Methyl 4-nitrophenyl phosphate

Potentiometry was used to investigate the speciation of La(ni) in methanolic methox-ide solutions, with and without diphenyl phosphate or methyl 4-nitrophenyl phosphate (98), substrates which are very efficiently methanolysed by such solutions.2 La(III)-catalysed methanolysis is thus regarded as a good model for the metal-containing RNAses and DNases which cleave phosphate diester linkages. In the high [La(III)] domain, the data fitted, as one possibility among several, a spontaneous decomposition... 

Brown and Neverov ° provided clear evidence for complex formation of anionic phosphate diesters to one as weU as two lanthanide metal ions (La ). The La -catalyzed methanolysis of anionic methyl 4-nitrophenyl phosphate revealed the rate acceleration of 3.3 x 10 -fold with one La and 1.7 x 10 -fold with two La at pH 8.5. Large rate acceleration due to lanthanide catalysis has been explained in terms of plausible transition states TS and TSy, which show the occurrence of bifunctional catalysis (Lewis acid and nucleophilic). 

As is apparent from Fig. 1, the dianions of monoalkyl phosphates normally resist hydrolysis. However, for leaving groups whose conjugate acids exhibit a pKa < 5 in water, hydrolysis of the dianion becomes faster than that of the monoanion. Fig. 2 shows a pH profile characteristic of this situation. Whereas the hydrolysis rate of 2,4,6-trichlorophenyl phosphate (pKa of the phenol 6.1) still shows the typical monoanion preference as seen for methyl phosphates (Fig. 1), the dianion of 2,4-dinitrophenyl phosphate (pKa of the phenol 4.09) is hydrolyzed far faster than the monoanion 2-chloro-4-nitrophenyl phosphate represents an intermediate case (pKa of the phenol 5.45)6S). 

Also, Chin s dihydroxy-bridged dicobalt(III) complex 10 provides one of the largest rate enhancements ever observed for phosphodiester hydrolysis [36]. Reaction with the activated phosphodiester methyl(p-nitrophenyl)phosphate (MNPP) yields 11. A crystal structure is available for the analogous dimethylphosphate complex in which the Co ions are 2.9 A apart. At pH 7 and 45 °C 11 releases p-nitrophenolate with k = 0.1 s 1 which corresponds to a nearly 10I2-fold rate enhancement over spontaneous hydrolysis of the substrate. The product of the reaction is a methylphosphate-bridged complex. Based on the pH rate profile and on... 

Loran and Williams, 1977. The reference intermolecular reaction is the attack of pyridine on methyl o-nitrophenyl phosphate (Kirby and Younas, 1970). Corrections for the conversion to a diaryl ester and a p-nitrophenyl leaving group are assumed to cancel out. Temperature correction uses E, = 14.8 kcal mol-1, as measured for the reference reaction 4 Lazarus et al., 1980... 

Many organic chemicals are analyzed by RPC. These include various arylhydroxylamines as the N-hydroxyurea derivative with methyl isocyanate (614) alkyl- and alkoxy-disubstituted azoxybenzenes (6t5), n-alkyl-4-nitrophenylcarbonate esters ranging in length from methyl to octyl (616), 4-nitrophenol in the presence of 4-nitrophenyl phosphate (617), ben-zilic acid, and benactyzine-HCI using ion-pair chromatography (618), as well as aniline and its various metabolites (619), stereoisomers of 4,4 -dihydroxyhydrobenzoin (620), and aldehydes and ketones as the 2,4-dinitrophenylhydrazones (621). The technique has also been used to analyze propellants and hydrazine and 1,1-dimethylhydrazine were quantitita-vely determined (622, 623). 

Comparison of Second-Order Rate Constants (M 1sec 1) in Hydrolysis (or Acetyl and Phosphoryl Transfer) of 4-Nitrophenyl Acetate, Methyl Acetate and Bis(4-nitrophenyl) Phosphate... 

Nitrophenyl acetate0 ) Methyl acetate6 (MA) Bis(4-nitrophenyl) phosphate A(BNP-)... 

In practice it is often more convenient to measure the release of a phenol from an aryl phosphomonoester. Standard serum phosphatase methods employ phenyl phosphate (188), p-nitrophenyl phosphate (189), phenolphthalein monophosphate (140), or thymolphthalein monophosphate (141) where the phenol released can be determined spectrophoto-metrically [only the Bodansky method (13) uses a Pi determination]. A number of fluorogenic substrates have been used for phosphatase studies, e.g., jS-naphthyl phosphate (30, 148), 4-methylumbelliferyl phosphate (143), and 3-O-methylfluorescein phosphate (144) The main advantage here is the much greater sensitivity of fluorescence as compared with spectrophotometric assays as little as 1 pmole of 4-methyl-umbelliferone can be detected in continuous assay. 

Methyl-p-nitrophenyl phosphate coordinated to the two metal centers in 37 undergoes hydrolysis by a two-step addition-elimination mechanism [73]. The free phosphate hydrolyzes by a concerted mechanism. In both phosphate monoester and diester hydrolysis, the two Co(m) centers in 32 and 37 stabilize the five-coordinate phosphate species (transition state or intermediate) by bringing the phosphate and nucleophile together. This stabilization leads to a change in mechanism from dissociative to concerted for a phosphate monoester hydrolysis [96] and from concerted to stepwise for phosphate diester hydrolysis [73]. 

