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1,3-Dipolar Cycloadditions of Azomethine Ylides to Aldehydes: Synthesis of α-Amino-β-hydroxy Esters
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
(English)Manuscript (Other academic)
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-7405OAI: oai:DiVA.org:kth-7405DiVA: diva2:12423
Note
QC 20100820Available from: 2007-08-23 Created: 2007-08-23 Last updated: 2010-08-20Bibliographically approved
In thesis
1. Stereoselective Synthesis of Amino Alcohols: Applications to Natural Product Synthesis
Open this publication in new window or tab >>Stereoselective Synthesis of Amino Alcohols: Applications to Natural Product Synthesis
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis is divided into four separate parts with amino alcohols as the common feature.

The first part of the thesis describes the development of an efficient three-component approach to the synthesis of α-hydroxy-β-amino esters. Utilizing a highly diastereoselective Rh(II)-catalyzed 1,3-dipolar cycloaddition of carbonyl ylides to various aldimines, syn-α-hydroxy-β-amino esters are formed in high yields and excellent diastereoselectivities. An asymmetric version was also developed by employing chiral α-methylbenzyl imines as dipolarophiles yielding enantiomerically pure syn-α-hydroxy-β-amino esters. This methodology was also applied on a short asymmetric synthesis of the paclitaxel side-chain as well as in an asymmetric synthetic approach towards the proteasome inhibitor omuralide. Furthermore, the use of chiral Rh(II) carboxylates furnishes the syn-α-hydroxy-β-amino esters in moderate enantioselectivity (er up to 82:18), which indicates that the reaction proceeds via a metal-associated carbonyl ylide.

The second part describes the development of a 1,3-dipolar cycloaddition reaction of azomethine ylides to aldehydes for the synthesis of α-amino-β-hydroxy esters. Different methods for the generation of the ylides, including Vedejs’ oxazole methology and an Ag(I)/phosphine-catalyzed approach have been evaluated. The best results were obtained with the Ag(I)/phosphine approach, which yielded the desired α-amino-β-hydroxy ester in 68% yield and 3.4:1 syn:anti-selectivity.

The last two parts deals with the total synthesis of the amino alcohol-containing natural products D-erythro-sphingosine and (−)-stemoamide. The key transformation in the sphingosine synthesis is a cross-metathesis reaction for the assembly of the polar head group and the aliphatic chain. In the stemoamide synthesis, the key feature is an iodoboration/Negishi/RCM-sequence for the construction of the β,γ-unsaturated azepine core of stemoamide followed by a stereoselective bromolactonization/1,4-reduction strategy for the installation of the requisite C8-C9 trans-stereochemistry.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 71 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:52
Keyword
Amino alcohol, asymmetric 1.3-dipolar cycloaddition, azomethine ylide, carbenoid, carbonyl ylide, cross-metathesis, omuralide, oxazolidine, rhodium, sphingosine, stemoamide, stereoselective synthesis, total synthesis.
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-4472 (URN)978-91-7178-734-7 (ISBN)
Public defence
2007-09-14, F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100820Available from: 2007-08-23 Created: 2007-08-23 Last updated: 2010-08-20Bibliographically approved

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