613672-33-6Relevant academic research and scientific papers
BETA-AMINO ACIDS AND METHODS AND INTERMEDIATES FOR MAKING SAME
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Page/Page column 13-14, (2011/10/02)
Disclosed are β-amino acids that are unsubstituted in the β position; that are substituted in the β position with an aryl group; that are substituted in the α position with an aryl group; that bear two substituents in the α position; and/or that are substituted in the α and β positions with groups which, together with the carbon atoms at the α and β positions, form a ring. Also disclosed are methods for making the above-mentioned β-amino acids and other β-amino acids which involve providing an α,β-unsaturated imide; converting the α,β-unsaturated imide to a 2-substituted-isoxazolidin-5-one; and converting the 2-substituted-isoxazolidin-5-one to a β-amino acid.
Elucidating the mechanism of the asymmetric aza-Michael reaction
Phua, Pim Huat,Mathew, Suju P.,White, Andrew J. P.,De Vries, Johannes G.,Blackmond, Donna G.,Hii, King Kuok
, p. 4602 - 4613 (2008/02/09)
The mechanism of the palladium-catalysed asymmetric aza-Michael addition of aniline to α,β-unsaturated N-imide was examined from several aspects using a combination of techniques, including X-ray crystallography, mass spectrometry, NMR, UV/Vis spectroscopy, and kinetic studies. The binding of aniline to the dicationic palladium(II) metal centre was found to occur in two consecutive steps: The binding of the first aniline is fast and reversible, whereas the binding of the second aniline is slower and irreversible. This occurs in competition with the binding of the N-imide, which forms a planar six-membered chelate ring with the metal centre; coordinating through the 1,3-dicarbonyl moiety. Isotopic labelling revealed that the addition of N-H occurs in a highly stereoselective manner, allowing the synthesis of optically active β2- and β2.3-amino acid derivatives. The stereochemistry of the addition is postulated to be syn. In situ kinetic studies provided evidence for product inhibition. The binding of the N-imide to the catalyst was found to be the rate-limiting step. Aniline was found to be an inhibitor of the pre-catalyst. The study culminated in the design of a new reaction protocol. By maintaining a low concentration of the aniline substrate during the course of the reaction, significant enhancement of yield and enantioselectivity can be achieved.
Enantioselective cycloadditions with α,β-disubstituted acrylimides
Sibi, Mukund P.,Ma, Zhihua,Itoh, Kennosuke,Prabagaran, Narayanasamy,Jasperse, Craig P.
, p. 2349 - 2352 (2007/10/03)
(Chemical Equation Presented) The use of N-H imide templates provides a solution to the problem of rotamer control in Lewis acid catalyzed reactions of α,β-disubstituted acryloyl imides. Reactions proceed through the s-cis rotamer and with improved reactivity because A1,3 strain is avoided. Enantioselective nitrone, nitrile oxide, and Diels-Alder cycloadditions demonstrate the principle.
Enantioselective radical addition/trapping reactions with α,β-disubstituted unsaturated imides. Synthesis of anti-propionate aldols
Sibi, Mukund P.,Petrovic, Goran,Zimmerman, Jake
, p. 2390 - 2391 (2007/10/03)
This manuscript describes a highly diastereo- and enantioselective intermolecular radical addition/hydrogen atom transfer to α,β-disubstituted enoates. Additionally, we show that anti-propionate aldol-like products can be easily prepared from α-methyl-β-acyloxyenoates in good yields and high diastereo- and enantioselectivities. Copyright
Enantioselective synthesis of α,β-disubstituted-β-amino acids
Sibi, Mukund P.,Prabagaran, Narayanasamy,Ghorpade, Sandeep G.,Jasperse, Craig P.
, p. 11796 - 11797 (2007/10/03)
Highly diastereoselective and enantioselective addition of N-benzylhydroxylamine to imides 17 and 20-30 produces α,β-trans-disubstituted N-benzylisoxazolidinones 19 and 31-41. These reactions proceed in 60-96% ee with 93-99% de's using 5 mol % of Mg(NTf2)2 and ligand 18. The product isoxazolidinones can be hydrogenolyzed directly to provide ∞,β-disubstituted-β-amino acids. Copyright
