- Biomimetically activated amino acids. Catalysis in the hydrolysis of alanyl ethyl phosphate
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Alanyl ethyl phosphate (1) is an activated derivative of alanine that is functionally related to the corresponding aminoacyl adenylate, the initial activated amino acid intermediate in protein biosynthesis. To establish the inherent reactivity of these species, the kinetic parameters for hydrolysis of alanyl ethyl phosphate in water at 25 °C were determined. There is catalysis by acid (k = 4 x 10-4 M-1s-1) and base (k = 1.7 M-1 s-1) along with two pH-independent processes (k = 3 x 10-5 and 1.6 x 10-3 s- 1) that are connected as a kinetic titration curve of the amino group of alanyl ethyl phosphate (pK(a) = 7.8). The results are consistent with mechanisms proceeding via addition to the carbonyl of water or hydroxide with proton migrations. Reaction with methanol is slower than reactions with water while reaction with 2-propanol leads to complex products. In solutions sufficiently concentrated for 31P NMR analysis, alanyl ethyl phosphate also undergoes reactions that produce alanylalanine and other condensation products. Metal ions catalyze the hydrolysis reactions through complex formation. Cupric and zinc ions are most effective (~100-fold larger rate constant than water: association constants > 100 M-1) with magnesium and calcium forming weaker and less reactive complexes. These results show that aminoacyl alkyl phosphates are sufficiently stable to be used in water and that metal ions can facilitate their reactions. Improved catalysts will be needed to facilitate biomimetic processes such as aminoacylation of t-RNA.
- Kluger, Ronald,Loo, Richard W.,Mazza, Vince
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- 1996 Bader Award Lecture Aminoacyl ethyl phosphates. Biomimetically activated amino acids
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Aminoacyl ethyl phosphates are functional analogues of aminoacyl adenylates, the activated intermediates formed by ribosomal enzymes from the reaction of amino acids with ATP. The aminoacyl ethyl phosphates are prepared by DCC-mediated coupling of a tetraalkylammonium salt of ethyl phosphate and an N-t-Boc-amino acid, followed by deprotection. The efficiency of the synthesis and the solubility properties of the product depend on the alkyl group in the ammonium counterion of the phosphate. N-Protected and free aminoacyl ethyl phosphates hydrolyze slowly (t1/2 in neutral solution, 25°C, ～ 100 h). These materials are potentially useful in biomimetic peptide synthesis, protein modification, and aminoacylation of RNA.
- Kluger, Ronald,Li, Xianfeng,Loo, Richard W.
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- A convenient method for phosphorylation involving a facile oxidation of H-Phosphonate monoesters via bis(trimethylsilyl) phosphites
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A new convenient route to phosphate monoesters from alcohols has been developed. H-Phosphonate monoesters, which are readily accessible by phosphonylation of the parent alcohols, were oxidized with t-BuOOH or N- sulfonyloxaziridines under anhydrous conditions via the corresponding bis(trimethylsilyl) phosphites. N,O-Bis(trimethylsilyl)benzamide (BSB) and (camphorsulfonyl)oxaziridine (CSO) were found to be highly effective for silylation of H-phosphonates arid oxidation of silyl phosphites, respectively.
- Wada, Takeshi,Mochizuki, Akira,Sato, Yuichi,Sekine, Mitsuo
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- Pathways for the Reactions Between Neurotoxic Organophosphorus Compounds and Oximes or Hydroxamic Acids
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To obtain mechanistic insight into the recently demonstrated detoxification ability of β-cyclodextrin derivatives containing substituents with oxime or hydroxamic acid residues, analogous glucose derivatives with the same substituents were treated with cyclosarin (GF), tabun (GA), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) in (Tris)-HCl buffer (0.1 m, pH 7.40), and the different reaction pathways were studied by31P NMR spectroscopy and mass spectrometry. Consistent with previous reports, the oxime is phosphonylated by GF, which is followed by elimination of O-cyclohexyl methylphosphonate to afford a nitrile. Reaction of the hydroxamic acid with GA depends on whether the nitrogen atom of the hydroxamic acid bears a substituent or not. The unsubstituted hydroxamic acid affords a stable phosphate ester lacking the cyanide and the dimethylamino group of GA. If the hydroxamic acid is methylated, the initially formed phosphorylated product undergoes a number of transformations, including cleavage of the C–N bond of the hydroxamic acid. Reaction of the hydroxamic acid with VX involves a Lossen rearrangement. These investigations thus show that all investigated nucleophiles are irreversibly modified upon reaction with nerve agents under the chosen conditions, which indicates that cyclodextrins with oximes or hydroxamic acid as substituents are unlikely to afford catalytic nerve-agent scavengers.
