- Enantioselective synthesis of α-alkenyl α-amino acids via N-H insertion reactions
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A new highly enantioselective route to α-alkenyl α-amino acid derivatives, which are important naturally occurring compounds with attractive bioactivity and synthetic utility, was developed using a N-H insertion reaction of vinyldiazoacetates and tert-butyl carbamate cooperatively catalyzed by achiral dirhodium(ii) carboxylates and chiral spiro phosphoric acids under mild, neutral conditions. This reaction has a broad substrate scope, a fast reaction rate (turnover frequency > 6000 h-1), a high yield (61-99%), and excellent enantioselectivity (83-98% ee). The chiral spiro phosphoric acid, which is proposed to realize the enantioselectivity of the insertion reaction by promoting the proton transfer of a ylide intermediate by acting as a chiral proton shuttle catalyst, can suppress several usual side reactions of vinyldiazoacetates and broaden the applications of these versatile carbene precursors in organic synthesis. To our knowledge, it is the first highly enantioselective carbene insertion reaction of vinyldiazoacetates with heteroatom-hydrogen bonds in which the heteroatom has lone-pair electrons.
- Guo, Jun-Xia,Zhou, Ting,Xu, Bin,Zhu, Shou-Fei,Zhou, Qi-Lin
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- A green and expedient synthesis of enantiopure diketopiperazines via enzymatic resolution of unnatural amino acids
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Dipeptides comprising a d-phenylglycyl moiety coupled to the l-enantiomer of 2-amino butyric acid, norvaline, norleucine, and homocysteine were successfully synthesized from d-phenylglycine amide and the racemate of the corresponding unnatural amino acid.
- Pereira, Pedro C.,Arends, Isabel W.C.E.,Sheldon, Roger A.
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- Stereodivergent addition of allylmetal reagents to imines derived from (R)2,3-Di-O-benzylglyceraldehyde by appropriate selection of metal and double stereodifferentiation
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The addition of allylmetal reagents to N-benzylimines derived from (R)-2,3-di-O-benzylglyceraldehyde has been achieved with high yields and diastereoselectivities. Homoallylamine 2a of syn configuration is obtained preferentially with allylmagnesium bromide, whereas homoallylamine 2a of anti configuration is obtained as the major reaction product with allyl-9-borabicyclo[3.3.1]nonane. Appropriate combinations of the allylmetal reagent and imines derived from (R)-2,3-di-O-benzylglyceraldehyde and (S)- or (R)-1-phenylethylamine afforded syn or anti homoallylamines with total stereocontrol through double stereodifferentiation processes. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Badorrey, Ramon,Cativiela, Carlos,Diaz-de-Villegas, Maria D.,Diez, Roberto,Galvez, Jose A.
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Read Online
- Highly selective synthesis of d-amino acids from readily available l-amino acids by a one-pot biocatalytic stereoinversion cascade
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d-Amino acids are key intermediates required for the synthesis of important pharmaceuticals. However, establishing a universal enzymatic method for the general synthesis of d-amino acids from cheap and readily available precursors with few by-products is challenging. In this study, we constructed and optimized a cascade enzymatic route involving l-amino acid deaminase and d-amino acid dehydrogenase for the biocatalytic stereoinversions of l-amino acids into d-amino acids. Using l-phenylalanine (l-Phe) as a model substrate, this artificial biocatalytic cascade stereoinversion route first deaminates l-Phe to phenylpyruvic acid (PPA) through catalysis involving recombinant Escherichia coli cells that express l-amino acid deaminase from Proteus mirabilis (PmLAAD), followed by stereoselective reductive amination with recombinant meso-diaminopimelate dehydrogenase from Symbiobacterium thermophilum (StDAPDH) to produce d-phenylalanine (d-Phe). By incorporating a formate dehydrogenase-based NADPH-recycling system, d-Phe was obtained in quantitative yield with an enantiomeric excess greater than 99%. In addition, the cascade reaction system was also used to stereoinvert a variety of aromatic and aliphatic l-amino acids to the corresponding d-amino acids by combining the PmLAAD whole-cell biocatalyst with the StDAPDH variant. Hence, this method represents a concise and efficient route for the asymmetric synthesis of d-amino acids from the corresponding l-amino acids.