Inhibition of lipases, both by the substrate or the product, has been observed. In alcoholysis of methyl propanoate with n-propanol catalyzed by Candida antarctica lipase B (CALB), the alcohol was found to inhibit the enzyme resulting in a deadend complex [21]. Phosphate- and phosphonate-conlaining inhibitors are known to inhibit proteases. Studies of the inhibition of CALB have shown inhibition by diethyl p-nitrophenyl phosphate. The inactivation of the enzyme was caused by covalent binding of diethyl p-nitrophenyl phosphate in the active site [22]. 

HIAA. A ready-to-use competitive EIA kit has been developed for measuring chemically derivatized 5-HIAA. In this procedure, dichloromethane is used to convert 5-HIAA to its methyl ester during sample preparation. This methylated derivative competes with biotin-labeled 5-HIAA for a limited number of binding sites of an antibody immobilized on microtiter plates. After incubation, the wells are washed to remove unbound biotin-labeled HIAA and then incubated with antibiotin alkaline phosphatase before a p-nitrophenyl phosphate substrate is added. The amount of biotinylated HIAA bound to the antibody is inversely proportional to the 5-HIAA concentration. This EIA method shows excellent correlation with HPLC, and interassay reproducibility coefficient of variation (CV) is about 7% at a 5-HIAA level of 7.5mg/L. 

Mono- and binuclear Zn(II) nitrate complexes of the bis(l-methylimidazol-2-yl-methyl)ethylamine and N,N,N, N -tetrakis( 1 -methylimidazol-2-ylmethyl)pentane- 1,5-diamine ligands (Fig. 51) catalyze the hydrolysis of tris-4-nitrophenyl phosphate... 

A binuclear zinc complex of the 2,6-bis [(2-pyridylmethyl)(2-hydroxyethyl) amino]methyl -4-methylphenol ligand (L33, Fig. 63) catalyzes the hydrolysis of bis(4-nitrophenyl) phosphate in aqueous buffer solution to yield 4-nitrophenol and 4-nitrophenyl phosphate.246 Analysis of the pH-rate profile revealed a sigmoidalshaped curve with a pKa = 7.13. This value is similar to a deprotonation event characterized by potentiometric titration and has been assigned to deprotonation of... 

Nedoma et al. (2003) compared values of cell-specific activity (surface phosphomonoesterase activity per cell) obtained in their own study of two waterbodies in the Czech Republic (10-2260 fmol/cell/h, methylumbelliferyl phosphate) with those in the literature. These include (expressed as fmol/cell/h) Phaeocystis, 2.5 (methyl fluorescin phosphate van Boekel and Veld-huis, 1990) Nannochloris, 0.5-5.5 [para-nitrophenyl phosphate Lubifin et al.,... 

Staurastrum chaetoceras, 10 para-nitrophenyl phosphate Spijkerman and Coesel, 1998) Chlamydomonas reinhardtii, 3000-22,000 (methyl fluorescin phosphate Joseph et al., 1994). 

Organophosphorus reagents that inhibit hydrolases (serine hydrolases) diethyl p-nitrophenyl phosphate (paraoxon) diisopropyl phosphofluoridate (DFP) dimethyl(dichlorovinyl) phosphate (dichlovos) O -methylphosphoramidothioate 3-hydroxy-N-methyl-cis-crotonamide dimethylphosphate tetraethyl pyrophosphate (TEPP)... 

Diethyl pyrocarbonate has been used to convert uridine 2 - or 3 -phosphate into the 2, 3 -cyclic phosphate in high yield, and an adamantyl 2, 3 -cyclic phosphonate (421) was obtained when uridine reacted with I-adamantylphos-phonyl chloride. Phosphorylation of ribonucleosides with pyrophosphoryl chloride followed by hydrolysis in neutral solution afforded a simple synthesis of ribonucleoside 2, 3 -cyclic phosphate 5 -phosphates. Two phosphorylating agents mentioned earlier in this section can also yield 3, 5 -cyclic phosphates either by treatment of nucleoside 5 -(2-iV7V-dimethylamino-4-nitrophenyl phosphates) with acetic acid in pyridine (Scheme I4i) i, 83 qj. treatment of nucleoside 5 -(5 -methyl phosphorothioates) with iodine in pyridine. Another route to 3, 5 -cyclic phosphates involved cyclization of the nucleoside 5 -trichIoro-methylphosphonates (422) (obtained by the action of trichloromethylphosphonyl... 

The earliest reported demonstration of enzymatic activity in a supercritical fluid was for the reaction of disodium p-nitrophenyl phosphate to p-nitro-phenol, catalysed by alkaline phosphatase. Randolph et aL [26] detected the product in yields of up to 71% in carbon dioxide at 35°C and 100 atm, in the presence of 0.1% v/v water. Hammond et al. [33] found tyrosinase, a polyphenol oxidase, to be catalytically active for the oxidation of 4-methyl phenol in both supercritical carbon dioxide at (36 2)°C and supercritical trifluoro-methane at (34 2)°C, with oxygen, at a total pressure of 345 bar. Use of a flow reactor permitted isolation of greater quantities of the catecholic product (1,2-dihydroxy, 4-methylbenzene). Oxidative activity for 4-chlorophenol substrate was appreciably lower. 

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