- Reactivity of α-Amino Acids in the Reaction with Esters in Aqueous–1,4-Dioxane Media
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The kinetics of the reaction of a series of α-amino acids with 4-nitrophenyl acetate, 4-nitrophenyl benzoate, and 2,4,6-trinitrophenyl benzoate in aqueous 1,4-dioxane medium has been studied. Kinetics of the reactions involving 4-nitrophenyl acetate and 2,4,6-trinitrophenyl benzoate has complied with the Br?nsted dependence and revealed linear correlation between rate constant logarithm and the energy difference of the frontier orbitals of α-amino acids anions.
- Kochetova,Kustova,Kuritsyn
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- Formation and hydrolysis of amide bonds by lipase A from Candida antarctica; Exceptional features
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Various commercial lyophilized and immobilized preparations of lipase A from Candida antarctica (CAL-A) were studied for their ability to catalyze the hydrolysis of amide bonds in N-acylated α-amino acids, 3-butanamidobutanoic acid (β-amino acid) and its ethyl ester. The activity toward amide bonds is highly untypical of lipases, despite the close mechanistic analogy to amidases which normally catalyze the corresponding reactions. Most CAL-A preparations cleaved amide bonds of various substrates with high enantioselectivity, although high variations in substrate selectivity and catalytic rates were detected. The possible role of contaminant protein species on the hydrolytic activity toward these bonds was studied by fractionation and analysis of the commercial lyophilized preparation of CAL-A (Cat#ICR-112, Codexis). In addition to minor impurities, two equally abundant proteins were detected, migrating on SDS-PAGE a few kDa apart around the calculated size of CAL-A. Based on peptide fragment analysis and sequence comparison both bands shared substantial sequence coverage with CAL-A. However, peptides at the C-terminal end constituting a motile domain described as an active-site flap were not identified in the smaller fragment. Separated gel filtration fractions of the two forms of CAL-A both catalyzed the amide bond hydrolysis of ethyl 3-butanamidobutanoate as well as the N-acylation of methyl pipecolinate. Hydrolytic activity towards N-acetylmethionine was, however, solely confined to the fractions containing the truncated form of CAL-A. These fractions were also found to contain a trace enzyme impurity identified in sequence analysis as a serine carboxypeptidase. The possible role of catalytic impurities versus the function of CAL-A in amide bond hydrolysis is further discussed in the paper. The Royal Society of Chemistry 2010.
- Liljeblad, Arto,Kallio, Pauli,Vainio, Marita,Niemi, Jarmo,Kanerva, Liisa T.
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scheme or table
p. 886 - 895
(2010/06/20)
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- Microwave-assisted synthesis of amide under solvent-free conditions
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An efficient and environmentally friendly synthetic method for the synthesis of primary amides under microwave irradiation was described, in which the primary amine was directly reacted with acid without any catalytic agents. The reaction took place in 8-12-min, which was much shorter than the traditional synthetic methods, with almost quantitative yields. The influential factor of the reaction was discussed. The tautomerization between the carboxylic acid group and the H atom in α-carbon of L-amino acid was observed, presumably a dehydrated intermediate forming from this tautomerized isomer. Copyright Taylor & Francis Group, LLC.
- Wang, Xiao-Jian,Yang, Qian,Liu, Fei,You, Qi-Dong
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p. 1028 - 1035
(2008/09/18)
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- Amidoearbonylation of aldehydes utilizing cobalt oxide-supported gold nanoparticles as a heterogeneous catalyst
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Cobalt oxide-supported gold-nanoparticles-catalyzed transformation of aldehydes and their equivalents to N-acyl-α-arnino acids was achieved. The desired products were obtained in moderate to excellent yields under milder reaction conditions than previous reports employing octacarbonyldicobalt as a catalyst. Copyright
- Hamasaki, Akiyuki,Liu, Xiaohao,Tokunaga, Makoto
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supporting information; experimental part
p. 1292 - 1293
(2009/12/03)
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- Novel phosphine ligands
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The invention is concerned with new phosphine ligands of the formula I wherein R1 and R2 are independently of each other alkyl, aryl, cycloalkyl or heteroaryl, said alkyl, aryl, cycloalkyl or heteroaryl may be substituted by alkyl, alkoxy, halogen, hydroxy, amino, mono- or dialkylamino, aryl, —SO2—R7, —SO3?, —CO—NR8R8′, carboxy, alkoxycarbonyl, trialkylsilyl, diarylalkylsilyl, dialkylarylsilyl or triarylsilyl; R3 is alkyl, cycloalkyl, aryl or heteroaryl; R4′ and R4 signify independently of each other hydrogen, alkyl or optionally substituted aryl; or R4′ and R4 together with the C-atom they are attached to form a 3-8-membered carbocyclic ring; dotted line is absent or is present and forms a double bond; R5 and R6 are independently of each other hydrogen, alkyl or aryl; or linked together to form a 3-8-membered carbocyclic ring or an aromatic ring; R7 is alkyl, aryl or NR8R8′; and R8 and R8′ are independently of each other hydrogen, alkyl or aryl; metal complexes with such ligands as well as the use of such metal complexes as catalysts in asymmetric reactions.
