- Mechanism of the Hydrolysis of (Z)-4-Benzylidene-2-methyloxazolin-5-one or (Z)-4-Benzylidene-2-phenyloxazolin-5-one Derivatives
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The methyl (1a) and the phenyl (2) derivatives of (Z)-4-benzylideneoxazolin-5-one were hydrolyzed at comparable rates under alkaline conditions.In contrast, the acidic hydrolysis of 2 was at least 10E5 times slower than that of 1a.The Hammett ρ value obtained from the acidic hydrolysis of the phenyl substituted derivatives of 1a was 0.20 +/- 0.09 while that from the corresponding basic hydrolysis was 1.50 +/- 0.11.Methanolysis of 1a under basic conditions produced the methyl ester of (Z)-α-(acetylamino)cinnamic acid, and that under acidic conditions led to products consistent with the attack of methanol at the imine carbon.These results indicate that the alkaline hydrolysis of the oxazolin-5-one derivatives occurs through nucleophilic attack at the carbonyl carbon of the substrate and the acidic hydrolysis through that at the imine carbon.
- Suh, Junghun,Lee, Eun,Myoung, Young Chan,Kim, Minwoo,Kim, Soodan
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- Preparation method of alpha-ketoleucine calcium dihydrate or alpha-ketophenylalanine calcium monohydrate
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The invention discloses a preparation method of alpha-ketoleucine calcium dihydrate or alpha-ketophenylalanine calcium monohydrate. In an existing method, the quality of a final product is low, and the content of related substances is high. The method comprises the steps that isobutylidene hydantoin or benzal hydantoin is taken as a raw material and generates a pipeline continuous flow ring-opening reaction with an alcohol-water solution of alkali, and then corresponding alpha-ketoacid salt is obtained, wherein the pipeline continuous flow ring-opening reaction is a continuous ring-opening reaction conducted in a pipeline reactor; the obtained alpha-ketoacid salt is firstly extracted with a hydrocarbon solvent or a halohydrocarbon solvent or a ketone solvent or an ether solvent for impurity removal and then acidized to obtain a corresponding crude alpha-ketonic acid product, the crude alpha-ketonic acid product is extracted with the hydrocarbon solvent or the halohydrocarbon solvent or the ketone solvent or the ether solvent for impurity removal, and then a fine alpha-ketonic acid product is obtained; the obtained alpha-ketonic acid is prepared into calcium salt, crystallization is conducted, and the alpha-ketoacid calcium hydrate is obtained. Accordingly, the high-quality and high-purity alpha-ketoleucine calcium dihydrate and alpha-ketophenylalanine calcium monohydrate are obtained.
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Paragraph 0065; 0066; 0067; 0075; 0076
(2017/06/02)
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- Synthesis of isotopically labelled L-phenylalanine and L-tyrosine
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A synthetic route to stable-isotope-substituted L-phenylalanine is presented, which allows the introduction of 13C, 15N, and deuterium labels at any position or combination of positions. For labelling of the aromatic ring, a synthetic route to ethyl benzoate (or benzonitrile) has been developed, based on the electrocyclic ring-closure of a 1,6-disubstituted hexatriene system, with in situ aromatization by elimination of one (amino) substituent. Several important (highly isotopically enriched) synthons have been prepared, namely benzonitrile, benzaldehyde, ethyl benzoate, and ethyl diphenyloxyacetate. Labelled L-phenylalanines have been synthesized from both aromatic precursors by initial conversion into sodium phenylpyruvate and subsequent transformation of this intermediate into the L-α-amino acid by an enzymatic reductive amination reaction. In this manner, highly enriched phenylalanines are obtained on the 10-gram scale and with high enantiomeric purities (≥ 99% ee). The method has been validated by the synthesis of [1'13C]-L-Phe and [2-D]-L-Phe. In addition, two methods are described for the introduction of isotopes into L-tyrosine starting from the isotopically enriched precursors benzonitrile and ethyl benzoate.
- Raap, Jan,Nieuwenhuis, Saskia,Creemers, Alain,Hexspoor, Sander,Kragl, Udo,Lugtenburg, Johan
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p. 2609 - 2621
(2007/10/03)
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- Functinalised Bilayer Vesicle as a Catalyst for Transamination: Artificial Transaminase
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The non-enzymatic transamination reaction of α-amino acids with α-keto acids was investigated in aqueous media at 30 deg C.The functionalised single-walled co-vesicle composed of a synthetic peptide lipid, N,N-dihexadecyl-Nα--L-histidinamide bromide, and a hydrophobic pyridoxal derivative, 1-(NN-dihexadecylcarbamoylmethyl)-2-methyl-3-hydroxy-4-formyl-5-hydroxymethylpyridinium chloride, effectively catalysed amino-group transfer from L-phenylalanine to pyruvic acid in the presence of copper(II) ions, showing turnover behaviour. the catalytic activity of the vesiculer system was much higher than those of 1,2-dimethyl-3-hydroxy-4-formyl-5-hydroxymethyl-pyridinium chloride and pyridoxal examined in aqueous media containing copper(II ions.The rate-determining step involved in the catalytic cycle performed with the vesicular catalyst is primarily assigned to the product-releasing process, the hydrolysis of the copper(II) chelate of the aldimine Schiff's base to afford alanine.
- Murakami, Yukito,Kikuchi, Jun-ichi,Akiyoshi, Kazunari,Imori, Toru
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p. 1919 - 1924
(2007/10/02)
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- Dioxolanones as Synthetic Intermediates. Part 1. Synthesis of α-Keto Acids, α-Keto Aldehydes, and α-Ketols
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2,2-Pentamethylene-1,3-dioxolan-4-one (10) has been elaborated to provide 5'-ylidene derivatives using a Wittig approach.This apparently novel class of compounds is subject to nucleophilic attack at the 4-position because of strain inherent in the 5-membered ring.Thus alkaline hydrolysis leads to the formation of α-keto acids; hydride reduction of dioxolanones incorporating conjugated aryl substituents using di-isobutylaluminium hydride leads to α-keto-aldehydes; the reaction of dioxolanone (15) with methylmagnesium iodide gave the α-ketol (40).
- Ramage, Robert,Griffiths, Gareth J.,Shutt, Fiona E.,Sweeney, John N. A.
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p. 1531 - 1537
(2007/10/02)
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