Phosphorous acid diesters esters

HO A phosphoric acid monoester HO A phosphoric acid diester 0 1 R" A phosphoric acid triester A carboxylic acid ester... 

This property of organophosphate esters may be of environmental importance since phosphoric acid diesters are much more soluble and very little is known concerning the environmental toxicity of these compounds. The available data do not provide sufficient descriptions of the experimental methods to determine if the rates are reliable (Barnard et al. 1961 Ciba-Geigy 1984e, 1986 Howard and Deo 1979 Mayer et al. 1981 Wolfe 1980). The majority of reports provide only a minimum of information and exclude important facts such as the duration of the experiments and the concentration of buffers. Despite the lack of experimental detail, published rate constants for base-catalyzed hydrolysis appear to be reasonably consistent and suggest that the hydrolytic half-life of triphenyl phosphate will vary from... 

Homer-Wadsworth-Emmons reactions are C=C-forming condensation reactions between the Li, Na, or K salt of a /1-koto- or an a-(alkoxycarbonyl )phosphomc acid dialkyl ester and a carbonyl compound (see Figure 4.46). These reactions furnish a,/3-unsaturated ketones or 0 ,/3-unsaturated esters, respectively, as the desired products and a phosphoric acid diester anion as a water-soluble by-product. In general, starting from aldehydes, the desired compounds are produced /ra/ov-selectively or, in the case of alkenes with trisubstituted C=C double bonds, -selectively. 

DCC is also used in nucleotide chemistry to esterify a sugar hydroxyl group with a phosphate group in another nucleotide or oligonucleotide unit. Also p-styrene based polymers with a pyridyl-2-ethanol end group are reacted in pyridine with 3 -0-acetyl-desoxythimidine-5 -phosphate in the presence of DCC." The reaction of mono esters of phosphoric acid with alcohols or phenols, in the presence of DCC, affords phosphoric acid diesters in high yield." This reaction is widely used in nucleic acid chemistry. 

This reaction is very exothermic and rapid removal of the hydrogen chloride formed must be provided for, to prevent dealkylation of the ester formed. The phosphorous acid diesters can be purified by distillation. 

One important phospholipid is phosphatidylcholine, also called lecithin. Phosphatidylcholine is a mixture of diesters of phosphoric acid. One ester function is derived... 

Phosphonic acid esters from phosphorous acid diesters (RO)2P(0)H - (R0)2P(0)R from Na-salt cf. 4, 604 electrochemical method s. V.A. Petrosyan, M.E. Niyazym-betov, Izv. Akad. Nauk SSSR Ser. Khim. 1988, 1945. 

Phosphoric acid A phosphoric acid monoester A phosphoric acid diester A phosphoric acid tri ester... 

Phosphoric acid diesters from phosphorodichloridates—Simultaneous removal of protective groups s. 13, 284 Pyrophosphoric acid esters... 

Phosphoric acid diesters s. 17, 171 also unsym. pyrophosphoric acid esters s. Soc. 196A, 326... 

We have synthesized a TADDOL-based phosphoric acid diester (47), which catalyzed the Mannich-type reaction of ketene silyl acetal with aldimines to give p-amino esters with high enantioselectivity. (Scheme 2.104) [180]. 

Just as waxes, fats, and oils are esters of carboxylic acids, phospholipids are diesters of phosphoric acid, H3PO4. 

When a mixture of phosphoric acid and phosphoric acid esters is titrated with a sodium hydroxide solution two potential jumps can be observed. The first jump results from the acid group of the diester, the first neutralization step of the monoester, and the first neutralization step of free phosphoric acid. The second potential jump is caused by the second neutralization steps of the monoester and of the free phosphoric acid. The third step of neutralization of the free phosphoric acid cannot be covered by this method. Titration of acid esters can only be used for the determination of mono- and diesters of phosphoric acid when the amount of free phosphoric acid is separately ascertained. 

Phosphotriesterase from P. diminuta (PTE) was found to exhibit high hydrolytic activity towards various types of tetracoordinated phosphorus acid esters. Apart from the phosphonothionate 92, phosphoric acid triesters 94 (Equation 45), °" benzenephosphonic acid diester 95 (Equation 46) ° and methyl-phenylphosphinic acid ester 96 (Equation 47) were also stereoselectively hydrolysed under kinetic resolution conditions. Of course, in the case of the latter three kinds of substrates, half of the reacting ester was irreversibly lost due to the formation of achiral phosphorus acids. 

Hydrolysis appears to be the most important abiotic degradative mechanism for organophosphate esters under basic pH conditions. Under neutral and acidic conditions, the reaction slows considerably and could become an insignificant removal mechanism. The hydrolysis proceeds by a stepwise mechanism in which one alcohol group is removed at a time. The first step is cleavage of a P-OR bond (where "R" is an aryl or alkyl group) to produce a diester of phosphoric acid, which, under basic conditions, becomes an anion. 

Tetrazolides of phosphorous acid esters or amides have been developed for the phos-phitilation of nucleosides. For instance, the tetrazolide of the diester of phosphorous acid (Af-tetrazolyldiethoxyphosphine) can be prepared either from diethylchlorophosphite and sodium tetrazolide (Method A) or from diethoxydiisopropylaminophosphine and two equivalents of tetrazole. The latter reaction (Method B) was undertaken to verify formation of a tetrazolide in the activation of phosphoramidites by tetrazole.[27]... 

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