- α-Methyl phenylglycines by asymmetric α-arylation of alanine and their effect on the conformational preference of helical Aib foldamers
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α-Arylated alanine derivatives were made enantioselectively by migratory rearrangement of a urea derivative using (R,R)-pseudoephedrine as a chiral auxiliary. Incorporation of a single residue of the product α-methyl phenylglycine into an otherwise achiral oligomer of aminoisobutyric acid oligomer induced a preferred screw sense, detectable by a NMR reporter located at the remote terminus of the oligomer. The magnitude of the screw sense induction was greater when the chiral residue was located at the N-terminus of the foldamer, and in some cases the sense of induction was opposite to that of related α-methylated amino acids with α-substituents other than aryl.
- Costil, Romain,Fernández-Nieto, Fernando,Atkinson, Rachel C.,Clayden, Jonathan
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supporting information
p. 2757 - 2761
(2018/04/27)
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- Pseudoephedrine-Directed Asymmetric α-Arylation of α-Amino Acid Derivatives
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Available α-amino acids undergo arylation at their α position in an enantioselective manner on treatment with base of N′-aryl urea derivatives ligated to pseudoephedrine as a chiral auxiliary. In situ silylation and enolization induces diastereoselective migration of the N′-aryl group to the α position of the amino acid, followed by ring closure to a hydantoin with concomitant explulsion of the recyclable auxiliary. The hydrolysis of the hydantoin products provides derivatives of quaternary amino acids. The arylation avoids the use of heavy-metal additives, and is successful with a range of amino acids and with aryl rings of varying electronic character.
- Atkinson, Rachel C.,Fernández-Nieto, Fernando,Mas Rosell?, Josep,Clayden, Jonathan
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p. 8961 - 8965
(2015/08/03)
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- Enantioselective Synthesis of α-Quaternary Amino Acids by Alkylation of Deprotonated α-Aminonitriles
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A series of α-quaternary arylglycines were prepared in high optical purity (up to 98% ee) by α-alkylation of deprotonated α-aminonitriles derived by the Strecker reaction from (4S,5S)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane. The procedure includes only chromatographic purification of the final products and is devoid of chromatography or crystallization operations on intermediates to raise the optical purity.
- Netz, Isabelle,Kucukdisli, Murat,Opatz, Till
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p. 6864 - 6869
(2015/10/06)
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- Nitrilases
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The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition, methods of designing new nitrilases and methods of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
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Paragraph 0263-0264
(2015/09/22)
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- Nitrilases, nucleic acids encoding them and methods for making and using them
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The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition methods of designing new nitrilases and method of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
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Page/Page column 52
(2016/01/09)
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- Bifunctional iminophosphorane organocatalysts for enantioselective synthesis: Application to the ketimine nitro-Mannich reaction
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The design, synthesis, and development of a new class of modular, strongly basic, and tunable bifunctional Bronsted base/H-bond-donor organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane as the Bronsted basic moiety and are readily synthesized via a last step Staudinger reaction of a chiral organoazide and a triarylphosphine. Their application to the first general enantioselective organocatalytic nitro-Mannich reaction of nitromethane to unactivated ketone-derived imines allows the enantioselective construction of β-nitroamines possessing a fully substituted carbon atom. The reaction is amenable to multigram scale-up, and the products are useful for the synthesis of enantiopure 1,2-diamine and α-amino acid derivatives.
- Nunez, Marta G.,Farley, Alistair J. M.,Dixon, Darren J.
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p. 16348 - 16351
(2013/12/04)
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- Mitsunobu approach to the synthesis of optically active α,α-disubstituted amino acids
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Chiral tertiary α-hydroxy esters of known stereochemical configuration were transformed to α-azido esters by Mitsunobu reaction with HN3. Optimization of this reaction was shown to proceed at room temperature with high chemical yield using 1,1-(azodicarbonyl)dipiperidine (ADDP) and trimethylphosphine (PMe3). Complete inversion of configuration was observed at the α-carbon. Several α,α- disubstituted amino acids were synthesized in high overall chemical yield and optical purity.
- Green, Jonathan E.,Bender, David M.,Jackson, Stona,O'donnell, Martin J.,Mccarthy, James R.
