- A practical approach to the resolution of racemic N-benzyl α-amino acids by liquid-liquid extraction with a lipophilic chiral salen-cobalt(III) complex
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(Chemical Equation Presented) Liquidating the assets: Coordination of one enantiomer from a racemic mixture of N-benzyl α-amino acids (N-Bn-AA) to the lipophilic chiral [CoIII(salen)(OAc)] complex results in its extraction into the organic phas
- Reeve, Toby B.,Cros, Jean-Philippe,Gennari, Cesare,Piarulli, Umberto,De Vries, Johannes G.
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p. 2449 - 2453
(2007/10/03)
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- The first highly enantioselective homogeneously catalyzed asymmetric reductive amination: Synthesis of α-N-benzylamino acids
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High-throughput screening considering a library of 96 chiral P-ligands involved in two types of RhI complexes was used for the identification of homogeneous catalysts for the highly enantioselective reductive amination of α-keto acids with benzylamine. After optimization of the reaction conditions and scale-up with a cationic Rh-Deguphos catalyst, a range of chiral α-amino acids could be produced by this new reaction in good yield and by up to 98% ee.
- Kadyrov, Renat,Riermeier, Thomas H.,Dingerdissen, Uwe,Tararov, Vitali,Boerner, Armin
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p. 4067 - 4070
(2007/10/03)
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- Syntheses of optically active α-amino nitrites by asymmetric transformation of the second kind using a principle of O. Dimroth
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A mixture of solids As and Bs in equilibrium with the dissolved compounds A1 and B1 is transformed completely into one pure solid, say Bs, if the dissolved compounds A1?B1 are equilibrating in solution. This is applied to transform 1:1 mixtures of solid diastereomeric amygdalates (2-hydroxy-2-phenylacetates; mandelates) (R,R)-3 + (S,R)-3 prepared from racemic α-amino nitriles (R,S)-1 with (R)-mandelic acid 2 into stereochemically pure single diastereomers (R,R)-3, or (S,R)-3 (de > 97%) ('asymmetric transformation of the second kind by application of Dimroth's principle'). Decomposition of the amygdalates (R,R)-3, or (S,R)-3, with aqueous base affords the enantiomerically pure α-amino nitriles (A)-1, or (S)-1 (ten examples). The chiral auxiliary (R)-mandelic acid is recovered almost quantitatively. The optically active α-amino nitriles are hydrolyzed to amides 6, and further to α-N-alkylamino acids 7. N-Benzylamino acids 7 are hydrogenated to α-amino acids 8. Some of the optically active α-amino nitriles 1 are reduced to optically active 1,2-diamines 9. In most cases, absolute configurations could be assigned by comparison of the specific rotations observed with those of authentic compounds.
- Hassan, Nasser A.,Bayer, Erwin,Jochims, Johannes C.
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p. 3747 - 3757
(2007/10/03)
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