35068-04-3Relevant articles and documents
Oxidative damage of aromatic dipeptides by the environmental oxidants NO2 and O3
Gamon,White,Wille
, p. 8280 - 8287 (2015/01/08)
Irreversible oxidative damage at both aromatic side chains and dipeptide linkage occurs in the aromatic N- and C-protected dipeptides 7-11 upon exposure to the environmental pollutants NO2 and O3. The reaction proceeds through initial oxidation of the aromatic ring by in situ generated NO3, or by NO2, respectively, which leads to formation of nitroaromatic products. The indole ring in Phe-Trp undergoes oxidative cyclization to a pyrroloindoline. An important reaction pathway for dipeptides with less oxidisable aromatic side chains proceeds through fragmentation of the peptide bond with concomitant acyl migration. This process is likely initiated by an ionic reaction of the amide nitrogen with the NO2 dimer, N2O4. This journal is
Differentiation of natural and synthetic phenylalanine and tyrosine through natural abundance 2H nuclear magnetic resonance
Brenna, Elisabetta,Fronza, Giovanni,Fuganti, Claudio,Pinciroli, Matteo
, p. 4866 - 4872 (2007/10/03)
The natural abundance deuterium NMR characterization of samples of the amino acids tyrosine (1) and phenylalanine (2), examined as the acetylated methyl esters 4 and 6, has been performed with the aim to identify by these means the contribution in animals of the hydroxylation of the diet L-phenylalanine (2) to the formation of L-tyrosine (1), a feature previously revealed on the same samples through the determination of the phenolic δ18O values. The study, which includes also the NMR examination of benzoic acid (5) from 2 and of tyrosol (7) from 1, substantially fails in providing the required information because the mode of deuterium labeling of tyrosine samples of different origins is quite similar but indicates a dramatic difference in the deuterium labeling pattern of the two amino acids 1 and 2. The most relevant variation is with regard to the deuterium enrichments at the CH2 and CH positions, which are inverted in the two amino acids of natural derivation. Moreover, whereas the diastereotopic benzylic hydrogen atoms of L-tyrosine (1) appear to be equally deuterium enriched, in L-phenylalanine (2) the (D/H)3R > (D/H)3S. Similarly, benzoic acid (5) shows separate signals for the aromatic deuterium nuclei, which are quite indicative of the natural or synthetic derivation. The mode of deuterium labeling of the side chain of 1 and 2 is tentatively correlated to the different origins of the two amino acids, natural from animal sources for L-tyrosine and biotechnological probably from genetically modified microorganisms for L-phenylalanine.
Modified BINAPO ligands for Rh-catalysed enantioselective hydrogenation of acetamidoacrylic acids and esters
Guo, Rongwei,Au-Yeung, Terry T.-L.,Wu, Jing,Choi, Michael C. K.,Chan, Albert S. C.
, p. 2519 - 2522 (2007/10/03)
(S)- and (R)-2,2′-Bis[bis(3,5-dimethylphenyl)phosphinoyl]-5,5′,6, 6′,7,7′,8,8′-octahydro-1,1′-binaphthyl (Xyl-H8-BINAPO) were synthesised by reacting chlorobis(3,5-dimethylphenyl)phosphine with (S)- and (R)-2,2′-dihydroxyl-5,5′,6,6′,7,7′,8,8′-