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Page/Page column 24-25
(2010/11/27)
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- METHOD OF AMIDOCARBONYLATION REACTION
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A novel method of an amidocarbonylation reaction among an aldehyde compound, an amide compound, and carbon monoxide, which comprises using a palladium-supporting crosslinked-polymer composition containing palladium clusters having a major-axis length of 20 nm or shorter to conduct the amidocarbonylation reaction. Thus, an N-acyl-±-amino acid can be more efficiently and selectively synthesized in a clean reaction system. Also provided is a catalyst for use in the method.
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Page/Page column 11
(2008/06/13)
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- Palladium-catalyzed amidocarbonylation improved by recyclable ionic liquids
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Two types of ionic liquids (halide anion ionic liquids and Brensted acidic ionic liquids) were first applied to improve the palladium-catalyzed amidocarbonylation. Both the palladium catalyst and the ionic liquids could be recycled at least five times without significant loss in catalytic activity. Georg Thieme Verlag Stuttgart.
- Zhu, Bingchun,Jiang, Xuanzhen
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p. 2795 - 2798
(2008/02/11)
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- A study of amidocarbonylation reactions catalyzed by Pd/HZSM-5
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A HZSM-5-supported palladium catalyst, which was prepared by the conventional impregnation method, was utilized in amidocarbonylation reactions. Several important parameters were optimized to give moderate to excellent yields. The catalyst recycling of Pd/HZSM-5, for the first time, was achieved for at least four run times without depreciation of catalytic activity. The studies of TEM images revealed that agglomeration of the palladium species of Pd/ HZSM-5 catalyst was avoided after reaction, which was quite different from the case of Pd/C catalyst.
- Ke, Wu Yang,Xuan, Zhen Jiang
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p. 806 - 809
(2007/10/03)
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- Efficient synthesis of N-acyl-α-amino acids via polymer incarcerated palladium-catalyzed amidocarbonylation
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A novel polymer incarcerated Pd catalyst (PI Pd 7c) was synthesized from amide-containing polymer 6b, and this catalyst was shown to be effective in amidocarbonylation, which is a versatile one-pot method for the preparation of N-acyl-α-amino acids. The reactions proceeded smoothly with a wide variety of substrates, and no leaching of the Pd metal to the reaction mixture was detected.
- Akiyama, Ryo,Sagae, Takahiro,Sugiura, Masaharu,Kobayashi, Shu
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p. 3806 - 3809
(2007/10/03)
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- Platinum-catalyzed amidocarbonylation
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The first example of platinum-catalyzed amidocarbonylation of aldehydes with amides and carbon monoxide is described. In contrast to precedent palladium catalysis, a remarkable ligand acceleration by phosphines was observed. Furthermore, an optically active N-acetyl amino acid was partially epimerized under the platinum-catalyzed conditions, while faster racemization was observed under the palladium catalysis.
- Sagae, Takahiro,Sugiura, Masaharu,Hagio, Hiroyuki,Kobayashi, Shu
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p. 160 - 161
(2007/10/03)
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- Heat-stable D-aminoacylase
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The present invention provides a novel D-aminoacylase, as well as method for producing a D-amino acid using the same. In order to achieve the above objective, the present inventors have succeeded in purifying heat-stable D-aminoacylase from microorganisms belonging to the genus Streptomyces by combining various purification methods. Furthermore, the present inventors found that the purified heat-stable D-aminoacylase is useful in industrial production of D-amino acids. By utilizing the heat-stable D-aminoacylase, it is possible to readily and efficiently produce the corresponding D-amino acids from N-acetyl-DL-amino acids (for example, N-acetyl-DL-methionine, N-acetyl-DL-valine, N-acetyl-DL-tryptophan, N-acetyl-DL-phenylalanine, N-acetyl-DL-alanine, N-acetyl-DL-leucine, and so on).
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- Enantioselective hydrolytic reactions of rice bran lipase (RBL): A first report
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Enantioselectivity has been observed in the hydrolysis of racemic N-acetyl amino acid esters with rice bran lipase (RBL). The enzyme shows selectivity towards the (S)-enantiomer. Products with high enantiomeric excess (e.e. >99%) are obtained depending upon the hydrophobicity of the amino acid as well as that of the leaving group.
