Asymmetric total synthesis of clavolonine

Kenji Nakahara1, Kie Hirano, Ryota Maehata

  • 1Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka, 565-0871 Japan.

Organic Letters
|March 11, 2011
PubMed

Related Concept Videos

Esters to β-Ketoesters: Claisen Condensation Mechanism01:08

Esters 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...
Aldol Condensation vs Claisen Condensation01:33

Aldol 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.
Ketones with Nonenolizable Aromatic Aldehydes: Claisen–Schmidt Condensation01:01

Ketones with Nonenolizable Aromatic Aldehydes: Claisen–Schmidt Condensation

Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the presence of an aqueous base forms a single crossed product. This reaction is referred to as Claisen–Schmidt condensation.
As the self-condensation of ketones is generally not favored in basic conditions, the self-condensed products do not form in the reaction between ketones and benzaldehyde. The general reaction of Claisen–Schmidt condensation is...
[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement01:24

[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement

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.
Esters to β-Ketoesters: Claisen Condensation Overview01:24

Esters 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.
Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization01:13

Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization

Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.