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  1. Article: Synthesis and application of P-stereogenic phosphines as superior reagents in the asymmetric aza-Wittig reaction.

    Headley, Catherine E / Marsden, Stephen P

    The Journal of organic chemistry

    2007  Volume 72, Issue 19, Page(s) 7185–7189

    Abstract: A wide variety of P-stereogenic aryldialkylphosphines were prepared in enantioenriched form by a systematic diversification of the (-)-sparteine-mediated dynamic kinetic resolution of racemic lithiophosphine-boranes reported by Livinghouse. Excellent ... ...

    Abstract A wide variety of P-stereogenic aryldialkylphosphines were prepared in enantioenriched form by a systematic diversification of the (-)-sparteine-mediated dynamic kinetic resolution of racemic lithiophosphine-boranes reported by Livinghouse. Excellent asymmetric induction was observed provided that the intermediate lithiophosphine/sparteine complex precipitated from solution; more soluble derivatives returned poor ee's or racemic material. The resulting phosphine-boranes were deprotected and used as reagents in the desymmetrizing asymmetric aza-Wittig reaction of 2-alkyl-2-(3-azidopropyl)cyclohexane-1,3-diones, delivering the highest ee's yet observed in this process (up to 84% ee). Phosphines bearing bulky substituents required heating for the aza-Wittig reaction to proceed to completion, which 31P NMR studies showed to be due to interception of the reaction by the formation of unreactive (E)-phosphazides. This was circumvented by use of methyltrioxorhenium to catalyze the formation of iminophosphoranes from the azide and phosphine, allowing reactions to take place at ambient temperature, although the ee's of the asymmetric reactions were reduced in these examples.
    Language English
    Publishing date 2007-09-14
    Publishing country United States
    Document type Journal Article
    ZDB-ID 123490-0
    ISSN 1520-6904 ; 0022-3263
    ISSN (online) 1520-6904
    ISSN 0022-3263
    DOI 10.1021/jo0709908
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Flexibility in the partial reduction of 2,5-disubstituted pyrroles: application to the synthesis of DMDP.

    Donohoe, Timothy J / Headley, Catherine E / Cousins, Rick P C / Cowley, Andrew

    Organic letters

    2003  Volume 5, Issue 7, Page(s) 999–1002

    Abstract: reaction: see text] The partial reduction of electron-deficient 2,5-disubstituted pyrroles has been developed into a flexible procedure that gives control of relative stereochemistry by variation of the reduction conditions. After the reaction, the ... ...

    Abstract [reaction: see text] The partial reduction of electron-deficient 2,5-disubstituted pyrroles has been developed into a flexible procedure that gives control of relative stereochemistry by variation of the reduction conditions. After the reaction, the pyrroline products were dihydroxylated at C-3,4 to give either the cis or trans isomers; this flexibility means that a variety of polyhydroxylated pyrrolidines can be prepared in a short sequence. Finally, this method was applied to a synthesis of the naturally occurring glycosidase inhibitor DMDP.
    MeSH term(s) Alkaloids/chemical synthesis ; Alkaloids/chemistry ; Enzyme Inhibitors/chemical synthesis ; Enzyme Inhibitors/chemistry ; Glycoside Hydrolases/antagonists & inhibitors ; Imino Furanoses ; Isomerism ; Mannitol/analogs & derivatives ; Molecular Structure ; Pyrroles/chemistry ; Pyrrolidines
    Chemical Substances Alkaloids ; Enzyme Inhibitors ; Imino Furanoses ; Pyrroles ; Pyrrolidines ; Mannitol (3OWL53L36A) ; 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine (59920-31-9) ; Glycoside Hydrolases (EC 3.2.1.-)
    Language English
    Publishing date 2003-04-03
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1523-7060
    ISSN 1523-7060
    DOI 10.1021/ol027504h
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Enantioselective partial reduction of 2,5-disubstituted pyrroles via a chiral protonation approach.

    Donohoe, Timothy J / Freestone, Graeme C / Headley, Catherine E / Rigby, Caroline L / Cousins, Rick P C / Bhalay, Gurdip

    Organic letters

    2004  Volume 6, Issue 18, Page(s) 3055–3058

    Abstract: reaction: see text] The partial reduction of 2,5-pyrrole diester 1 followed by enantioselective protonation in situ to furnish synthetically useful building blocks is described. An enantiomeric excess of up to 74% was achieved using (-)-ephedrine and ... ...

    Abstract [reaction: see text] The partial reduction of 2,5-pyrrole diester 1 followed by enantioselective protonation in situ to furnish synthetically useful building blocks is described. An enantiomeric excess of up to 74% was achieved using (-)-ephedrine and related analogues as chiral proton sources. The pyrroline product obtained could be recrystallized to give enantiomerically pure material.
    MeSH term(s) Catalysis ; Combinatorial Chemistry Techniques ; Ephedrine/chemistry ; Indicators and Reagents ; Molecular Structure ; Oxidation-Reduction ; Pyrroles/analysis ; Pyrroles/chemical synthesis ; Pyrroles/chemistry ; Stereoisomerism
    Chemical Substances Indicators and Reagents ; Pyrroles ; Ephedrine (GN83C131XS)
    Language English
    Publishing date 2004-09-02
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1523-7060
    ISSN 1523-7060
    DOI 10.1021/ol049014q
    Database MEDical Literature Analysis and Retrieval System OnLINE

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