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Synthesis of Pyragonicin
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
2005 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 7, no 13, 2779-2781 p.Article in journal (Refereed) Published
Abstract [en]

A stereocontrolled convergent synthesis of the annonaceous acetogenin pyragonicin (1) is presented. The key intermediates were accessed using asymmetric Horner-Wadsworth-Emmons (HWE) methodology. A reagent controlled zinc-mediated stereoselective coupling, joining the two highly functionalized intermediates 3 and 4, then provided the core structure.

Place, publisher, year, edition, pages
2005. Vol. 7, no 13, 2779-2781 p.
Keyword [en]
annonaceous acetogenins, epimerization, pyranicin, ring
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-6067DOI: 10.1021/ol050997gISI: 000229952100066Scopus ID: 2-s2.0-29844439833OAI: oai:DiVA.org:kth-6067DiVA: diva2:10670
Note
QC 20100921Available from: 2006-08-28 Created: 2006-08-28 Last updated: 2010-09-21Bibliographically approved
In thesis
1. Methods for Asymmetric Olefination Reactions; Development and Application to Natural Product Synthesis
Open this publication in new window or tab >>Methods for Asymmetric Olefination Reactions; Development and Application to Natural Product Synthesis
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis deals with the development and application of methods for asymmetric olefinations, in particular Horner-Wadsworth-Emmons (HWE) reactions, in the synthesis of certain natural products.

Relying on asymmetric HWE reactions to access key building blocks, two natu-ral products, pyranicin and pyragonicin, were synthesized from common late intermediates. The utility of the HWE reactions is highlighted through a desymmetrization of a meso-dialdehyde as well as a stereoconvergent reaction sequence employing the sequential use of a HWE parallel kinetic resolution fol-lowed by a Pd-catalyzed allylic substitution to convergently transform a race-mate to a single stereoisomer of the product. Methodological extensions of these syntheses include a divergent synthesis of 2,3,6-substituted tetrahydropyran derivatives and application of Zn-mediated asymmetric alkynylations to install key stereocenters.

Synthetic studies directed towards a more complex target, mucocin, employing a triply convergent strategy, have also been performed. Expedient and reliable routes to three key fragments were developed, as well as methodology to access to all nine stereocenters. The fragment coupling to assemble the oligonuclear core still remains a challenge, however. Key features of the synthesis include the formation of two fragments from a common precursor derived from an asymmetric HWE desymmetrization, Zn-mediatedated asymmetric alkynylations, a stereoselective oxa-Michael cyclization dependent on a simultaneous protective group migration and a one-pot procedure for the synthesis of a TBS protected iodohydrin from a terminal epoxide.

An investigation of the possibilities for developing a transition metal catalyzed asymmetric olefination using a chiral Re-complex is outlined. An enantioen-riched BINAP-Re complex was synthesized and characterized by X-ray. An efficient protocol for the olefination of functionalized aldehydes employing this catalyst was developed, but gave racemic products in two attempted kinetic resolutions of racemic substrates, most likely due to a reaction pathway proceeding via a non-metal associated phosphonium ylide.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Series
Trita-IOK, ISSN 1100-7974 ; 2006:103
Keyword
Antitumor agents, Asymmetric Horner-Wadsworth-Emmons, Desymmetrization, Metal-catalyzed olefination, Mucocin, Palladium-catalyzed allylic substitution, Parallel kinetic resolution, Pyranicin, Pyragonicin, Rhenium, Stereoconvergent synthesis, Stereodivergent synthesis, Stereoselective synthesis, Tetrahydropyran, Wittig reaction
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-4088 (URN)91-7178-427-6 (ISBN)
Public defence
2006-09-20, F3, Lindstetsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100921Available from: 2006-08-28 Created: 2006-08-28 Last updated: 2010-09-21Bibliographically approved

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