0.0-Dimethyl phosphate

In the body, metrifonate converts to the active metaboUte dichlorvos, (2,2-dichlorovinyl dimethyl phosphate), which is responsible for the inhibition of the enzyme acetylcholinesterase in the susceptible worm. This effect alone is unlikely to explain the antischistosomal properties of metrifonate (19). Clinically, metrifonate is effective only against infection caused by S. haematobium. Metrifonate is administered in three doses at 2-wk intervals (17). The dmg is well tolerated. Side effects such as mild vertigo, nausea, and cramps are dose-related. This product is not available in the United States. The only manufacturer of metrifonate is Bayer A.G. of Leverkusen, Germany. 

The use of TMSOTf and thioanisole results in rapid (t./, = 7 min) cleavage of one methyl in a dimethyl phosphate, whereas the second methyl is cleaved only slowly (t./ =12 h). The method has been further refined for peptide synthesis. " ... 

Exposure Levels in Humans. Methyl parathion has been detected in serum and tissue shortly after acute exposure (EPA 1978e Ware et al. 1975). It is rapidly metabolized and does not persist in serum and tissues for long (Braeckman et al. 1983). Two metabolites of methyl parathion, 4-nitrophenol and dimethyl phosphate, can be detected in urine and tissues for up to 2 days following exposure (Morgan et al. 1977). These compounds are specific for methyl parathion when there is a history of exposure. 

In the reaction of the very reactive phosphoric triimidazolide (for preparation see Section 2.2), which is also called phosphoryltriimidazole in analogy to the carbonyldii-midazole CDI, with an excess of methanol, as products trimethyiphosphate, dimethyl-phosphate, and O-methylphosphoric imidazolide were detected after one hour, and after two days the imidazolium salt of dimethylphos-phate was obtained in high yield [13]... 

The reaction of 151 with methanol to give dimethyl phosphate (154) or with N-methylaniline to form the phosphoramidate 155 and (presumably) the pyrophosphate 156 complies with expectations. The formation of dimethyl phosphate does not constitute, however, reliable evidence for the formation of intermediate 151 since methanol can also react with polymeric metaphosphates to give dimethyl phosphate. On the other hand, reaction of polyphosphates with N-methylaniline to give 156 can be ruled out (control experiments). The formation of 156 might encourage speculations whether the reaction with N,N-diethylaniline might involve initial preferential reaction of monomeric methyl metaphosphate via interaction with the nitrogen lone pair to form a phosphoric ester amide which is cleaved to phosphates or pyrophosphates on subsequent work-up (water, methanol). Such a reaction route would at least explain the low extent of electrophilic aromatic substitution by methyl metaphosphate. 

Berthod, H., and A. Pullman. 1975. The Molecular Electrostatic Potential of the Dimethyl Phosphate Anion An Ab Initio Study. Chem. Phys. Lett. 32, 233. 

Takayama and coworkers (60) introduced the h.p.l.c. separation technique for such amphiphilic molecules as lipid A, and in earlier experiments they applied paired-ion reverse-phase h.p.l.c. for the preparation of homogeneous fractions deriving from 4,-monophosphated lipid A of S. typhimur-ium. The purified preparations obtained were suitable for f.a.b. - m.s. analysis. However, monophosphated lipid A isolated in this way expressed a considerable heterogeneity with respect to the number and location of 0-acyl residues (60). In order to further improve the purification procedure, as well as to obtain lipid A derivatives suitable for n.m.r. spectroscopy, Qureshi et al. (174) prepared the dimethyl phosphate derivative of S. minnesota (R595) lipid A, which, after purification by reverse-phase h.p.l.c. (C18), could be analyzed by1 H-n.m.r. The n.m.r. spectrum of, for example, the heptaacyl lipid A dimethyl monophosphate fraction, unequivocally revealed 0-acyl substitution [14 0(3-OH)J at position 3 and a free hydroxyl group at position 4 of GlcN(I). 