- Zhang, Danping,Jing, Xiaoran,Zhang, Wenli,Nie, Yao,Xu, Yan
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p. 29927 - 29935
(2019/10/01)
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- One-Pot Preparation of d-Amino Acids Through Biocatalytic Deracemization Using Alanine Dehydrogenase and Ω-Transaminase
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d-Amino acids are pharmaceutically important building blocks, leading to a great deal of research efforts to develop cost-effective synthetic methods. Preparation of d-amino acids by deracemization has been conceptually attractive owing to facile synthesis of racemic amino acids by Strecker synthesis. Here, we demonstrated biocatalytic deracemization of aliphatic amino acids into d-enantiomers by running cascade reactions; (1) stereoinversion of l-amino acid to a d-form by amino acid dehydrogenase and ω-transaminase and (2) regeneration of NAD+ by NADH oxidase. Under the cascade reaction conditions containing 100?mM isopropylamine and 1?mM NAD+, complete deracemization of 100?mM dl-alanine was achieved after 24?h with 95% reaction yield of d-alanine (> 99% eeD, 52% isolation yield). Graphical Abstract: [Figure not available: see fulltext.].
- Han, Sang-Woo,Shin, Jong-Shik
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p. 3678 - 3684
(2018/10/20)
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- Structure-guided engineering of: Meso -diaminopimelate dehydrogenase for enantioselective reductive amination of sterically bulky 2-keto acids
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meso-Diaminopimelate dehydrogenase (DAPDH) and mutant enzymes are an excellent choice of biocatalysts for the conversion of 2-keto acids to the corresponding d-amino acids. However, their application in the enantioselective reductive amination of bulky 2-keto acids, such as phenylglyoxylic acid, 2-oxo-4-phenylbutyric acid, and indole-3-pyruvic acid, is still challenging. In this study, the structure-guided site-saturation mutagenesis of a Symbiobacterium thermophilum DAPDH (StDAPDH) gave rise to a double-site mutant W121L/H227I, which showed dramatically improved enzyme activities towards various 2-keto acids including these sterically bulky substrates. Several d-amino acids were prepared in optically pure form. The molecular docking of substrates into the active sites of wild-type and mutant W121L/H227I enzymes revealed that the substrate binding cavity of the mutant enzyme was reshaped to accommodate these bulky substrates, thus leading to higher enzyme activity. These results lay a foundation for further shaping the substrate binding pocket and manipulating the interactions between the substrate and binding sites to access highly active d-amino acid dehydrogenases for the preparation of synthetically challenging d-amino acids.
- Cheng, Xinkuan,Chen, Xi,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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p. 4994 - 5002
(2018/10/17)
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- Asymmetric Transamination of α-Keto Acids Catalyzed by Chiral Pyridoxamines
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A new type of novel chiral pyridoxamines 3a-g containing a side chain has been developed. The pyridoxamines displayed catalytic activity and promising enantioselectivity in biomimetic asymmetric transamination of α-keto acids, to give various α-amino acids in 47-90% yields with up to 87% ee's under very mild conditions. An interesting effect of the side chain on enantioselectivity was observed in the reaction.
- Lan, Xiaoyu,Tao, Chuangan,Liu, Xuliang,Zhang, Aina,Zhao, Baoguo
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supporting information
p. 3658 - 3661
(2016/08/16)
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- Deracemization of amino acids by coupling transaminases of opposite stereoselectivity
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Biocatalytic deracemization of amino acids without relying on oxidase-based deamination of an unwanted enantiomer was demonstrated by coupling a-and w-transaminases displaying opposite stereoselectivity. This strategy employs isopropylamine and a keto acid as cosubstrates and is free of generation of hydrogen peroxide which is troublesome in the conventional oxidase-based methods.