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supporting information; experimental part
p. 807 - 810
(2009/08/08)
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- The proline-catalyzed asymmetric amination of branched aldehydes
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An efficient access to configurationally stable α,β- disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding α-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free α-alkylated phenylglycine derivative. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Baumann, Thomas,Vogt, Henning,Braese, Stefan
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p. 266 - 282
(2007/10/03)
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- Synthesis of optically active α-methylamino acids and amides through biocatalytic kinetic resolution of amides
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Catalyzed by Rhodococcus sp. AJ270, a nitrile hydratase and amidase containing microbial whole-cell catalyst, under very mild conditions, a number of racemic α-methylamino amides were resolved into the corresponding optically active (S)-(+)-α-methylamino acids and (R)-(-)-α- methylamino amides. The steric requirement of the amidase against α-amino phenylacetamides bearing methyl group(s) at α-amino nitrogen and/or α-carbon was also studied. Coupled with the chemical hydrolysis of amide, the biotransformation process provided a direct synthesis of α-methylamino acids in both enantiomeric forms from readily available racemic amides.
- Wang, Mei-Xiang,Liu, Jun,Wang, De-Xian,Zheng, Qi-Yu
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p. 2409 - 2416
(2007/10/03)
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- Efficient biocatalytic synthesis of highly enantiopure α-alkylated arylglycines and amides
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A number of racemic α-alkylarylglycine amides including 1-amino-1-carbamoyl-1,2,3,4-tetrahydronaphthalene underwent efficient biocatalytic hydrolysis under very mild conditions to afford the corresponding (S)-α-alkylarylglycines and (R)-α-alkylarylglycine
- Wang, Mei-Xiang,Lin, Shuan-Jun,Liu, Jun,Zheng, Qi-Yu
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p. 439 - 445
(2007/10/03)
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- Stereospecific construction of chiral quaternary carbon compounds from chiral secondary alcohol derivatives
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Chiral tertiary dichloromethylcarbinol derivatives, prepared by stereospecific α C-H insertion reaction of dichlorocarbene with protected chiral secondary alcohols, were converted into intermediary α-chloroepoxides which gave stereospecifically chiral qua
- Masaki, Yukio,Arasaki, Hideki,Iwata, Masashi
-
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- Enantioselective catalytic addition of HCN to ketoimines. Catalytic synthesis of quaternary amino acids.
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[formula: see text] Highly enantioselective addition of HCN to ketoimines has been achieved for the first time using readily accessible and recyclable Schiff base catalysts. Essentially quantitative isolated yield and enantioselectivity of up to 95% ee wa
- Vachal,Jacobsen
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p. 867 - 870
(2007/10/03)
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- Applications of the sulfinimine-mediated asymmetric strecker synthesis to the synthesis of α-alkyl α-amino acids
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Addition of Et2AlCN and i-PrOH to ketosulfinimines (N-sulfinyl imines) affords corresponding α-alkyl α-amino nitriles in moderate to good yields. The diastereoselectivity is largely dependent on the E/Z isomer ratio of the ketosulfinimine. Hydrolysis of the diastereomerically pure amino nitriles affords enantiopure α-alkyl α-amino acids in moderate to good yields.
- Davis,Lee,Zhang,Fanelli
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p. 8704 - 8708
(2007/10/03)
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- α-Hydroxymethylphenylglycine and α-hydroxymethylphenylalanine: Synthesis, resolution, and absolute configuration
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Racemic α-hydroxymethylphenylglycine and α-hydroxymethylphenylalanine have been synthesized by selective hydroxymethylation of oxazolones derived from phenylglycine and phenylalanine, and resolved into enantiomers by fractional crystallization of their di
- Olma
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p. 1442 - 1447
(2007/10/03)
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- L-phenylalanine cyclohexylamide: A simple and convenient auxiliary for the synthesis of optically pure α,α-disubstituted (R)- and (S)-amino acids
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This work describes L-phenylalanine cyclohexylamide (5c) as a simple, cheap, and powerful chiral auxiliary for the synthesis of a series of optically pure α,α-disubstituted (R)- and (S)-amino acids of type 1, such as (R)- and (S)-2-methyl-phenylalanine (1a), (R)- and (S)-2-methyl-2-phenylglycine (1b), and (R)- and (S)-2-methylvaline (1c). These amino acids were efficiently transformed into the suitably protected and activated amino-acid building blocks (R)- and (S)-12b and (R)- and (S)-12c which are ready for incorporation into peptides by solution or solid-phase techniques. Based on the crystal structures of 6b, 6c, and 7a belonging to the diastereoisomeric peptides series 6 and 7, the absolute configurations of each member of the series were determined. β-Turn geometries of type II' and I were observed for 6b and 7a, respectively, whereas 6c crystallized in an extended conformation. The impacts of side-chain variation on conformation and crystal packing of these triamides are discussed.
