- Enantioselective hydrocyanation of N-protected aldimines
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Enantioselective hydrocyanation of N-benzyloxycarbonyl aldimines catalyzed by a Ru[(S)-phgly]2[(S)-binap]/C6H5OLi system or a bimetallic complex [Li{Ru[(S)-phgly]2[(S)-binap]}]Cl affords the amino nitriles in 92 - 99% ee. The reaction is carried out in tert-C 4H9OCH3 with a substrate-to-catalyst molar ratio in the range of 500 - 5000 at -20 to 0°C. Primary, secondary, and tertiary alkyl imines as well as the aryl and heteroaryl substrates are smoothly cyanated to produce the desired products in high yield.
- Uemura, Masato,Kurono, Nobuhito,Ohkuma, Takeshi
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supporting information; experimental part
p. 882 - 885
(2012/04/05)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 61
(2010/12/31)
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- One-pot, regioselective synthesis of substituted arylglycines for kinetic resolution by penicillin G acylase
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Amido-alkylation of electron-rich arenes with phenylacetamide and glyoxylic acid offers an in-expensive route to a large variety of N-phenylacetylated arylglycines that are suited for immediate enzymatic resolution by penicillin G acylase. When performed under mild conditions at 5 °C in acetic acid/HCl, this simple one-pot operation resulted in the formation of single regioisomers only (≥98%). Subsequent kinetic resolution of the amino acid derivatives by penicillin G acylase at pH 8.0 occurred generally with E values >100 and thus furnished free (S)-configurated arylglycines with high enantiomeric purity. The corresponding enantiopure (R)-substrates, easily separable by a phase-selective extraction process, provided the corresponding (R)-enantiomers upon conventional hydrolysis. This one-pot, two-step procedure for arylglycine synthesis, resolution and work-up requires a minimum of equipment and grants rapid access to both enantiopure (S)- and (R)-antipodes of non-natural α-amino acids in small-to large-scale quantities.
- Grundmann, Peter,Fessner, Wolf-Dieter
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experimental part
p. 1729 - 1735
(2009/07/24)
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- New hydantoinases from thermophilic microorganisms - Synthesis of enantiomerically pure D-amino acids
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A series of 14 D-α-amino acids were prepared in high chemical and optical yields from the corresponding racemic hydantoins by employing two novel hydantoinases from thermophilic microorganisms.
- Keil,Schneider,Rasor
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p. 1257 - 1260
(2007/10/02)
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- An Efficient and Practical Synthesis of L-α-Amino Acids Using (R)-Phenylglycinol as a Chiral Auxiliary
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L-α-Amino acids including L-α-arylglycines were conveniently and stereoselectively synthesized via the α-amino carbonitriles given by the Strecker reaction of (R)-2-amino-2-phenylethanol with aldehydes and hydrogen cyanide.The stereoselectivity of these α-amino carbonitriles was thermodynamically controlled.
- Inaba, Takashi,Kozono, Ichiro,Fujita, Makoto,Ogura, Katsuyuki
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p. 2359 - 2365
(2007/10/02)
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- Stereoselective synthesis of L-amino acids via Strecker and Ugi reactions on carbohydrate templates
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L-Amino acid derivatives are stereoselectively synthesized in high yield using 2,3,4-tri-O-pivaloyl-α-D-arabinopyranosylamine or 2,3,4-tri-O-pivaloyl-β-L-fucopyranosylamine as the chiral auxiliary in Strecker and Ugi reactions.
- Kunz,Pfrengle,Ruck,Sager
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p. 1039 - 1042
(2007/10/02)
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- Nonproteinogenic Amino Acids, III. - Syntheses of the Enantiomerically Pure 2-(2-Thienyl)- and 2-(3-Thienyl)glycines. - Molecular Structure of the Intermediate Schiff's Bases
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The syntheses of enantiomerically pure D-(-)- and L-(+)-2-(2-thienyl)- and 2-(3-thienyl)glycines (6a-d) are described.Preparing the amino nitriles 4 directly from 2-thiophenecarbaldehyde (1a) or 3-thiophenecarbaldehyde (1b), respectively, and (4S,5S)-(+)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane (2), and hydrocyanic acid (one-step procedure), the aminonitriles 4a and 4b, respectively, are formed in excess.By crystallization they are obtained diastereomerically pure leading to enantiomerically pure D-amino acids 6a and 6b.If, however, the intermediate Schiff's bases 3 are isolated as crystals and then converted with hydrocyanic acid into the respective aminonitriles 4 (two-step procedure), the diastereomeric aminonitriles 4c and 4d, respectively, crystallize resulting in enantiomerically pure L-amino acids 6a and 6d.X-ray structure analyses of the Schiff's bases 3c and 3e revealed the previously postulated E-configuration of the C=N bond and its chiral shielding by the phenyl substituent at C4.
- Weinges, Klaus,Brachmann, Helga,Stahnecker, Peter,Rodewald, Hans,Nixdorf, Matthias,Irngartinger, Hermann
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p. 566 - 578
(2007/10/02)
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