P-Bromophenylacetic acid

The carboxylic acid formed by free-radical chlorination of p-bromotoluene, followed by nitrile synthesis and hydrolysis is p-bromophenylacetic acid. 

Mauthner, J. prakt, Chem., 1917, 95, 62. Berger, J. prakt, Chem., 1932,133, 345. p>Bromophenylacetic Acid (p-Bromo a-ioluic (tcid). 

Alkylation of the dianion of 3-bromophenylacetic acid (10) with p-chlorobenzyl chloride was accomplished using IiHMDS in THF to afford the substituted acid 11. The only significant impurity was the bis-alkylated product, which could be minimized by control of the reaction temperature to below -20 °C to give an 88%... 

As deduced from the DNA sequence of the gene, AMDase contains four cysteine residues. Since a-halocarboxylic acids are generally active alkylating agents there is a possibility that a-bromophenylacetic acid reacts with several cysteine residues of the enzyme. Therefore, we tried to clarify how many cysteine residues react with this inhibitor. It is well established that when p-chloromercuri-benzoate (PCMB) binds to a cysteine residue, the absorbance at 255 nm increases due to the formation of an aryl-Hg-S bond. Thus it is possible to estimate the number of free S-H residues of the enzyme by titration with PCMB solution (Fig. 6). When the native enzyme had reacted with PCMB, the absorbance at 255 nm increased by 0.025. On the other hand, when PCMB solution was added to the enzyme solution after the enzyme was incubated with a-bromophenyl-... 

Method C2 (typical catalytic procedure).A 5% solution of NaBH4 in 5% aqueous NaOH is added dropwise under N2 to a solution of a-bromophenylacetic acid (1.50 g, 7.0 mmol) and bis(2-thienyl) ditelluride (0.30 g, 0.71 mmol) in EtOH (40 mL) until the red colour of the ditelluride just disappears. At this point air is infioduced in the system to oxidize the catalyst back to the ditelluride. The mixture is then partitioned in ether/5% aqueous NaOH. The aqueous phase is separated, acidified with 2 M HCl and extracted with ether. The extract is dried (CaCl2) and evaporated to give phenylacetic acid (0.93 g (98%) m.p. 77°C). 

Carboxylic acids, acyl chlorides, and sulfonyl chlorides used for deri-vatization of 4-aminophenylalanine and >-4-am i n op h e ny I a I a n i n e are as follows 5-hydantoinacetic acid, / ran, v - 4 - co t i n i n ec a r b o xy I i c acid, isonicotinic acid, 3-pyridinepropionic acid, 4-hydroxyphenylacetic acid, 2-butynoic acid, 2-pyrazinecarboxylic acid, cyclopropanecarboxylic acid, 3-hydroxy-2-qui-noxaline carboxylic acid, 5-bromovaleric acid, propargyl chloroformate, 3,4-dimethoxybenzoyl chloride, 2-thiophenesulfonyl chloride, 3-thiophene-carboxylic acid, 2-thiophenecarboxylic acid, 2-methylbutyric acid, 2-thio-pheneacetyl chloride, benzoic acid, furylacrylic acid, 4-nitrophenyl acetic acid, 2,5-dimethoxyphenylacetic acid, p-toluenesulfonyl chloride, 4-(di-methylamino)phenylacetic acid, 3-indolepropionic acid, phenoxyacetic acid, 3-(dimethylamino)benzoic acid, cyclohexanecarboxylic acid, naphtha-lenesulfonyl chloride, 4-bromophenylacetic acid, 4-bromobenzoic acid, 2-phenoxybutyric acid, 3,4-dichlorophenylacetic acid, (l-naphthoxy)acetic acid. 

Therefore the contribution of substrate binding to the reaction rate is partially due to a change in the molecularity of the reaction. The intermolecular reaction of the two substrates is replaced by an intramolecular reaction of an enzyme-substrate complex. The consequences can be clarified by using model compounds which have all the reactive groups within their molecules and, thus, are subjected to an intramolecular reaction. Their reactivity can then be compared with that of the corresponding bimolecular system and the results expressed as a ratio of the reaction rates of the intramolecular (ki) to the intermolecular (k2) reactions. Based on their dimensions, they are denoted as effective molarity . As an example, let us consider the cleavage of p-bromophenylacetate in the presence of acetate ions, yielding acetic acid anhydride ... 

To a stirred mixture of phenylboronic acid (260, 0.30 g, 2.5 mmol, 1.1 eq.), methyl 4-bromophenylacetate (264, 0.52 g, 2.25 mmol), and powdered cesium fluoride (0.76 g, 5.0 mmol, 2 eq.) in DME (8 ml) was added Pd(PPh3)4 (87 mg, 3 mol%). The reaction mixture was flushed with argon and maintained refluxed under argon for 24 h. The mixture was then cooled and diluted with ethyl acetate (20 ml) and water (20 ml), and the ethyl acetate layer was dried (Na2S04), and concentrated. From the crude product, 0.50 g (98%) of pure methyl biphenyl-4-acetate (265), m.p. 19-21 C, was isolated by preparative chromatography on silica gel using n-hexane / ethyl acetate (5 1) as an eluent. 

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