- 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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- ASYMMETRIC SYNTHESIS OF α-AMINO ACIDS: COMPARISON OF ENOLATE VS. CATION FUNCTIONALIZATION OF N-BOC-5,6-DIPHENYL-2,3,5,6-TETRAHYDRO-4H-1,4-OXAZIN-2-ONES
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Enolate generation and subsequent alkylation of the chiral glycinates 1 and 2 occurs with a high degree of diastereoselectivity.Reduction of the homologation products (3 and 4) furnishes with high enantiomeric excess, the N-t-BOC, and free α-amino acid derivates 5 and 6, respectively.
- Williams, Robert M.,Im, Myeong-Nyeo
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p. 6075 - 6078
(2007/10/02)
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