- Park, Eul-Soo,Shin, Jong-Shik
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p. 3505 - 3509
(2015/02/19)
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- Biocatalytic asymmetric synthesis of unnatural amino acids through the cascade transfer of amino groups from primary amines onto keto acids
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Flee to the hills: An unfavorable equilibrium in the amino group transfer between amino acids and keto acids catalyzed by α-transaminases was successfully overcome by coupling with a ω-transaminase reaction as an equilibrium shifter, leading to efficient asymmetric synthesis of diverse unnatural amino acids, including L-tert-leucine and D-phenylglycine. Copyright
- Park, Eul-Soo,Dong, Joo-Young,Shin, Jong-Shik
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p. 3538 - 3542
(2014/01/06)
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- Characterization of d-amino acid aminotransferase from Lactobacillus salivarius
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We searched a UniProt database of lactic acid bacteria in an effort to identify d-amino acid metabolizing enzymes other than alanine racemase. We found a d-amino acid aminotransferase (d-AAT) homologous gene (UniProt ID: Q1WRM6) in the genome of Lactobacillus salivarius. The gene was then expressed in Escherichia coli, and its product exhibited transaminase activity between d-alanine and α-ketoglutarate. This is the first characterization of a d-AAT from a lactic acid bacterium. L. salivarius d-AAT is a homodimer that uses pyridoxal-5′-phosphate (PLP) as a cofactor; it contains 0.91 molecules of PLP per subunit. Maximum activity was seen at a temperature of 60 °C and a pH of 6.0. However, the enzyme lost no activity when incubated for 30 min at 30 °C and pH 5.5 to 9.5, and retained half its activity when incubated at pH 4.5 or 11.0 under the same conditions. Double reciprocal plots of the initial velocity and d-alanine concentrations in the presence of several fixed concentrations of α-ketoglutarate gave a series of parallel lines, which is consistent with a Ping-Pong mechanism. The Km values for d-alanine and α-ketoglutarate were 1.05 and 3.78 mM, respectively. With this enzyme, d-allo-isoleucine exhibited greater relative activity than d-alanine as the amino donor, while α-ketobutylate, glyoxylate and indole-3-pyruvate were all more preferable amino acceptors than α-ketoglutarate. The substrate specificity of L. salivarius d-AAT thus differs greatly from those of the other d-AATs so far reported.
- Kobayashi, Jyumpei,Shimizu, Yasuhiro,Mutaguchi, Yuta,Doi, Katsumi,Ohshima, Toshihisa
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- SEPARATING AGENT FOR CHROMATOGRAPHY
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A separating agent for chromatography is provided that is useful for the separation of specific compounds, e.g., for the optical resolution of amino acids. This separating agent for chromatography provides a higher productivity and contains a crown ether-like cyclic structure and optically active binaphthyl. This separating agent for chromatography containing a crown ether-like cyclic structure and optically active binaphthyl is provided by introducing a substitution group for binding to carrier into a specific commercially available 1,1′-binaphthyl derivative that has substituents at the 2, 2′, 3, and 3′ positions, then introducing a crown ether-like cyclic structure, and subsequently chemically bonding the binaphthyl derivative to the carrier through the substitution group for binding to carrier.
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Paragraph 0074; 0075
(2013/08/15)
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- Astins K-P, six new chlorinated cyclopentapeptides from Aster tataricus
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During further investigation on the methanol extract of roots and rhizomes of Aster tataricus, six new chlorinated cyclopentapeptides, designated as astins K-P (9-14), together with eight known derivatives, astins A-H (1-8), were isolated. Structures of the new cyclopeptides were established using extensive spectroscopic methods, and the absolute configurations were determined by the advanced Marfey's method. Astin P (14) represents a unique cyclopentapeptide linking as cyclo-(l-Pro (Cl2)1-l-allo-Thr 2-l-Ser3-l-β-Phe4-l-Ava5). Astin B (2) showed cytotoxicity against BGC-823 cell with IC50 value of 19.2 μg/ml. Astin C (3) exhibited cytotoxicity on HCT-116 and BGC-823 cells with IC50 values of 13.4 and 3.3 μg/ml, respectively.
- Xu, Hui-Min,Zeng, Guang-Zhi,Zhou, Wen-Bing,He, Wen-Jun,Tan, Ning-Hua
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p. 7964 - 7969
(2013/08/23)
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- Chemical approach for interconversion of (S)- and (R)-α-amino acids
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Here we report a general method for the preparation of unnatural (R)-α-amino acids via complexation of α-(phenyl)ethylamine derived chiral reagent (S)-3 with various (S)-α-amino acids. The reactions proceed with synthetically useful chemical yields and thermodynamically controlled diastereoselectivity. Chiral reagent (S)-3 can be conveniently recovered and reused without any loss of enantiomeric purity and reactivity. The Royal Society of Chemistry 2013.
