- An improved synthesis of optically pure 4-Boc-5,6-diphenylmorpholin-2-one and 4-Cbz-5,6-diphenylmorpholin-2-one
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A convenient synthesis of optically pure 4-Boc-5,6-diphenylmorpholin-2-one and 4-Cbz-5,6-diphenylmorpholin-2-one by reaction of (+)- or (-)-2-amino-1,2-diphenylethanol with ethyl bromoacetate, followed by N-protection, and p-TsOH-mediated ring-closure is
- Dastlik, Kim A.,Sundermeier, Uta,Johns, Deidre M.,Chen, Yuyin,Williams, Robert M.
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p. 693 - 696
(2007/10/03)
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- Chiral Synthesis of L-γ-Carboxylgutamic Acid (L-Gla)
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A two step synthesis involving the use of a chiral template, benzyl (2R,3S)-(-)-6-oxo-2,3-diphenyl-4-morpholine-carboxylate (5a), provides orthogonally protected L-Gla (9) in 60percent overall yield (>99percent ee), with no resolution required.
- Schuerman, Marla A.,Keverline, Kathryn I.,Hiskey, Richard G.
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p. 825 - 828
(2007/10/02)
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- Practical Asymmetric Syntheses of α-Amino Acids through Carbon-Carbon Bond Constructions on Electrophilic Glycine Templates
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The optically active D- and L-erythro-4-(benzyloxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-ones (3) and D- and L-erythro-4-(tert-butoxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-ones (3) can be efficiently brominated to serve as electrophilic glycine templates for the asymmetric synthesis of amino acids.It was found that coupling to these templates can proceed with either net retention or net inversion of stereochemistry.The final deblocking to the amino acids is accomplished with either dissolving-metal reduction or catalytic hydrogenolysis.The syntheses of β-ethyl aspartic acid, norvaline, allylglycine, alanine, norleucine, homophenylalanine, p-methoxyhomophenylalanine, cyclopentylglycine, and cyclopentenylglycine and a formal synthesis of clavalanine are described.In addition, the direct asymmetric syntheses of N-t-BOC-allylglycine and N-t-BOC-cyclopentenylglycine are described.
- Williams, Robert M.,Sinclair, Peter J.,Zhai, Dongguan,Chen, Daimo
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p. 1547 - 1557
(2007/10/02)
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