Phenylalanine 4 -nitro

A phenomenon related to the chain-effect has been observed [76] when polymeric catalysts containing basic units in the chain are employed to initiate the polymerization of DL-j3-phenylalanine-, 4-nitro-DL- 3-phenylalanine- and 2,4-dinitro-DL-j3-phenylalemine-NCAs. The enhance-... 

Analytical applications of pyrazolones have been reviewed by Busev et al. (65RCR237). Organic bases are easily characterized by formation of highly crystalline salts with picrolonic acid (l-(4-nitrophenyl-3-methyl-4-nitro-5-hydroxypyrazole). The last-named compound is used as a reagent for alkaloids, tryptophan, phenylalanine and for the detection and estimation of calcium (B-76MI40404). 

Diethyl-p-nitrobenzyl-phthalimidomalonate (70 g) and sodium carbonate (70 g) in water (700 ml) were refluxed overnight with mechanical stirring (to avoid bumping). The clear brown solution was acidified with hydrochloric acid and refluxing and stirring were continued for a further 40 minutes. The mixture was cooled and the colorless precipitate (31 g) collected. A second crop (18.5 g) was obtained on evaporation of the mother liquors. Crystallization from aqueous ethanol gave the compound N-carboxybenzoyl-p-nitro-DL-phenylalanine as small needles, MP 198° to 200°C. 

The N-carboxybenzoyl compound (2.7 g) was refluxed for 30 minutes with acetic anhydride (10 ml), the mixture taken to dryness (vacuum) and the residue heated with water. The cooled gummy product became granular on rubbing and crystallized from methyl ethyl ketone-petrol or aqueous ethanol in almost colorless needles, MP 184° to 186°C, of p-nitro-N-phthaloyl-D L-phenylalanine. 

A solution of p-nitro-N-phthaloyl-DL-phenylalanine (1.0 g) in methanol (25 ml) and a solution of cinchonidine (0.865 g) in methanol (30 ml) were mixed. Crystallization soon set in. The mixture was left overnight, and the colorless needles (0,97 g), MP 209° to 210°C, collected. After two recrystallizations from methanol the cinchonidine salt of the D-acid had MP 211°C,... 

MP 191° to 192,5°C, Two recrystallizations from aqueous ethanol gave the cinchonidine salt of the L-acid, MP 192,5° to 194°C. To the salt (2.9 g) in warm ethanol (50 ml) was added water (50 ml) and a slight excess (ca 10 ml) of N aqueous sodium hydroxide. The mixture was diluted with water, cooled, filtered from the precipitated base and the filtrate acidified with hydrochloric acid. Refluxing with 2 N ethanolic hydrogen chloride yielded p-nitro-N-phthaloyl-L-phenylalanine ethyl ester, according to U.S. Patent 3,032,585. 

C,H, N204 949-99-5) see Melphalan Zolmitriptan 4-nitro-L-phenylalanine ethyl ester monohydrochloride (C, H 5C1N204 58816-66-3) see Melphalan... 

The substrate used was the synthetic peptide N-Succinyl-Alanine-Alanine-Proline-Phenylalanine p-Nitroanilide which upon hydrolysis liberates 4-Nitro-aniline which is conveniently measured at 410 nm. 

The chiral purity of amino acids at large enantiomeric excess can be determined automatically by derivatization with 4-fluoro-7-nitro-2,l,3-benzoxadiazole (127b) followed by CE with cyclodextrin chiral selectors and detection of the LIF excitation at 488 nm. Lod 140 ppm of L-phenylalanine in D-phenylalanine324. 

Peroxynitrite (ONOO ) is a cytoxic species that is considered to form nitric oxide (NO) and superoxide (Oj ) in biological systems (Beckman et al. 1990). The toxicity of this compound is attributed to its ability to oxidize, nitrate, and hydroxylate biomolecules. Tyrosine is nitrated to form 3-nitrotyrosine (Ramazanian et al. 1996). Phenylalanine is hydroxylated to yield o-, m-, and p-tyrosines. Cysteine is oxidized to give cystine (Radi et al. 1991a). Glutathione is converted to S-nitro- or S-nitroso derivatives (Balazy et al. 1998). Catecholamines are oxidatively polymerized to melanin (Daveu et al. 1997). Lipids are also oxidized (Radi 1991b) and DNA can be scissored by peroxynitrite (Szabo and Ohshima 1997). 

