Benzyl phosphate esters

In the preparation of surfactants by the reaction of alcohols with P4Ol0 with subsequent neutralization of the partial phosphate esters with a base, the quality of the surfactants is improved by using RNEt3OH (R = Et or benzyl) in alcoholic solution as the base, by using C6 10 alcohol mixtures of hydroxyethylated C7 9 alcohols or equimolar mixtures of C6 I0 alcohols with polyethylene glycol (mol wt 200-1500) and by using a reaction temperature of 55-60°C [8]. 

SCHEME 10.2 Common pathways of QM formation in biological systems, (a) Stepwise two-electron oxidation by cytochrome P450 or a peroxidase, (b) Enzymatic oxidation of a catechol followed by spontaneous isomerization of the resulting n-quinone. (c) Enzymatic hydrolysis of a phosphate ester followed by base-catalyzed elimination of a leaving group from the benzylic position. 

Scheme 3) [30]. The pY + 3 diversity alcohols (Ri)-OI I (Fig. 15) were attached to the template through a Mitsunobu coupling to provide ether derivatives of 16. Palladium-mediated Alloc deprotection followed by amide formation using the phosphate-ester-containing diversity acids (R2)-C02H provided the fully coupled resin-bound products of 17. Cleavage from the resin with 95% TFA/H20, which also afforded benzyl phosphate deprotection, followed by reversed-phase (RP) semipreparative... 

The deprotection procedure is based on transesterification of benzyl phosphate into the corresponding silyl ester followed by hydrolysis or alcoholysis. 

Schistosoma japonicum. The carbobenzoxy (CBz) protected template 160 was initially converted to the a, p-dehydrolactone 161 via the phosphate ester, before undergoing cycloaddition to ylide 162, generated in situ by acidic treatment of A(-benzyl-A(-(methoxymethyl)trimethylsilyl amine. The resultant cycloadduct (163) was isolated in 94% yield as a single diastereoisomer. Destructive template removal, by catalytic hydrogenation, released (5)-( )-cucurbitine, after ion-exchange chromatography, as the free amino acid in 90% yield (Scheme 3.46). 

C, and the excess hydride killed by the addition of 1.0 mL EtOAc, followed by 2.3 mL H20. The reaction mixture was filtered free of solids under a N2 atmosphere, washed with THF, and the filtrate and washings combined and stripped of solvent under vacuum. The residue was distilled in a KugelRohr apparatus and the solid distillate recrystallized from /hexane to give 0.24 g (52%) 3-[2-(diethylamino)ethyl]-4-indolol (4-HO-DET) as white crystals with a mp of 103-104 °C. The product discolored quickly in the presence of air, and was best stored under an inert atmosphere at -30 °C. Conversion to the phosphate ester was achieved by reaction of the sodium salt of 3-[2-(diethylamino)ethyl]-4-indolol with dibenzylchlorophosphonate, followed by the reductive removal of the benzyl groups with catalytic hydrogenation, as described for psilocybin. 

Surface-catalyzed dark and photoassisted phosphate ester hydrolysis (P—O bond rupture) in aqueous suspensions of TiO2 has been proposed [6,7,41]. A number of products indicative of radical cationic pathways have been reported in the TiO2 photocatalysis of benzyl phosphonic acid [44]. 

The cyclic phosphonate may be intercepted with hydroxylamine to yield the corresponding hydroxamate. Importantly, the rate of hydroxylaminolysis is approximately the same as ethanol loss, thus it appears that the cyclic phosphonate and not a precursor pentacovalent species is being trapped. Insofar as the analogy is appropriate, hydroxylamine is trapping an acyclic acyl phosphate in the above case, albeit at a rate faster than benzyl alcohol loss. It is also noteworthy that for both the phosphonate and phosphate esters there is no net transfer of oxygen from the carboxyl to phosphorus during the entire course of hydrolysis, i.e. loss of two moles of alcohol. 

The 4 -monophosphate was also prepared from the same compound as above (Figure 5). Although the 4 -hydroxyl group in 12 has rather low reactivity, its phosphorylation could be performed with phenyl phosphate and dicyclohexylcarbodiimide (DCC) in pyridine. The reaction product was converted into the benzyl phenyl ester ( ) to facilitate purification. In contrast to the above dibenzyl ester of the glycosyl phosphate, the benzyl phenyl ester of the 4 -phosphate was stable and could be purified by silica gel column chromatography after removal of the propenyl group without decomposition. Hydrogenolytic deprotection of (first with Pd-black then with PtC>2) afforded the 4 -monophosphate 17. 

Introduction of a phosphate monoester and removal of its protecting groups was a serious impediment in a synthesis of the serine-threonine phosphatase inhibitor Calyculin A by Evans and co-workers [Scheme 7,22].38 The four phosphate protecting groups evaluated were 2-cyanoethyl and 2-(trimethylsi]y])ethyl (see below), benzyl and p-methoxybenzyl. Of these, the p-methoxybenzyl phosphate ester offered the best compromise between base stability (it survived a Wittig reaction in the presence of a metal amide base) and acid lability required for the final deprotection step in which three secondary terf-butyldimethylsiiyl... 

SYNS 2-CHLORO-l-(2,4,5-TRICHLOROPHENYI.)VINYL DIMETHYL PHOSPHATE 2-CHLORO-l-(2,4,5-TRICHLOROPHENYL)VINYL PHOSPHORIC ACID DIMETHYL ESTER 0,0-DIMETHYL-0-2-CHL0R-l-(2,4,5-TRICHLORPHENYL)-VINYDPHOSPHAT (GERMAN) IPO 8 NCI-C00168 PHOSPHORIC ACID, 2-CHLORO-1 -(2,4,5-TRICHLOROPHENYL)ETHENYL DIMETHYL ESTER 2,4,5-TRICHLORO-a-(CHLOROMETHYLENE)-BENZYL PHOSPHATE... 

C10H15NO N-hydroxyethyl-a-methyl benzyl amine 1331-41-5 515.82 45.406 2 20390 C10H16NO4P DL-ephedrine phosphate (ester) 7234-09-5 601.15 53.683 1.2... 

A comparison of the effect of the structure of phosphate esters on uranium extraction from nitrate media shows that the esters from secondary alcohols give higher uranium distribution coefficients (D s) than those from primary alcohols, phenyl esters extract uranium less strongly than alkyl esters, and benzyl esters are intermediate in extractant strength for uranium (24). 

TFA, FDT, TIS, H2O. These conditions readily cleave the benzyl phosphate but also result in some methyl ester hydrolysis of a cyclic peptide. The problem was avoided by using hydrogenolysis to affect cleavage, but this also reduced an olefin in the molecule. 

The t-butyl ethers (210) are the major products of photolysis of the phosphate esters (211) in t-butanola benzyl cation-phosphate ion pair is thought to be involved in this conversion. In contrast, initial carbon-phosphorus bond cleavage is responsible... 

The photochemistry of phosphate esters, including benzylic phosphates, has recently been reviewed by Givens and Kueper [121]. Much of this research has... 

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