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Highly efficient route for enantioselctive preparation of chlorohydrins via dynamic kinetic resolution
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2008 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 21, 4807-4810 p.Article in journal (Refereed) Published
Abstract [en]

Dynamic kinetic resolution (DKR) of various aromatic chlorohydrins with the use of Pseudomonas cepacia lipase (PS-C “Amano” II) and ruthenium catalyst 1 afforded chlorohydrin acetates in high yields and high enantiomeric excesses. These optically pure chlorohydrin acetates are useful synthetic intermediates and can be transformed to a range of important chiral compounds.

Place, publisher, year, edition, pages
2008. Vol. 10, no 21, 4807-4810 p.
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-15314DOI: 10.1021/ol801749zISI: 000260534500025OAI: oai:DiVA.org:su-15314DiVA: diva2:181834
Available from: 2009-01-05 Created: 2009-01-05 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Asymmetric transformation of ß- and γ-functionalized alcohols: Study of combined ruthenium-catalyzed racemization and enzymatic resolution
Open this publication in new window or tab >>Asymmetric transformation of ß- and γ-functionalized alcohols: Study of combined ruthenium-catalyzed racemization and enzymatic resolution
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The major part of this thesis describes the asymmetric synthesis of β- and γ-amino alcohols through the combination of ruthenium catalyzed racemization and enzymatic kinetic resolution.

The dynamic kinetic resolution, DKR, protocol for chlorohydrins was improved by employing Bäckvall’s catalyst, which is a base activated racemization catalyst, in combination with Burkholderia cepacia lipase. These optimized conditions broadened the substrate scope and improved the yields and ee’s of the obtained chlorohydrin acetates. The utility of the method was demonstrated in the synthesis of (S)-salbutamol.

In the second part of the thesis, DKR was utilized in the enantio-determining step of the total synthesis of (R)-duloxetine. Optimized DKR conditions, combining Bäckvall’s catalyst together with Candida antarctica lipase B, afforded a β-cyano acetate in high yield and ee. (R)-Duloxetine was accessible through synthetic alterations of the enantioenriched β-cyano acetate in high overall yield.

A dynamic kinetic asymmetric transformation, DYKAT, protocol to obtain enantio- and diastereomerically pure γ-amino alcohols was developed. In a first step N-Boc-aminoketones were obtained in high enantiomeric purity through a proline-catalyzed Mannich reaction. Subsequent in situ reduction coupled with a highly efficient DYKAT yielded γ-amino acetates in high dr and ee. The γ-amino alcohols were available through simple hydrolysis/deprotection with retained stereochemistry.

In the final part of the thesis a heterogeneous bifunctional catalytic system is reported, which combines the catalytic properties of transition metal-catalyzed racemization with enzymatic acylation. A novel ruthenium-phosphonate complex was synthesized and then covalently anchored to the active site of solid supported Candida antarctica lipase B. The partially inhibited beads proved to be catalytically active both in racemization as well as enzymatic acylation.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. 91 p.
Keyword
Kinetic resolution, dynamic kinetic resolution, kinetic asymmetric transformation, dynamic kinetic asymmetric transformation, enzyme catalysis, racemization, asymmetric synthesis, chlorohydrin, cyano acetate, amino alcohol, metalloenzyme, bifunctional catalytic system
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-56947 (URN)978-91-7447-307-0 (ISBN)
Public defence
2011-06-10, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Epub ahead of print.Available from: 2011-05-13 Created: 2011-05-02 Last updated: 2011-06-15Bibliographically approved
2. Ruthenium-Catalyzed Hydrogen Transfer Reactions: Mechanistic Studies and Chemoenzymatic Dynamic Kinetic Resolutions
Open this publication in new window or tab >>Ruthenium-Catalyzed Hydrogen Transfer Reactions: Mechanistic Studies and Chemoenzymatic Dynamic Kinetic Resolutions
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main focus of this thesis lies on transition metal-catalyzed hydrogen transfer reactions. In the first part of the thesis, the mechanism for racemization of sec-alcohols with a ruthenium complex, Ru(CO)2Cl(η5-C5Ph5) was studied.

The reaction between 5-hexen-2-ol and Ru(CO)2(Ot-Bu)(η5-C5Ph5) was studied with the aim to elucidate the origin of the slow racemization observed for this sec-alcohol. Two diastereomers of an alkoxycarbonyl complex, which has the double bond coordinated to ruthenium, were characterized by NMR and in situ FT-IR spectroscopy. The observed inhibition of the rate of racemization for substrates with double bonds provided further confirmation of the importance of a free coordination site on ruthenium for β-hydride elimination. Furthermore, we observed that CO exchange, monitored by 13C NMR using 13CO, occurs with both the precatalyst, Ru(CO)2Cl(η5-C5Ph5), and the active catalytic intermediate, Ru(CO)2(Ot-Bu)(η5-C5Ph5). It was also found that added CO has an inhibitory effect on the rate of racemization of (S)-1-phenylethanol. Both these observations provide strong support for reversible CO dissociation as a key step in the racemization mechanism.

In the second part of this thesis, Ru(CO)2Cl(η5-C5Ph5) was combined with an enzymatic resolution catalyzed by a lipase, leading to several efficient dynamic kinetic resolutions (DKR). DKR of exocyclic allylic alcohols afforded the corresponding acetates in high yields and with excellent enantiomeric excess (ee). The products were utilized as synthetic precursors for α-substituted ketones and lactones. DKR of a wide range of homoallylic alcohols afforded the products in good to high yields and with high ee. The homoallylic acetates were transformed into 5,6-dihydropyran-2-ones in a short reaction sequence. Furthermore, DKR of a wide range of aromatic β-chloroalcohols afforded the products in high yields and with excellent ee. The β-chloro acetates were further transformed into chiral epoxides.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. 84 p.
Keyword
Hydrogen transfer, ruthenium catalysis, kinetic resolution, dynamic kinetic resolution, racemization, asymmetric synthesis
National Category
Natural Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-89263 (URN)978-91-7447-706-1 (ISBN)
Public defence
2013-05-24, Magnélisalen, Kemiska Övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Mansucript.

Available from: 2013-04-18 Created: 2013-04-17 Last updated: 2013-11-06Bibliographically approved

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