- Sorochinsky, Alexander E.,Ueki, Hisanori,Ace?a, José Luis,Ellis, Trevor K.,Moriwaki, Hiroki,Sato, Tatsunori,Soloshonok, Vadim A.
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p. 4503 - 4507
(2013/08/23)
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- Simplifying pyridoxal: Practical methods for amino acid dynamic kinetic resolution
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Figure presented Metal complexes of picolinaldehyde are identified as low-cost and environmentally benign catalysts, providing high reaction rates and turnovers for the racemization of amino acids. These pyridoxal surrogates demonstrate activity toward a variety of amino acid esters. Applications to chemoenzymatic dynamic kinetic resolutions provide access to amino acids in high yields and with excellent enantioselectivities, demonstrating their compatibility with protease-mediated transformations.
- Felten, Albert E.,Zhu, Gangguo,Aron, Zachary D.
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supporting information; experimental part
p. 1916 - 1919
(2010/07/06)
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- NOVEL IMIDAZOLIDINONE DERIVATIVE, METHOD OF PRODUCING THE SAME AND METHOD OF PRODUCING OPTICALLY ACTIVE AMINO ACID
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The objective of the present invention is to provide an optically active imidazolidinone derivative widely usable for synthesizing an optically active amino acid, a method of easily producing the derivative, and a method of easily producing an optically active amino acid by using the derivative. The objective can be achieved by producing an optically active amino acid using a novel optically active imidazolidinone derivative represented by a general formula (3) and the like. According to the method of the present invention, an optically active imidazolidinone derivative can be obtained by preferential crystallization from a mixture of isomers of the imidazolidinone derivative. Therefore, an optically active amino acid can be easily and stereoselectively produced without cumbersome procedures required for the conventional methods, such as resolution of diastereomers, synthesis from an optically active amino acid and resolution of isomers by silica gel column cromatography.
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Page/Page column 32-33
(2009/05/29)
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- Dynamic Kinetic resolution of α-amino acid esters in the presence of aldehydes
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A convenient procedure for the racemization of α-amino acid esters in the presence of catalytic amounts of salicylaldehydes is described. The combination of this racemization protocol with lipase-catalyzed ester hydrolysis allows successful dynamic kinetic resolution of various α-amino acid esters. The corresponding α-amino acids are obtained in high yield and optical purity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Schichl, Daniel A.,Enthaler, Stephan,Holla, Wolfgang,Riermeier, Thomas,Kragl, Udo,Beller, Matthias
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scheme or table
p. 3506 - 3512
(2009/04/07)
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- Creation of a broad-range and highly stereoselective D-amino acid dehydrogenase for the one-step synthesis of D-amino acids
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Using both rational and random mutagenesis, we have created the first known broad substrate range, nicotinamide cofactor dependent, and highly stereoselective D-amino acid dehydrogenase. This new enzyme is capable of producing D-amino acids via the reductive amination of the corresponding 2-keto acid with ammonia. This biocatalyst was the result of three rounds of mutagenesis and screening performed on the enzyme meso-diaminopimelate D-dehydrogenase. The first round targeted the active site of the wild-type enzyme and produced mutants that were no longer strictly dependent on the native substrate. The second and third rounds produced mutants that had an increased substrate range including straight-and branched-aliphatic amino acids and aromatic amino acids. The very high selectivity toward the D-enantiomer (95 to >99% ee) was shown to be preserved even after the addition of the five mutations found in the three rounds of mutagenesis and screening. This new enzyme could complement and improve upon current methods for D-amino acid synthesis.
- Vedha-Peters, Kavitha,Gunawardana, Manjula,Rozzell, J. David,Novick, Scott J.
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p. 10923 - 10929
(2007/10/03)
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- Resolution of non-protein amino acids via the microbial protease-catalyzed enantioselective hydrolysis of their N-unprotected esters
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In the Aspergillus oryzae protease-catalyzed ester hydrolysis, substitution of N-unprotected amino acid esters for the corresponding N-protected amino acid esters resulted in a large enhancement of the hydrolysis rate, while the enantioselectivity was deteriorated strikingly when the substrates employed were the conventional methyl esters. This difficulty was overcome by employing esters bearing a longer alkyl chain such as the isobutyl ester. Utilizing this ester, amino acids carrying an aromatic side chain were resolved with excellent enantioselectivities (E=50 to >200). With amino acids bearing an aliphatic side chain also, good results in terms of the hydrolysis rate and enantioselectivity were obtained by employing such an ester as the isobutyl ester. Moreover, the enantioselectivity proved to be enhanced further by conducting the reaction at low temperature. This procedure was applicable to the case where the enantioselectivity was not high enough even by the use of the isobutyl ester.
