P-Hydroxyphenyl acetic acid

However, irradiation of buffered solutions of esters of the p-hydroxy phenacyl at room temperature leads to the rapid release of carboxylate anion with the formation of p-hydroxyphenyl acetic acid ° (1-91) (Scheme 1.42). 

NADH and NADPH, the respective reduced forms of NAD and NADP, are highly fluorescent hence, all NAD" "- and NADP -dependent reactions involved in enzymatic assays can be monitored fluorimetrically with a sensitivity higher than those of absorptiometric techniques by two or three orders of magnitude. Reactants must be used at much lower concentrations, and detection limits of 10 moll or even lower can be achieved. Numerous methods for enzyme determination involve the use of substrates that are transformed into highly fluorescent products. For instance, p-hydroxyphenyl-acetic acid has been used widely as a substrate for the determination of several oxidases such as glucose oxidase and xanthine oxidase. 

Helgeson, E., and Davis, J. M. Simultaneous Determination by GC-MS-SIM of 0-, m-, p-Hydroxyphenyl-acetic Acid, 3,4-Dihydroxyphenyl-acetic Acid and Homovanillic Acid in Biological Samples Using a Common Selected Ion J. Chromatogr. Sci. 16(6) 263-267 (1978) CA 89 175847w... 

Hydroxindole acetic acid-O-sulphate Hydroxylation 3, 6 i -Hydroxymandelic acid 28 p-Hydroxymandelic acid 12 /w-Hydroxyphenyl acetic acid 27 u-Hydroxyphenyl acetic acid 28 p-Hydroxyphenyl acetic acid 26 Hydroxypropylamine 54 5-Hydroxytryptamine see Serotonin... 

C6-C2 Phenylacetic acid p-Hydroxyphenyl-acetic acid COOH... 

Fig. 2 The effect of three phenolic acids on the Chi content of 2-week-old rice seedling. A. o-Hydroxyphenyl acetic acid B. ferulic acid and C. p-Coumaric acid. Kimura s culture solution contains 0, 25, 50, or 100 ppm of either o-hydroxyphenyl acetic, ferulic or p-coumaric acids. Extraction was done on liquid-nitrogen frozen leaves with 80% acetone. The data is mean of three determinations and the bars indicate the standard deviation (Yang et al. 2002, 2004).

Bunton and Hellyer studied the oxidation of p-hydroxyphenyl acetate and benzoate, 2,5-di-ierl.-butyl-p-quinol, and 3-ferf.-butyl-4-hydroxyphenyl acetate in aqueous solutions in the range pH 0.5-3.0 at 25 °C. The oxidations are second-order (first with respect to each reactant) and in the case of the esters the products are the p-quinone, iodate, and acetic or benzoic acids. The rates of oxidation of p-hydroxyphenyl acetate and benzoate are very similar. The steric effect of the rcrl.-butyl group, substituted into p-quinol and p-hydroxyphenyl acetate, is to reduce the rate by almost the same factor in both cases. Bunton and Hellyer concluded that the mechanisms of oxidation of quinol and its esters by periodate are the same, and that the rate-determining step is the electrophilic attack of either... 

A significant increase in the measured COj concentration was observed after the addition of 10 mmol/1 of a-keto-isovaleric acid (148% increase from baseline), a-keto-isocaproic acid (120%), phenylacetic acid (100%), DL-a-keto-P-methyl-A-valeric acid (100%), homogentisinic acid (50%), P-phenylpyruvic acid (45%), hydroxyphenyl acetic acid (32%), propionic acid (25%), ace-toacetic acid (25%), hydroxyphenyl pyruvate acid (23%), and 20 mmol/1 of hydroxyphenyl lactid acid (65%) or salicylic acid (76%). A significant decrease was observed after the addition of 20 mmol/1 of ascorbic acid (33%), DL- -hydroxybutyric acid (25%) or imidazole lactic acid (25%). No effect after the addition of 10 mmol/1 of imidazole-4-acetic acid, methylmalonic acid, 5-hy-droxyindole acetic acid or 20 mmol/1 arginosuccinic acid, Z.-(+)-hydroxybu-tyric acid (E525). 

D-(— )-a-amino-a-(4-hydroxyphenyl)acetamido]-3-methyl-3-cephem-4-carbojQ lic acid (6i ,7i )-7-[(fi)-2-amino-2-(p-hydroxyphenyl) acet imido]-8-oxo-3-propenyl-5-thia-l-azabicyclo[4.2.0]oct-2-ene-2-carbo3Qrlic acid... 