- Bierwisch, Anne,Koller, Marianne,Worek, Franz,Kubik, Stefan
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- METHOD FOR PRODUCING PHOSPHOESTER COMPOUND
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PROBLEM TO BE SOLVED: To provide a method whereby, a phosphate compound selected from the group consisting of orthophosphoric acid, phosphonic acid, phosphinic acid, and anhydrides of them is used as raw material and, by one stage reaction, a corresponding phosphoester compound is produced. SOLUTION: To an aqueous solution of a phosphate compound, added is an organic silane or siloxane compound having an alkoxy group or an aryloxy group, and the mixture is subjected to a heating reaction, thereby producing a corresponding phosphoester compound without requiring a catalyst. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPOandINPIT
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Paragraph 0023-0028
(2021/09/27)
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- Wet and dry processes for the selective transformation of phosphonates to phosphonic acids catalyzed by br?nsted acids
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A "wet"process and two "dry"processes for converting phosphonate esters to phosphonic acids catalyzed by a Bronsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process). Thus, the conversion of dibenzyl phosphonates to the corresponding phosphonic acids took place smoothly at 80 °C in toluene or benzene in high yields. Moreover, selective conversion of benzyl phosphonates RP(O)(OR′)(OBn) to the corresponding mono phosphonic acids RP(O)(OR′)(OH) can also be achieved under the reaction conditions. The dealkylation via the generation of isobutene of ditert- butyl phosphonate, and the related catalysis by TfOH took place even at room temperature to give the corresponding phosphonic acids in good to high yields. Nafion also shows high catalytic activity for these reactions. By using Nafion as the catalyst, phosphonic acids could be easily prepared on a large scale via a simple process.
- Li, Chunya,Saga, Yuta,Onozawa, Shun-Ya,Kobayashi, Shu,Sato, Kazuhiko,Fukaya, Norihisa,Han, Li-Biao
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p. 14411 - 14419
(2020/12/29)
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- 31PNMR study on the reactions of amino acids and sugar derivatives with pyrophosphorous acid as a possible prebiotic phosphonylating agent
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Phosphorus is an essential element in living organisms. Evaluating prebiotic processes that lead to phosphorylated biomolecules is an important step toward understanding the origin of life. Schreibersite ([Fe,Ni]3P) is a meteoritic phosphorus mineral which releases various phosphorus species reactive toward biomolecules. We studied the reactions between biomolecules and pyrophosphorus acid (H4P2O5), which is a phosphorous acid derivative released from schreibersite. The reactions between pyrophosphorous acid and molecules having hydroxy groups were carried out under mild alkaline conditions. Notably, some biologically important molecules such as L-serine, L-tyrosine, L-threonine, D-ribose, and D-glyceraldehyde reacted with pyrophosphorous acid to give corresponding phosphonates. These results suggested that if schreibersite and the biomolecules co-existed in the prebiotic earth, they formed the phosphonates which were able to play roles as surrogates or precursors of phosphorylated biomolecules.
- Seio, Kohji,Shiozawa, Takashi,Sugiyama, Daiki,Ohno, Kentaro,Tomori, Takahito,Masaki, Yoshiaki
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p. 905 - 911
(2019/05/21)
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- An Unusual Two-Step Hydrolysis of Nerve Agents by a Nanozyme
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Organophosphate-based nerve agents irreversibly inhibit acetylcholinesterase enzyme, leading to respiratory failure, paralysis and death. Several organophosphorus hydrolases are capable of degrading nerve agents including pesticides and insecticides. Development of stable artificial enzymes capable of hydrolysing nerve agents is important for the degradation of environmentally toxic organophosphates. Herein, we describe a Zr-incorporated CeO2 nanocatalyst that can be used for an efficient capture and hydrolysis of nerve agents such as methyl paraoxon to less toxic monoesters. This unusual sequential degradation pathway involves a covalently linked nanocatalyst-phosphodiester intermediate.