- Miyazawa, Toshifumi,Imagawa, Kiwamu,Minowa, Hiroe,Miyamoto, Toyoko,Yamada, Takashi
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p. 10254 - 10261
(2007/10/03)
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- Amine-boranes: Effective reducing agents for the deracemisation of DL-amino acids using L-amino acid oxidase from Proteus myxofaciens
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The deracemisation of DL-α-amino acids using L-amino acid oxidase from Proteus myxofaciens and amine-boranes as chemical reducing agents has been investigated. Amine-boranes were found to be of particular interest in terms of reactivity and chemoselectivity compared to sodium borohydride and cyanoborohydride. Starting from the racemate, a range of D-amino acids were obtained in yields of up to 90% and e.e. >99%.
- Alexandre, Fran?ois-René,Pantaleone, David P.,Taylor, Paul P.,Fotheringham, Ian G.,Ager, David J.,Turner, Nicholas J.
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p. 707 - 710
(2007/10/03)
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- Enantioselective synthesis of α-amino acids and monosubstituted 1,2- diamines by conjugate addition of 4-phenyl-2-oxazolidinone to nitroalkenes
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The addition of the potassium salt of (R)- or (S)-4-phenyl-2- oxazolidinone to monosubstituted nitroalkenes proceeded with very good diastereoselectivity. Several of the addition products were converted into α-amino acids and monosubstituted 1,2-diamines of high enantiomeric purity.
- Lucet, Denis,Sabelle, Stephane,Kostelitz, Olivier,Le Gall, Thierry,Mioskowski, Charles
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p. 2583 - 2591
(2007/10/03)
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- Chemo-enzymatic synthesis of optically active amino acids and peptides
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The industrial alkaline protease, alcalase, is stable and active in a high concentration of organic solvents and useful as a biocatalyst for (i) diastereoselective hydrolysis of peptide esters and preparation of racemization-free peptides; (ii) selective incorporation of esters of D-amino acid into peptides in t-butanol via a selective hydrolysis of esters of D,L-amino acid, followed by using the unhydrolyzed D-esters as a nucleophile in a kinetically controlled peptide bond formation; (iii) resolution of esters of amino acid in 95% t-butanol/5% water, followed by saponification of the unreacted esters to offer both enantiomers with high yield and optical purity; (iv) completely resolve amino-acid esters with high yield and optical purity via in situ racemization of the unreacted antipode catalyzed by pyridoxal 5-phosphate; (v) cryobioorganic synthesis of peptides with increased yields 15%-40% of peptide bond formation by reaction at 5 °C instead of 25-30 °C of a kinetically controlled enzymatic reaction in alcohols.
- Chen, Shui-Tein,Wang, Kung-Tsung
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p. 301 - 311
(2007/10/03)
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- Enantioselective synthesis of α-amino acids from nitroalkenes
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The products of the conjugate addition of (R)-4-phenyl-2-oxazolidinone on monosubstituted nitroalkenes, were converted into D-α-amino acids of high enantiomeric purity.
- Sabelle, Stephane,Lucet, Denis,Le Gall, Thierry,Mioskowski, Charles
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p. 2111 - 2114
(2007/10/03)
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- Schiff bases of amino acid esters as new substrates for the enantioselective enzymatic hydrolysis and accompanied asymmetric transformations in aqueous organic solvents
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The enzyme (lipases and chymotrypsin)-catalyzed hydrolysis of Schiff bases derived from racemic amino acid esters and aromatic aldehydes has been investigated. The reactions were successfully carried out in different aqueous organic solvents at ambient temperature, but the aqueous acetonitrile (5.4% water content by volume) was the solvent of choice. The L-amino acid (ee 98%) precipitated out from the solution as the reaction progressed, and the liberated aldehyde and unhydrolyzed D-ester (ee 40-98%) remained in the solution. The range of substrates included amino acids having different types of side chains. The addition of an organic base (DABCO) into the solution resulted in the racemization of the remaining D-ester and the additional hydrolysis of the substrate, thus leading to the effective asymmetric transformation of the initial ester. Upto 87.5% of the initial racemate was converted into the L-enantiomer.