- Fadnavis,Jadhav, Vasudev
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p. 2361 - 2366
(2007/10/03)
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- A novel tea-bag methodology for enzymatic resolutions of α-amino acid derivatives in reverse micellar media
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A novel tea bag methodology for resolution of methyl esters of N-acetyl- α-amino acids in reverse micellar medium of bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) in isooctane-chloroform using immobilized enzymes or microbial cells is presented. The methodology effectively solves the problems of substrate solubility, product separation and surfactant recycling and provides products in high yields (80 to 90%) and excellent optical purities (% ee 97 to >99%).
- Bhalerao,Rao,Fadnavis
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p. 2109 - 2118
(2007/10/02)
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- Kinetic Resolution of Unnatural and Rarely Occuring Amino Acids: Enantioselective Hydrolysis of N-Acyl Amino Acids Catalyzed by Acylase I
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Acylase I (aminoacylase; N-acylamino-acid amidohydrolase, EC 3.5.1.14, from porcine kidney and the fungus Aspergillus) is broadly applicable enzymatic catalyst for the kinetic resolution of unnatural and rarely occuring α-amino acids.Its enantioselectivity for the hydrolysis of N-acyl L-α-amino acids is nearly absolute, yet it accepts substrates having a wide range of structure and functionality.This paper reports the initial rates of enzyme-catalyzed hydrolysis of over 50 N-acyl amino acids and analogues, the stabilities of the enzymes in aqueous and aqueous/organic solutions, and the effects of different acyl groups and metal ions on the rates of enzymatic hydrolysis.Eleven α-amino and α-methyl α-amino acids were resolved on a 2-29-g scale.Crude L- and D-amino acid products had generally >90percent ee.The utility of resolved amino acids as chiral synthons was illustrated by the preparation of (R)- and (S)-1-butene oxide and the diastereoselective (cis:trans, 7-8:1) iodolactonization of three 2-amino-4-alkenoic acid derivatives.
- Chenault, H. Keith,Dahmer, Juergen,Whitesides, George M.
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p. 6354 - 6364
(2007/10/02)
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- Efficient Asymmetric Hydrogenations of (Z)-2-Acetamidoacrylic Acid Derivatives with the Cationic Rhodium Complex of (2S,4S)-MOD-BPPM
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The preparation of (2S,4S)-MOD-BPPM ((2S,4S)-N-(t-butoxycarbonyl)-4-phosphino>-2-phosphino>methyl>pyrrolidine) and its application to highly effective asymmetric hydrogenations of (Z)-2-acetamidoacrylic acid derivatives are described.
- Takahashi, Hisashi,Achiwa, Kazuo
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p. 305 - 308
(2007/10/02)
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- A general and accurate nmr determination of the enantiomeric purity of α-aminoacids and α-aminoacid derivatives
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Derivatization of α-aminoacids, α-aminoesters and α-aminolactones as N-acetyl derivatives allow the accurate NMR determination of the enantiomeric purity. In these conditions the major coordination site with a chiral shift reagent will correspond to the NMR observation site. Experimental factors leading to the highest ΔΔδ values are ascertained. No straightforward correlation with absolute configurations can be established.
- Calmes, Monique,Daunis, Jacques,Jacquier, Robert,Verducci, Jean
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p. 2285 - 2292
(2007/10/02)
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- NEW SYNTHETIC ROUTE TO N-ACYL-α-AMINO ACIDS VIA AMIDOCARBONYLATION BY MEANS OF HOMOGENEOUS BINARY CATALYST SYSTEMS
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New catalytic processes which lead to the formation of N-acyl-α-amino acids promoted by homogeneous binary systems are described: (a) the isomerization-amidocarbonylation of allylic alcohols catalyzed by transition metal binary systems, e.g., Co-Rh, Co-Pd, Co-Fe, giving various aliphatic N-acyl-α-amino acids; (b) the isomerization-amidocarbonylation of oxiranes catalyzed by cobalt-Lewis acid systems giving N-acyl-α-amino acids; The process is extremely effective for the synthesis of N-acetylphenylalanine from styrene oxide and (c) the hydroformylation-amidocarbonylation of trifluoropropene catalyzed by cobalt-rhodium binary system giving N-acetyltrifluorovaline in excellent regioselectivity and yield.Possible mechanisms for these new processes are discussed.
- Hirai, Kenji,Fujita, Makoto,Fuchikami, Takamasa
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p. 203 - 214
(2007/10/02)
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- DIRECT CONVERSION OF ALLYLIC ALCOHOLS INTO N-ACYL-α-AMINO ACIDS BY CATALYTIC AMIDOCARBONYLATION BY MEANS OF HOMOGENEOUS BINARY SYSTEMS
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N-Acyl-α-amino acids are synthesized by the amidocarbonylation of allylic alcohols catalyzed by homogeneous binary systems which consist of cobalt carbonyl and rhodium (or iron or palladium) complexes.
- Hirai, Kenji,Takahashi, Yoshitaka,Ojima, Iwao
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p. 2491 - 2494
(2007/10/02)
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