- Khulbe, Kritika,Roy, Punarbasu,Radhakrishnan, Anusree,Mugesh, Govindasamy
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p. 4840 - 4845
(2018/09/27)
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- Intriguing structural chemistry of neutral and anionic layered monoalkylphosphates: Single-source precursors for high-yield ceramic phosphates
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Building up on an available synthetic methodology, phosphate monoesters ROPO3H2 have been synthesized in good yields. The synthetic procedure employed features acetic anhydride mediated activation of phosphoric acid in the presence of alcohols, leading to the formation of phosphate monoesters. The products have been isolated as their cyclohexyl amine salts, [CyNH3]2[(MeO)PO3]·3H2O (1) and [CyNH3][(RO)PO3H] (Cy = cyclohexyl; R = Et (2), iPr (3), or tBu (4)). Neutralization of 1-4 by readily available inexpensive ion exchange resin Amberlite produces monoalkylphosphates (RO)P(O)(OH)2 (R = Me (5), Et (6), iPr (7), or tBu (8)). Thermally labile 1-4 and 7 have been structurally characterized by single crystal X-ray diffraction studies. Due to their intrinsic thermal instability due to β-H elimination, these compounds can be used as ligands for the preparation of single-source precursors for ceramic phosphates by reacting them with suitable metals ions. It is also possible to isolate co-crystals of the anionic and neutral forms of these phosphates as it has been demonstrated in the isolation and structural characterization of [(iPrO)PO3H2]·{[CyNH3][(iPrO)PO3H]} (9). To demonstrate the utility of these monoalkylphosphates in the low-temperature synthesis of metal phosphate bioceramics, isopropyl phosphate 7 has been employed to prepare calcium phosphate [{Ca((iPrO)PO3)(OH2)}·H2O]n (10), which undergoes neat thermal decomposition in two stages to lose water and propene to yield β-Ca2P2O7 at low temperatures (280 °C).
- Bhat, Gulzar A.,Kalita, Alok Ch.,Murugavel, Ramaswamy
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p. 5390 - 5401
(2017/09/26)
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- Human P2Y14 receptor agonists: Truncation of the hexose moiety of uridine-5′-diphosphoglucose and its replacement with alkyl and aryl groups
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Uridine-5′-diphosphoglucose (UDPG) activates the P2Y14 receptor, a neuroimmune system GPCR. P2Y14 receptor tolerates glucose substitution with small alkyl or aryl groups or its truncation to uridine 5′-diphosphate (UDP), a full agonist at the human P2Y14 receptor expressed in HEK-293 cells. 2-Thiouracil derivatives displayed selectivity for activation of the human P2Y14 vs the P2Y6 receptor, such as 2-thio-UDP 4 (EC50=1.92 nMat P2Y14, 224-fold selectivity vs P2Y6) and its β-propyloxy ester 18. EC50 values of the β-methyl ester of UDP and its 2-thio analogue were 2730 and 56 nM, respectively. β-tert-Butyl ester of 4 was 11-fold more potent than UDPG, but β-aryloxy or larger, branched β-alkyl esters, such as cyclohexyl, were less potent. Ribose replacement of UDP with a rigid North or South methanocarba (bicyclo[3.1.0]hexane) group abolished P2Y14 receptor agonist activity. α,β-Methylene and difluoromethylene groups were well tolerated at the P2Y14 receptor and are expected to provide enhanced stability in biological systems. α,β-Methylene-2-thio-UDP 11 (EC50 = 0.92 nM) was 2160-fold selective versus P2Y6. Thus, these nucleotides and their congeners may serve as important pharmacological probes for the detection and characterization of the P2Y14 receptor.
- Das, Arijit,Ko, Hyojin,Burianek, Lauren E.,Barrett, Matthew O.,Harden, T. Kendall,Jacobson, Kenneth A.
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scheme or table
p. 471 - 480
(2010/05/02)
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- Mono, di and tri-mannopyranosyl phosphates as mannose-1-phosphate prodrugs for potential CDG-Ia therapy
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An efficient and convergent method for the synthesis of mannose-1-phosphate prodrugs is described as a potential therapy for congenital disorders of glycosylation-Ia (CDG-Ia). The key feature of the proposed approach is the silver assisted nucleophilic substitution of 2,3,4,6-tetra-O-protected-α-d-mannopyranosyl bromides with various silver phosphate salts to afford mono, di, and tri-mannopyranosyl phosphates. A preliminary biological evaluation of the synthesized phosphate prodrugs has been carried out.