- Parmar, Virinder S.,Singh, Amarjit,Bisht, Kirpal S.,Kumar, Naresh,Belokon,Kochetkov,Ikonnikov,Orlova,Tararov,Saveleva
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p. 1223 - 1226
(2007/10/03)
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- Chemo-Enzymic Synthesis of Optically Active α,α-Disubstituted α-Amino Acids
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A series of α,α-disubstituted α-amino esters was chemically synthesized and then resolved through enantioselective hydrolysis catalysed by a new enzyme isolated from crude Humicola langinosa lipase.This enzyme only accepts free amino esters as substrates with neither lipase activity toward olive oil nor esterase activity toward o-nitrophenyl butyrate.It is unique in that it successfully catalyses the resolution of amino esters with two large α-alkyl groups including aliphatic, aromatic and cyclic amino esters.Examples of resolutions where the alkyl groups differ in size by as little as a single carbon atom have been demonstrated.For determination of absolute configuration, some of the optically active α,α-disubstituted amino acids were also prepared through Schoellkopf's asymmetric synthesis and the structures were verified by X-ray crystallography.A model depicting the substrate binding site of the enzyme is proposed.
- Liu, Weiguo,Ray, Paul,Benezra, Steven A.
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p. 553 - 560
(2007/10/02)
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- Asymmetric synthesis of α-amino acids by copper-catalyzed conjugate addition of Grignard reagents to optically active carbamatoacrylates
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Optically active ene carbamates were α-lithiated by lithium tetramethylpiperidide in the presence of trialkylstannyl chlorides to produce α-stannylated compounds. These underwent facile palladium-catalyzed couplings with acid chlorides to produce α-keto ene carbamates in good yield. Treatment of the α-stannyl ene carbamates with butyllithium followed by quenching with carbon dioxide and esterification gave optically active carbamatoacrylates. Copper-catalyzed addition of tert-butyl-, 1-naphthyl-, 2-propenyl-, p-methoxyphenyl-, (trimethylsilyl)methyl-, cyclohexyl-, 1-adamantyl-, and isopropyl Grignard reagents followed by quenching at -10 to 25°C and removal of the protecting groups gave the corresponding α-amino acids in 70-90% yield and 73-97% ee. Quenching the reaction at low temperature resulted in little if any asymmetric induction.
- Lander, Peter A.,Hegedus, Louis S.
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p. 8126 - 8132
(2007/10/02)
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- Resolution of amino acids in a mixture of 2-methyl-2-propanol/water (19:1) catalyzed by alcalase via in situ racemization of one antipode mediated by pyridoxal 5-phosphate
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Procedures for the conversion of a racemic amino acid into the L-enantiomer by the alcalase catalyzed resolution of the amino acid ester in 2-methyl-2-propanol/water (19:1) simultaneously with the pyridoxal 5-phosphate-catalyzed racemization of the unhydrolyzed antipode have been developed.
- Chen,Huang,Wang
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p. 7580 - 7581
(2007/10/02)
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- Plasmid-based, D-aminopeptidase-catalysed synthesis of (R)-amino acids
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The gene for D-aminopeptidase from Ochrobactrum anthropi SCRC Cl-38 was cloned in Eschericha coli JM 109.An expression plasmid pCl138DP (4.5 kb) was constructed.The amount of the enzyme in a cell-free extract of E. coli JM109/pCl138DP was elevated up to 288000 units/liter culture, which is about 3600-fold over that of O.anthropi SCRC Cl-38.It was calculated that the enzyme comprised about 30percent of the total extractable cellular protein.The intact cells of the E.coli transformant were used as a catalyst for (R)-stereospecific hydrolysis of several racemic amino amides HCl.Complete hydrolysis of (R)-alanine amide was achieved in a short time (4 1/2 h) from 5.0M racemic alanine amide HCl using cells of the E.coli transformant.The concentration of (R)-alanine reached 220 g/l.The cells or the cell-free extract catalyzed the synthesis of (R)-2-aminobutyric acid, (R)-methionine, (R)-norvaline and (R)-norleucine from their amides in a similar manner.