Exposure Levels in Humans. No data on disulfoton levels in various human tissues and body fluids of a control population, populations near hazardous waste sites, or occupationally exposed groups in the United States are available. The levels of disulfoton metabolites (DEP [0.05 ppm], DETP [0.04 ppm], DEPTh [0.008 ppm], dimethyl phosphate [0.04 ppm], dimethyl thiophosphate [0.180 ppm], and dimethyl phosphorothiolate [0.004 ppm]) in the urine of disulfoton formulators have been measured (Brokopp et al. 1981). Data on the levels of disulfoton and its metabolites in body tissues and fluids are needed to estimate the extent of exposure to disulfoton. 

Figure 3.13. Titration of the fluorescence of anthrylpolyamine 6 by various added anions, o, phosphate ion , sulfate ion O, acetate ion Q, dimethyl phosphate ion , citrate ion +, TBAC1 ion.

Dichlorvos (9.50) is an insecticide of reportedly wide use, the metabolites of which in humans include dichloroethanol and dimethyl phosphate. Like paraoxon, dichlorvos is hydrolyzed by human serum. However, the enzyme activities hydrolyzing the two substrates were shown to differ by a number of criteria [114], Clearly large gaps remain in our understanding of the human metabolism of organophosphorus insecticides and other toxins. A bacterial phosphodiesterase appears as a promising tool to understand the catalytic mechanisms of organophosphoric acid triester detoxification [115-117],... 

Plant. Metabolites identified in cotton leaves include dimethyl phosphate, phosphoric acid, methyl phosphate, and CTdimethyl dichlorvos (Bull and Ridgway, 1969). The estimated half-life of dichlorvos applied to selected ornamental flower crops is 4.8 h (Brouwer et al, 1997). 

Photolytlc. Malathion absorbs UV light at wavelengths more than 290 nm indicating direct photolysis should occur (Gore et al, 1971). When malathion was exposed to UV light, malathion monoacid, malathion diacid, 0,0-diethyl phosphorothioic acid, dimethyl phosphate, and phosphoric acid were formed (Mosher and Kadoum, 1972). 

Dichloroethenyl dimethyl phosphate, see Dichlorvos l,l -(Dichloroethenylidene)bis(4-chlorobenzene), seep,p ... 

Dimethyl phosphate of methyl-3-hydroxy-ds-crotonate, see Mevinphos... 

Methoxyaniline, see o-Anisidine p-Methoxyaniline, see p-Anisidine 2-Methoxybenzenamine, see o-Anisidine 4-Methoxybenzenamine, see p-Anisidine p-Methoxybenzenamine, see p-Anisidine Methoxycarbonylethene, see Methyl acrylate Methoxycarbonylethylene, see Methyl acrylate 2-Methoxycarbonyl-l-methylvinyl dimethyl phosphate, see... 

Plant. In cotton leaves, the metabolites identified included dichlorvos, phosphoric acid, 0-demethyl dichlorvos, 0-demethyl trichlorfon, methyl phosphate, and dimethyl phosphate (Bull and Ridgway, 1969). Chloral hydrate and trichloroethanol were reported as possible breakdown products of trichlorfon in plants (Anderson et al, 1966). 

Lieberman, M.T. and Alexander, M. Microbial and nonenzymatic steps in the decomposition of dichlorvos (2,2-dichlor-ovinyl 0,0-dimethyl phosphate), / Agric. Food Chem., 31(2) 265-267, 1983. 

Phosphate-derived a-oxycarbanions can rearrange into a-hydroxy phosphonates. This class of rearrangement is known to proceed with retention of configuration at the carban-ion terminus. The enantioselective version of this rearrangement has been developed using a chiral lithium amide as a base (equation 115) . The reaction of benzyl dimethyl phosphate 182 with amide R,R)-63 in THF gave the hydroxy phosphonate (5 )-183 in 30% in enantioenriched form (52% ee). 

In two cases of moderate intoxication from mevinphos, urinary excretion of dimethylphos-phate (a metabolite of mevinphos) was almost complete 50 hours after exposure/ Although a number of other organophosphorus pesticides also yield dimethyl phosphate, the presence of significant amounts of this metabolite in the urine may be useful in estimating the absorption of mevinphos. 

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