNA that can act as an enzyme. Ribozymes are mainly found in selected viruses, bacteria, plant organelles, and lower eukaryotes. Ribozymes were first discovered in 1982 when Tom Cech’s laboratory observed Group I introns acting as enzymes. This was shortly followed by the discovery of another ribozyme, Ribonulcease P, by Sid Altman’s laboratory. Both Cech and Altman received the Nobel Prize in chemistry in 1989 for their work on ribozymes.
Ribozymes can be...
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02:47Ribozymes
The term ribozyme is used for RNA that can act as an enzyme. Ribozymes are mainly found in selected viruses, bacteria, plant organelles, and lower eukaryotes. Ribozymes were first discovered in 1982 when Tom Cech’s laboratory observed Group I introns acting as enzymes. This was shortly followed by the discovery of another ribozyme, Ribonulcease P, by Sid Altman’s laboratory. Both Cech and Altman received the Nobel Prize in chemistry in 1989 for their work on ribozymes.
Ribozymes can be...
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01:08Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...
01:33Aldol Condensation vs Claisen Condensation
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A base-promoted condensation between ester molecules to produce a ꞵ-ketoester is known as the Claisen condensation. In the presence of a base, both reactions involve deprotonation of the acidic α hydrogen to produce the corresponding enolates. The nucleophilic enolates attack their respective nonenolized carbonyl compound forming a tetrahedral intermediate.
01:24Esters to β-Ketoesters: Claisen Condensation Overview
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It is a nucleophilic acyl substitution reaction wherein one of the ester molecules, upon deprotonation by the base, forms a nucleophilic enolate ion, while the other molecule serves as an electrophile.
01:18β-Dicarbonyl Compounds via Crossed Claisen Condensations
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.