- Asano, Yasuhisa,Kishino, Katsuhiko,Yamada, Akiko,Hanamoto, Sawako,Kondo, Kiyosi
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p. 206 - 208
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF α-AMINO ACIDS FROM α-HALOGENATED 10-SULFONAMIDO-ISOBORNYL ESTERS.
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Treatment of chiral α-haloesters 2 with NaN3 gave azidoesters 3 wich on successive transesterification and hydrogenolysis furnished α-amino acids 5 and 9 in high e.e.
- Oppolzer, Wolfgang,Pedrosa, Rafael,Moretti, Robert
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p. 831 - 834
(2007/10/02)
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- A General and Practical Synthesis of (R)-Phthalimido Aldehydes and D-α-Amino Acids from D-Mannitol
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A short and practical synthesis of five D-α-amino acids is described from D-mannitol as the chiral educt.The key steps in the sequence are (a) the erythro-selective addition of organometals to (R)-2,3-O-isopropylideneglyceralaldehyde, (b) the Mitsunobu inversion substituting N-phthalimide for hydroxyl, and (c) acetonide hydrolysis and glycol cleavage to give the N -phthaloyl-(R)-α-aminoaldehydes 7.These are oxidized under Jones conditions to give the N-protected amino acids 8.The examples investigated (alanine, aminobutyric acid, norvaline, and allyl- and vinylglycine) demonstrate the general applicability of the method.
- Mulzer, Johann,Angermann, Alfred,Schubert, Boris,Seilz, Carsten
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p. 5294 - 5299
(2007/10/02)
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- Mimics of Transaminase Enzymes
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Pyridoxamine has been attached to the primary side and to the secondary side of β-cyclodextrin; the resulting compounds convert α-keto acids to amino acids with substrate selectivity and some stereoselectivity.Pyridoxamine has also been attached to a synthetic macrocycle; the attached binding group showed substrate selectivity.Chains carrying catalytic basic groups have been attached to pyridoxamine; appropriate systems catalyze the prototropic rearrangement characteristic of transamination.A catalyzed HCl elimination involving chloropyruvic acid was observed.A tetrahydroquinoline system related to pyridoxamine was synthesized to permit the stereochemically defined placement of a basis catalytic group.This converted keto acids to amino acids with good stereoselectivity for the formation of optically active products.
- Breslow, R.,Czarnik, A. W.,Lauer, M.,Leppkes, R.,Winkler, J.,Zimmerman, S.
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p. 1969 - 1979
(2007/10/02)
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- Use of LRH and LRH agonists
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The use of LRH and LRH agonists as contraceptives in the planetal mammal is disclosed.
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- ASYMMETRIC SYNTHESIS AND RETRORACEMISATION OF AMINO ACIDS VIA COPPER(II) COMPLEXES WITH SCHIFF BASES BETWEEN CHIRAL 1-(N,N-DIMETHYLAMINOMETHYL)-2-FORMYLCYMANTRENE AND DIPEPTIDES
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1-(N,N-Dimethylaminomethyl)-2-formylcymantrene (AFCMT) has been resolved into enantiomers through an intermediate formation of diastereomeric complexes with (S)-Ala-(S)-Ala, (S)-Ala-Gly and Gly-(S)-Ala.By the X-ray anomalous dispersion method the absolute configuration of its enantiomers has been determined: (-)436 AFCMT-(S), (+)436 AFCMT-(R).Alkylation of enantiomeric complexes (R) and (S)-AFCMT-(GlyGly) Cu(II) with acetaldehyde gives, respectively, (R)- and (S)-Thr with an asymmetric yield of 92-98percent and (R)- and (S)-allo-Thr with an asymmetric yield of 95-100percent, only the N-terminal glycine being alkylated.The AFCMT enantiomers were also employed for retroracemisation of (R,S)-Ala-(R,S)-Nva; in this case an excess of (S)-Ala and (R)-Nva is obtained for (S)-AFCMT. (R)- and (S)-AFCMT are not liable to racemisation in the course of the threonine synthesis and retroracemisation of dipeptides and can be repeatedly employed for these transformations.
- Belokon', Yu. N.,Zel'tzer, I. E.,Loim, N. M.,Tsiryapkin, V. A.,Aleksandrov, G. G.,et al.
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p. 1089 - 1098
(2007/10/02)
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