- Obrecht,Bohdal,Broger,Bur,Lehmann,Ruffieux,Schonholzer,Spiegler,Muller
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p. 563 - 580
(2007/10/02)
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- SINTESIS ASIMETRICA DE α-FENILAMINOACIDOS
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A new synthetic strategy to obtain α-phenylamino acids in enantiomerically pure form is described.The new route is based on the highly diastereoselective alkylation of (1S,2R,4R)-10-dicyclohexylsulfamoylisobornyl 2-phenylcyanoacetate and subsequent Curtiu
- Cativiela, Carlos,Villegas, Maria D. Diaz de,Galvez, Jose A.,Lapena, Yolanda
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p. 432 - 437
(2007/10/02)
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- Enzymatic resolution of α,α-disubstituted α-amino acid esters and amides
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The scope and limitations of the enzymatic resolution of α,α-disubstituted α-amino acid amides by an amino acid amidase from Mycobacterium neoaurum and of the corresponding ethyl esters with Pig liver esterase (PLE) have been studied. Moderate enantiomeric excesses were obtained with PLE, with only a narrow substrate specificity. Mycobacterium neoaurum on the contrary yields a broad range of S-α,α-disubstituted α-amino acids 1 and the corresponding R-amides 2.
- Kaptein,Boesten,Broxterman,Peters,Schoemaker,Kamphuis
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p. 1113 - 1116
(2007/10/02)
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- Synthese enantioselective d'α-aryl amino acides: subtitution nucleophile aromatique sur le fluorobenzene chrome tricarbonyle d'enolates chiraux
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We report here a convenient synthesis of optically pure α-aryl amino acids by enantioselective substitution of fluorobenzene tricarbonylchromium using the Schiff bases of L-alanine methyl ester with (1R,2R,5R)-2-hydroxy-3-pinanone in presence of LDA or deprotonated 2-(tert-butyl)-4-methyl-1,3-oxazolidin-5 one.
- Chaari, M.,Jenhi, A.,Lavergne, J.-P.,Viallefont, Ph.
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p. C10 - C13
(2007/10/02)
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- REACTIONS OF FLUOROBENZENE TRICARBONYLCHROMIUM COMPLEXES WITH ANIONS FROM SCHIFF BASES OF α-AMINO ESTERS; ENANTIOSELECTIVE SYNTHESIS OF α-ARYL AMINO ACIDS
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We report here a convenient synthesis of α-substituted aryl amino acids via the addition of α-imino esters to fluorobenzene tricarbonylchromium complexes.Optically pure α-aryl amino acids have been prepared by enantioselective substitution of fluorobenzene complexes using Schiff bases of L-alanine, leucine and valine methyl esters and (1R,2R,5R)-2-hydroxypinan-3-one.
- Chaari, Mohamed,Jenhi, Aicha,Lavergne, Jean-Pierre,Viallefont, Philippe
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p. 4619 - 4630
(2007/10/02)
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- Synthesis of Optically Pure α-Alkylated α-Amino Acids and a Single-Step Method for Enatiomeric Excess Determination
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A method for the enzymatic resolution of the amides of some racemic α-alkylated amino acids is described as well as a method involving derivatization with (S)-2-chloropropionyl chloride followed by 1H NMR analysis to establish the enantiomeric excesses of the free amino acids.
- Kruizinga, Wim H.,Bolster, John,Kellogg, Richard M.,Kamphuis, Johan,Boesten, Wilhelmus H. J.,et al.
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p. 1826 - 1827
(2007/10/02)
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