A synergistic effect on the DHPA-induced growth inhibition of S. cerevisiae was observed when tyrosine was added to the medium. Superior conversions were obtained with benzaldehydes bearing electron withdrawing groups, such as nitro (1 b), cyano (1 c), or acetyl (1 i), because of the increased electrophilic reactivity. Although some wild‐type threonine aldolases have the unique property to accept few d‐amino acids as donor, further sequence search or enzyme engineering based on directed evolution or rational design may lead to the development of catalysts with broader donor specificity, as recently shown for other aldolases. Additionally, methods to remove the β‐hydroxyl group in serine derivatives were investigated. A single (R)‐syn‐diastereomer was isolated from the reaction with 3‐fluoro‐benzaldehyde ((m)‐1 f) and dl‐alanine catalyzed by d‐TA (Table 3, Entry 8). CHD- lies 186 kJ mol-1 lower in energy than HCPD- (4-31G//STO-3G). In recent years, threonine aldolase enzymes able to accept alanine as a donor were found via screening and database mining15 or created via engineering of an alanine racemase17 or l‐serine hydroxymethyltransferase,18 and thus make these enzymes ideal catalysts for the direct synthesis of α‐quaternary α‐amino acids starting from aldehydes and amino acids. You need to know what count and milligram your Sudafed or whatever you choose to cook with is. To investigate the possible role of serine as a precursor of dehydroalanine at the active site of phenylalanine ammonia lyase, two serines, conserved in all known PAL and histidase sequences, were changed to alanine by site-directed mutagenesis. Synthetic Opportunities of Ion-Radical Organic Chemistry. Enantioselective synthesis of precursors for cis-hydrindanes. article provided that the correct acknowledgement is given with the reproduced material. The diastereomers can be typically separated by flash‐chromatography on reversed‐phase silica gel. l-2,5-Dihydrophenylalanine has been isolated from cultures of two strains of Streptomyces. ... 1,4-Dihydro--phenylalanine—Its Synthesis and Behavior in the Phenylalanine Ammonia–Lyase Reaction. about the reduction of phenylalanine to amphetamine. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Authors contributing to RSC publications (journal articles, books or book chapters) (0.61g, 94%) as a white crystalline solid. thank the Land of Baden-Württemberg for a scholarship for graduate students. . Your Mendeley pairing has expired. Ugi-Reaktion führt zu N-Trifluoracetyl-2,5-cyclohexadien-1-alanin-methylamid (2). For reproduction of material from all other RSC journals and books: For reproduction of material from all other RSC journals. Matthias Boll, Georg Fuchs, Johann Heider. Anaerobic oxidation of aromatic compounds and hydrocarbons. Thus, (S)‐α‐methylphenylalanine, a valuable non‐natural amino acid, which is used in peptidomimetics and as sweetener, was produced using a simple two‐step chemo‐enzymatic synthesis starting from inexpensive benzaldehyde and alanine in an overall yield of 10 % and an e.e. Influence of alkyl substituents on the π* negative ion states of benzene and its derivatives. The mixture was recooled to 0°C and D-phenylalanine The Birch reduction of 2-acyl or 2-acyl-5-alkylthiophenes and subsequent alkylation by alkyl halides gave 2-acyl-2-alkyl or 2-acyl-2,5-dialkyl-2,5-dihydrothiophenes in good yields. D.R. To a stirred, chilled (0°C) solution of D-phenylalaninol (5 g, 33.1 mmol) in 85 ml of chloroform was added solid di-tert-butyl dicarbonate (7.22g, To this was added 6 ml of a 1.0 M HCl solution At increasing aldehyde concentration, some inactivation of the enzymes was observed, and thus continuous feeding of the acceptor substrate turned out to be advantageous. The authors would like to acknowledge the financial support from the Austrian Science Fund FWF: Hertha‐Firnberg project T735‐B21. Guanidine hydrochloride also brings about the Type I to Type II conversion.The enzyme functions catalytically by converting the NH3+ of l-phenylalanine into a better leaving group. The codon of Ser-202 was changed to those of alanine and threonine by site-directed mutagenesis. The aromatic ring in L-phenylalanine was transformed into isoxazolyl, N-phenylpyrazolyl, and the bicyclic pyrazolo[1,5-a]pyrimidinyl groups, by a combination of Birch reduction and ozonolysis, followed by condensation with the relevant binucleophiles. Analogously, the (R)‐isomer can be obtained from (2R)‐2‐amino‐3‐hydroxy‐2‐methyl‐3‐phenylpropanoic acid 3 a, synthesized by d‐TA. On comparing the above substrate analogue with L-phenylalanine, the Km was lowered only slightly but kcat was reduced 14--40-fold depending on the source of the enzyme. A Birch‐type reduction enabled the reductive removal of the β‐hydroxy group from (2S)‐2‐amino‐3‐hydroxy‐2‐methyl‐3‐phenylpropanoic acid to generate enantiopure l‐α‐methyl‐phenylalanine via a two‐step chemo‐enzymatic transformation. Synthetic procedures have been developed to provide 2,3-disubstituted-3,4-dihydro-1(2H)-isoquinolinones 6, 10, and 15 from (1R,2S)-ephedrine, (1R,2R)-pseudoephedrine, and l-phenylalanine. The structure assigned to the product is confirmed by its 1H nuclear magnetic resonance spectrum and by the chemical synthesis to be described in a subsequent paper. The structure of the unsubstituted cyclohexadienyl radical has been fully optimized and substituents (CH3, CN, COOH, NO2, COO-, F, OCH3, OH, and NH2) have been sited in the 1, 2, 3, or 6 positions. Among those, aldolases proved to be efficient biocatalysts for the stereoselective carbon‐carbon bond formation,13 however, they are known for their strict specificity towards nucleophiles which limits the accessible product range.
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