Ethylenediiminobis[(2-hydroxyphenyl)acetic acid] (EHPG) (Other values on Vol.l, p.96)... 

To a solution of 7 (d-p-hydroxyphenyl-0i-carboxyacetamido-7(l-methoxy-3-(1-methyl-tetrazol-5-vl)thiomethyl-1-oxadethia-3-cephem4-carboxylic acid (359 mg) in methanol (7 ml) is added a solution of sodium 2-ethylhexanoate in methanol (2 mols/liter 1.73 ml) at room temperature. After stirring for 10 minutes, the reaction mixture is diluted with ethyl acetate, stirred for 5 minutes, and filtered to collect separated solid, which is washed with ethyl acetate, and dried to give disodium salt of 7 (a-p-hydroxyphenyl-a-carboxyacetamido)-7Q -methoxy-3-(1-methyl-tetrazol-5-vl)thiomethyl-1-oxadethia-3-cephem4-carboxylic acid (342 mg). Yield 885%. Colorless powder. MP decomposition from 170°C. 

After 6 hours the calculated amount of hydrogen has been taken up. The residue obtained after filtering and evaporating is taken up in benzene and extracted twice with diluted sodium carbonate solution. The alkali extract is then made acid to Congo red with 6N hydrochloric acid and the precipitate is taken up in ethyl acetate. The solution obtained is washed twice with salt solution, dried with sodium sulfate and evaporated. The residue is recrystallized from ether/petroleum ether. 1-(p-hydroxyphenyl)-2-phenyl-4-n-butyl-3,5-dioxo-pyrazolidine melts at 124° to 125°C. 

The p-benzoxy-a-bromopropiophenone and l-phenyl-3-amino-butane were heating for an hour on the water bath in the absence of solvents. A solid crystalline cake was obtained. After being extracted with boiling acetic acid, the hydrobromide of l-(p-hydroxyphenyl)-2-(p-phenylbutylamino)propanone-l was obtained. 

Treatment of some a-ethynyl acetates with a mixture of nitrosyl fluoride and nitrosonium tetrafluoroborate affords bis[(acetoxyalkyl)carbonyl]furoxans the presence of the a-acetoxy group appears to be essential (81JOC312). Monosubstituted furoxans have been obtained by nitrosation of unsaturated hydrocarbons thus the reaction of nitrous acid with p -hydroxycin-namic acid affords 3-(p-hydroxyphenyl)furoxan, its structure being confirmed by X-ray crystallography (80LA1557). 

A neutral solution of 28 grams of 8-amino-5-acetamido-4-hydroxyphenyl-arsinic acid (p. 309) in dilute aqueous sodium hydroxide is diluted to ISO c.c. and rapidly added to an aqueous suspension of cyanogen bromide (freshly prepared from 18 grams of bromine) and the whole well stirred. After standing for about an hour the product is acidified with acetic acid, the brown precipitate treated in alkaline solution with charcoal, and reprecipitated. "White, prismatic needles result (20 grams yield), readily soluble in alkalis and dilute mineral acids. 

Fierz-David and Ziegler (301) first applied this method to azo compounds. Ethyl acetoacetate and various aromatic amines (aniline, o- and p-toluidines, m-xylidine, o-anisidine, and chloroanilines) were convereted to acetoacetanilides and then coupled with diazotized sulfanilic acid. The azo dyes (38) were reduced with stannous chloride in hydrochloric acid to the corresponding aminoaceto-acetanilides (39), which in alkali formed the dihydropyrazines (40). Catalytic reduction of o-hydroxyphenylglyoxal phenylhydrazone in acetic acid over palladium has been shown also to give 2,5-bis(o-hydroxyphenyl)pyrazine (302). Reduction of chemical means has been shown to give... 

Diastereoselective [2+2] photocycloaddition of a polymer-supported cyclic chiral enone with ethylene has been reported (Scheme 12.33) [43]. The auxiliary was derived from (-)-8-(p-methoxyphenyl) menthol (87). Protection of the secondary alcohol and demethylation were carried out to give (-)-8-(p-hydroxyphenyl)menthyl acetate (88). An alkyl linker was introduced and finally loaded to poly (ethylene glycol) grafted Wang resin. Deprotection of the alcohol functionality was followed by esterification with cyclohexen-3-one-l-carboxylic acid to provide the chiral enone 89. The photochemical reaction with ethylene was performed by irradiating with light (k > 280 nm). Trifluoroacetic acid (TFA) or aqueous hydrolysis with... 

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