- Hardre, Renaud,Khaled, Amira,Willemetz, Alexandra,Dupre, Thierry,Moore, Stuart,Gravier-Pelletier, Christine,Merrer, Yves Le
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p. 152 - 155
(2007/10/03)
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- Biomimetic aminoacylation of ribonucleotides and RNA with aminoacyl phosphate esters and lanthanum salts
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Aminoacylation of tRNA in cells involves activation of the amino acid as an aminoacyl adenylate, a mixed anhydride with AMP, which reacts with tRNA. We have now established that aminoacyl phosphate esters in the presence of lanthanide ions in water will acylate hydroxyls at the 3′-terminus of RNA or a simple nucleotide. By extension, this will permit synthetically aminoacylated tRNA to be produced in a single-step biomimetic process. The reactions of Boc-4-fluorophenylalanyl ethyl phosphate were followed by HPLC separation, MS, and 19F NMR analysis. In stoichiometric combination with lanthanum salts in aqueous buffer, Boc-4-fluorophenylalanyl ethyl phosphate rapidly produces 2′- and 3′-monoesters of cytidine and cytidine monophosphate. Reaction of the reagent with RNA in the presence of lanthanum and magnesium salts introduces a specifically detectable signal into the RNA, which is evidence of formation of the aminoacyl ester. When the same RNA is initially oxidized with periodate to convert the 3′-terminal vicinal diol to the cleaved dialdehyde, reaction with the aminoacyl phosphate no longer occurs as evidenced by the lack of a signal in the 19F NMR spectrum. The results are consistent with a requisite chelation mechanism in which lanthanum serves as a template for both the aminoacyl phosphate and the 3′-terminal diol of RNA and nucleotides. The coordinated diol will then react through specific base-catalyzed intramolecular addition of the alkoxide nucleophile to the acyl group of the aminoacyl phosphate. Assessment of the method with a single tRNA was also achieved using the fluorescent reagent N-dansyl-glycyl ethyl phosphate. Lanthanide-promoted aminoacylation at the 3′-terminus of tRNAPhe is detected by the introduction of fluorescence (detected directly and by antibody-enhanced emission). This does not occur if the 3′-terminus is converted to the dialdehyde by reaction with periodate.
- Tzvetkova, Svetlana,Kluger, Ronald
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p. 15848 - 15854
(2008/09/19)
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- Regioselective phosphorylation of carbohydrates and various alcohols by bacterial acid phosphatases; probing the substrate specificity of the enzyme from Shigella flexneri
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Bacterial non-specific acid phosphatases normally catalyze the dephosphorylation of a variety of substrates. As shown previously the enzymes from Shigella flexneri and Salmonella enterica are also able to catalyze the phosphorylation of inosine to inosine monophosphate and D-glucose to D-glucose 6-phosphate (D-G6P) using cheap pyrophosphate as the phosphate donor. After optimization high yields (95%) are achieved in the latter reaction and we show here that it is possible to use these enzymes in a preparative manner. This prompted us to investigate by using 31P NMR and HPLC also the phosphorylation of a broad range of carbohydrates and alcohols. Many cyclic carbohydrates are phosphorylated in a regioselective manner. Non-cyclic carbohydrates are phosphorylated as well. Phosphorylation of linear alcohols, cyclic and aromatic alcohols is also possible. In all cases the acid phosphatase from Shigella prefers a primary alcohol function above a secondary one. We conclude that these enzymes are an attractive alternative to existing chemical and enzymatic methods in the phosphorylation of a broad range of compounds.
- Van Herk, Teunie,Hartog, Aloysius F.,Van Der Burg, Alida M.,Wever, Ron
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p. 1155 - 1162
(2007/10/03)
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- Synthesis of Trialkyl Phosphates from White Phosphorus
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A new method was proposed for preparing trialkyl phosphates directly from white phosphorus by its electrolysis in a mixture of acetonitrile, alcohol, and water with tetraethylammonium iodide as supporting electrolyte. To increase the amount of the product synthesized in the unit volume of the electrolyte solution and the productivity of the process, phosphorus and water are added to the electrolyte in portions, which allows synthesis of up to 1 mol of trialkyl phosphate in 1 1 of the electrolyte solution.