Zolmitriptan (2, BW-311C90) was discovered by Wellcome in the United Kingdom and then transferred to AstraZeneca upon the acquisition of Wellcome by Glaxo (now GlaxoSmithKline). The synthesis began with 4-nitro-L-phenylalanine (29), which was converted to the methyl ester and then reduced with NaBHj to give the amino alcohol (Scheme 8). ° Oxazolidinone 30 was formed by treating the amino alcohol... 

Chromophoric leaving group.2-4 The original work on p-nitrophenyl acetate has been extended by synthesizing p-nitrophenyl esters of specific acyl groups, such as acetyl-L-phenylalanine, -tyrosine, and -tryptophan. The rate of acylation of the enzyme is determined from the rate of appearance of the nitro-phenol or nitrophenolate ion, which absorbs at a different wavelength from the parent ester. 

Figure 27.18 Common configuration for postcolumn reactors with electrochemical analysis. (A) LC-chemical reaction-EC. Postcolumn addition of a chemical reagent (for example, Cu2+ or an enzyme). (B) LC-enzyme-LC. Electrochemical detection following postcolumn reaction with an immobilized enzyme or other catalyst (for example, dehydrogenase or choline esterase). (C) LC-EC-EC. Electrochemical generation of a derivatizing reagent. The response at the second electrode is proportional to analyte concentration (for example, production of Br2 for detection of thioethers). (D) LC-EC-EC. Electrochemical derivatization of an analyte. In this case a compound of a more favorable redox potential is produced and detected at the second electrode (for example, detection of reduced disulfides by the catalytic oxidation of Hg). (E) LC-hv-EC. Photochemical reaction of an analyte to produce a species that is electrochemically active (for example, detection of nitro compounds and phenylalanine). Various combinations of these five arrangements have also been used. [Reprinted with permission from Bioanalytical Systems, Inc.]...

A method utilizing the Dess-Martin periodinane[12 for the conversion of a peptide a-hy-droxy ester into the corresponding a-oxo ester was reported by Burkhart et al.[8l The final product, peptide a-oxo ester, obtained in this process contains a mixture of enantiomers at C2 in PI of the peptide. The optical impurity arises not from the oxidation reaction but the synthesis of one of the intermediates, 2-hydroxy-3-nitro-4-phenylbutanoic acid, which generates four diastereomers at two adjacent chiral carbons. This procedure is limited to the synthesis of peptide a-oxo esters with the phenylalanine residue at the PI position. A more diversified approach is achieved by using a-hydroxy- 3-amino acids 14 as the key intermediate that permits selective introduction of an amino acid residue at PI of the peptide it can also be coupled to N-protected amino acids or N-protected peptides and further transformations give a-oxo esters 19, a-oxo acids 20, and a-oxoamides 22 (Scheme 4)J3 61... 

The asymmetric synthesis of the C(2) diastereomer of amprenavir was also accomplished, similarly starting from N-tert-butoxycarbonyl-(S)-phenylalaninal (19), where the requisite chiral ammonium fluoride 4e was generated in situ from the corresponding bromide 3e in the initial nitro aldol process (Scheme 9.8) [18]. 

Chiral iminopyridines catalyse nitro aldol reactions with good ees in the pres- ence of copper(II) acetate, without the need for exclusion of air or moisture.143 A (g) phenylalanine-derived Schiff base - also complexed to copper(II) - is also effective, with the advantage that product configuration is easily reversed (by using the enantiomeric phenylalanine).144... 

Melphalan and the racemic analog have been prepared by two general routes (Scheme I). In Approach (A) the amino acid function is protected, and the nitrogen mustard moiety is prepared by conventional methods from aromatic nitro-derivatives. Thus, the ethyl ester of N-phthaloyl-phenylalanine was nitrated and reduced catalytically to amine I. Compound I was reacted with ethylene oxide to form the corresponding bis(2-hydroxyethyl)amino derivative II, which was then treated with phosphorus oxychloride or thionyl chloride. The blocking groups were removed by acidic hydrolysis. Melphalan was precipitated by addition of sodium acetate and was recrystallized from methanol. No racemization was detected [10,28—30]. The hydrochloride was obtained in pure form from the final hydrolysis mixture by partial neutralization to pH 0.5 [31]. Variants of this approach, used for the preparation of the racemic compound, followed the same route via the a-acylamino-a-p-aminobenzyl malonic ester III [10,28—30,32,33] or the hydantoin IV [12]. 

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