- Stereoselective synthesis of allylic amines by rearrangement of allylic trifluoroacetimidates: Stereoselective synthesis of polyoxamic acid and derivatives of other α-amino acids
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On heating in xylene under reflux, allylic trifluoroacetimidates undergo [3,3] sigmatropic rearrangement to regioisomeric allylic trifluoroacetamides. Examples include the rearrangements of the trifluoroacetimidates 16 and 73 to the trifluoroacetamides 17 and 74, which were incorporated into stereoselective syntheses of polyoxamic acid 1, and the rearrangement of the trifluoroacetimidate 26. The rearrangement was the key step in asymmetric syntheses of the (S)- and (R)-valine derivatives 37 and 48. Other examples include rearrangements of the trifluoroacetimidates 52, 54 and 56 prepared from geraniol, cinnamyl alcohol and sorbyl alcohol, respectively, and the more complex trifluoroacetimidates 62 and 69. The stereoselectivity of these rearrangements, which are somewhat faster than rearrangements of analogous allylic trichloroacetimidates, is consistent with the participation of chair-like, six-membered, transition structures. The Royal Society of Chemistry 1999.
- Savage, Ian,Thomas, Eric J.,Wilson, Peter D.
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p. 3291 - 3303
(2007/10/03)
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- Expeditious synthesis of Mosher amides using a solid supported carbodiimide
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A novel method of Mosher amide synthesis using a solid supported carbodiimide in CDCl3 is described. Estimation of optical purity can be promptly achieved by direct NMR analysis of the reaction solvent.
- Adamczyk, Maciej,Fishpaugh, Jeffrey R.
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p. 7171 - 7172
(2007/10/03)
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- Elucidation of the absolute configurations of amino acids and amines by the modified mosher's method
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Application of the modified Mosher's method to the N-MTPA derivatives of several amino acid esters and acyclic amines indicates that this method may be generally used to determine the absolute configurations of the α-carbons of amino compounds of less tha
- Kusumi, Takenori,Fukushima, Toshiro,Ohtani, Ikuko,Kakisawa, Hiroshi
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p. 2939 - 2942
(2007/10/02)
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- The Asymmetric Synthesis of α-Amino and α-Hydrazino Acid Derivatives via The Stereoselective Amination of Chiral Enolates with Azodicarboxylate Esters.
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The utility of azodicarboxylate esters as (+)NH2 and (+)NH-NH2 synthons in highly diastereoselective reactions with chiral carboximide-derived enolates has been demonstrated.The lithium enolates derived from 4-substituted N-acyl 2-oxazolidinones were found to react with di-tert-butyl azodicarboxylate (DBAD) to afford the derived 2-hydrazido carboxylic acid derivetives in yields in excess of 90 percent.The diastereoselectivities of these reactions ranged from 97percent to greater than 99percent.The subsequent transformation of these adducts to both α-hydrazino and α-amino acids in enantiomeric purities in excess of 99percent is described.
- Evans, David A.,Britton, Thomas C.,Dorow, Roberta L.,Dellaria, Joseph F.
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p. 5525 - 5540
(2007/10/02)
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