- Romakhin,Nikitin
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p. 1023 - 1026
(2007/10/03)
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- Efficient catalytic phosphate diester cleavage by the synergetic action of two Cu(II) centers in a dinuclear cis-diaqua Cu(II) calix[4larene enzyme model
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A calix[4]arene derivative 2-[Cu(II)]2 functionalized with two cis-diaqua Cu(II) centers at the distal positions of the upper rim was synthesized and investigated as a model for dinuclear metalloenzymes that catalyze chemical transformations of
- Molenveld, Peter,Engbersen, Johan F. J.,Kooijman, Huub,Spek, Anthony L.,Reinhoudt, David N.
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p. 6726 - 6737
(2007/10/03)
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- Aryl H-phosphonates. 7. Studies on the formation of phosphorus-carbon bond in the reaction of trityl and benzyl halides with dialkyl and diphenyl H-phosphonates
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The reactions of H-phosphonate diesters with trityl and benzyl halides were investigated using 31P NMR spectroscopy. It was found that extensive oxidation, which usually accompanies the formation of trityl- or p-nitrobenzylphosphonates from the corresponding alkyl bromides in the Michaelis-Becker reaction, can be considerably suppressed or completely eliminated by reacting p-nitrobenzyl or trityl bromides with diphenyl H-phosphonate in acetonitrile in the presence of DBU.
- Kers, Annika,Stawinski, Jacek,Dembkowski, Leszek,Kraszewski, Adam
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p. 12691 - 12698
(2007/10/03)
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- Synthetic ribofuranose-containing polymers show catalytic activity in the hydrolysis of phosphodiesters
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Synthetic polymers containing ribofuranose rings as pendent groups catalyse the cleavage of DNA and the hydrolysis of phosphodiesters with a rate acceleration of 103 compared with that of the uncatalysed reactions.
- Han, Man Jung,Yoo, Kyung Soo,Cho, Tae Joon,Chang, Ji Young,Cha, Yu Jin,Nam, Seok Hyun
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p. 163 - 164
(2007/10/03)
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- Etude par RMN du 31P de l'hydrolyse des esters phosphoriques
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Silicated and phosphates exhibit similar structures based on corner sharing and tetrahedra.However their solution chemistry is very different and the sol-gel synthesis of phosphate materials is rather difficult whereas the sol-gel synthesis of silicates has been extensively studied.It is based on the hydrolysis and condensation of silicon alkoxides Si(OR)4.These reactions can be described as SN2 nucleophilic substitutions.The sensitivity of alkoxides toward hydrolysis then depends on the electronegativity of the central atom and its ability to increase its coordination number.As a result phosphoric esters PO(OR)3 are very difficult to hydrolyse under ambient conditions.This paper shows that PO(OEt)3 can be hydrolyzed upon heating under reflux in the presence of sulfuric acid.Various PO(OEt)3-x(OH)x (0 /= x /= 3) species are formed.They are quantitatively characterized by 31P NMR.The position of bond scission during hydrolysis is of key importance.Sulfuric acid tends to favor the dissociation of the O-C bond rather than the P-O bond leading to the formation of P-OH groups.Mono and di-esters (x = 1 or 2) should be better precursors than PO(OR)3 or PO(OH)3 for the sol-gel synthesis of phosphate materials.
- Vandenborre, M. T.,Maquet, J.,Livage, J.
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p. 329 - 340
(2007/10/02)
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- PHOTOLYSIS OF ARYL ESTERS OF TRI- AND TETRACOORDINATED PHOSPHORUS COMPOUNDS
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Upon UV excitation in methanol, some diaryl esters of alkly- or alkenyl phosphonates underwent an elimination of two aryl groups to give biaryls and the corresponding alkyl- or alkenylphosphonic acids.Tris(4-methoxyphenyl) phosphite also underwent a similar elimination to give 4,4'-dimethoxybiphenyl and 4-methoxyphenyl phosphonate.This interesting biaryl elimination was confirmed to proceed via a singlet intramolecular excimer by means of fluorescence spectra and Stern-Volmer analysis.
- Shi, Min,Yamamoto, Kiichi,Okamoto, Yoshiki,Takamuku, Setsuo
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- CONVENIENT SYNTHETIC ROUTE TO MONO- OR DIAKLYL PHOSPHATE FROM INORGANIC PHOSPHORUS ACIDS
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Mono- or dialkyl phosphate was synthesized in a favorable yield by oxidation of phosphonic or phosphinic acid in alcohol with oxygen at the presence of a catalytic amount of copper(II)chloride.The reaction may proceed via the formation of corresponding phosphorochloridate or phosphorochloridite.
- Okamoto, Yoshiki,Kusano, Tetuya,Takamuku, Setsuo
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p. 195 - 200
(2007/10/02)
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- Microbiocidal cleansing and disinfecting formulations and preparation thereof
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A cleansing or disinfecting solution that includes an effective amount of a salt of phosphoric acid or its ester of the formula: STR1 wherein R is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and neopentyl and X is selected from the group consisting of Group IA metals, Group IIA metals, transition metals, and HNR1 R2 R3+, wherein R1 and R2 are alkyl groups of from 4 to 18 carbon atoms or a hydroxyalkyl group of 1 to 18 carbon atoms, and R3 is an alkyl group of from 8 to 18 carbon atoms, and wherein when R is hydrogen, X is di-(2-hydroxyethyl)cocoamine. These formulations are effective in killing or inhibiting a wide variety of harmful, destructive or offensive microorganisms including viruses, bacteria, yeasts, algae and molds.
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- Reaction of Epoxides with Metaphosphoric Acid Derivatives
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Ethyl metaphosphate (EtOPO2), eliminated in the thermolysis of the bridged cyclic phosphonate endo-3-ethoxy-6-methyl-N-phenyl-2,3-oxabicyclooct-5-ene-8,9-dicarboximide 3-oxide, has been found to cause ring opening of epoxides, resulting in formation of 2-ethoxy-4-substituted 1,3,2-dioxaphospholane 2-oxides as major products.N,N-Diethyl metaphosphoramidate (Et2NPO2) reacted similarly.With ethyl metathiophosphate (EtOP(S)O), the 1,3,2-oxathiaphospholane 2-oxide ring was formed.Products of these reactions were characterized by 31P NMR spectroscopy and by GC-MS.These reactions are presumed to be initiated by electrophilic attack of the metaphosphate on the epoxide oxygen to form a cyclic oxonium ion.
- Bodalski, Ryszard,Quin, Louis D.
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p. 2666 - 2671
(2007/10/02)
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- Phosphorous-31 Nuclear Magnetic Resonance Study of the Mechanism and Kinetics of the Hydrolysis of Zinc(II) O,O-Diethyl Dithiophosphate and Some Related Compounds
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31P NMR spectroscopy has been used to investigate the mechanism and kinetics of hydrolysis of Zinc(II) O,O-diethyl dithiophosphate (1) (ZDTP) in 1,2-dimethoxyethane solution at 85 deg C with ten equivalents of water.All major intermediates and products have been identified and the individual reaction rates determined.ZDTP was found to be hydrolyzed (k=2.35 x 10-4 s-1) to phosphoric acid (7) via O,O-diethyl S-hydrogen dithiophosphate (3) (khyd=1.35 x 10-2 s-1) and thiophosphoric acid (6) (khyd=0.78 x 10-5 s-1).O-Ethyl O,O-dihydrogen and O,O-diethyl-O-hydrogen phosphorothioates (8), (9), and ethyl dihydrogen phosphate (10) were produced as by-products of the reaction.From a study of the order of appearance of the intermediates and products, a detailed mechanism for the hydrolysis of ZDTP has been proposed.O-Ethyl O,S-dihydrogen phosphorothioate (4) and dithiophosphoric acid (5) are found to be intermediates.
- Burn, Alan J.,Dewan, Sharwan K.,Gosney, Ian,Tan, Paul S. G.
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p. 753 - 758
(2007/10/02)
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- The Selective Dealkylation of Mixed Esters of Phosphoric Acid and Phenylphosphonic Acid Using Cation Exchange Resin
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Cation exchange resin (SO3H) is a highly selective dealkylation reagent for mixed esters of phosphorus oxyacids bearing primary and secondary alkyl groups.The desired products which were produced by dealkylation of the secondary alkyl group were obtained in high yields under anhydrous and mild conditions.Keywords - dealkylation; cation exchange resin; carbonium ion; phosphorus oxyacid ester; trialkyl phosphate; dialkyl phenylphosphonate; p-toluenesulfonic acid
- Nitta, Yoshihiro,Arakawa, Yasushi
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p. 3121 - 3129
(2007/10/02)
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- Photochemical Carbon-Phosphorus Bond Cleavage of Nitro-substituted Benzylphosphonic Acids
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Upon u.v.-irradiation, the C-P bond of p-nitrobenzylphosphonate is more readily cleaved to give a monomeric metaphosphate anion as intermediate than those of o- and m-derivatives.
- Okamoto, Yoshiki,Iwamoto, Narimasa,Takamuku, Setsuo
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p. 1516 - 1517
(2007/10/02)
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- Solvolysis of α-Arylvinyl Ethyl Phosphates in Aqueous and Methanolic Solutions: Intramolecular Participation by the oxy Group
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The α-arylvinyl ethyl phosphates 2a-c were synthesized and their solvolysis reactions were studied in acidic aqueous solution and methanol.In aqueous solution both the anionic and neutral diesters are subject to acid-catalyzed hydrolysis.Solvent deuterium isotope effects, the observation of general acid catalysis by formic acid, and comparison with the reaction characteristics of the acid-catalized hydrolysis of other vinyl esters and ethers indicate that the anionic diesters hydrolyze via an ASE2 mechanism.The ratio of the rate constants for hydronium ion catalyzed hydrolysis of anionic and protonated 2c, k-/k0, is 14.1 +/- 0.3.This modest acceleration is consistent with weak electrostatic stabilization of the developping cation by the anionic site, although an inductive effect must also contribute.A previously reported correlation of log kH+ for a series of alkenes of the type R1R2C=CH2 with the sum of the ?P+ parameters for R1 and R2 and k- for 2a at 25 deg C were used to calculate a value of -0.52 for the ?P+ parameter of the anionic oxy group.The estimated ?P+ of the protonated group is -0.43.These parameters and direct comparisons of hydrolysis rates of 2a-c with the hydrolysis rates of the corresponding triesters 1a-c and the α-arylvinyl methyl ethers confirm that the oxy group, in both of its ionization states, is intermediate between a oxy group and an alkoxy group in its ability to stabilize a cation.The solvolysis of 2a-c in methanol/HCl proceeds via two routes.An HCl-catalyzed pathway has characteristics very similar to the acid-catalyzed hydrolysis reactions.Another path, the rate of which is independent of HCl concentration, apparently involves intramolecular general acid catalysis of methanolysis by the prot onated oxy group.Differences in the ionization caonstants of the diesters in the two solvents apparently account for the divergent solvolysis behavior.
- Novak, Michael,Roy, Kalpana R.
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p. 4584 - 4590
(2007/10/02)
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- Phosphorylation with Pyrophosphoric Acid
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Dihydrogenphosphates of primary and secondary aliphatic alcohols as well as phenol were prepared by a very simple procedure with pyrophosphoric acid. t-Butyl and benzyl dihydrogenphosphates could be obtained by a slight modification of the reaction conditions.For the purpose of phosphorylation pyrophosphoric acid was more reactive than orthophosphoric acid.
- Yamaguchi, Hachiro,Ogura, Fumio,Otsubo, Tetsuo,Ikeura, Yasuhiro
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p. 1891 - 1892
(2007/10/02)
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- Properties and Reactions of Trimethyl Phosphite, Trimethyl Phosphate, Triethyl Phosphate, and Trimethyl Phosphorothionate by Ion Cyclotron Resonance Spectroscopy
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The gas-phase ion-molecule reactions occurring in trimethyl phosphite, trimethyl phosphate, triethyl phosphate, and trimethyl phosphorothionate have been investigated by ion cyclotron resonance spectroscopy.Protonated parent ions, tetracoordinated phosphonium ions, and cluster ions are the reaction products observed.The proton affinities of these compounds have been determined to be 222.9, 214.2, 218.7, and 216.6 kcal/mol, respectively (relative to PA(NH3) = 207.0 kcal/mol).Homolytic bond dissociation energies of the protonated species are calculated using adiabatic ionization potentials determined by photoelectron spectroscopy.The trends in these quantities are discussed.A reasonable value for the correlated homolytic bond dissociation energy of trimethyl phosphite indicates that the first ionization potential of this molecule should be assigned to the phosphorus lone pair.The application of chemical ionization mass spectrometry to the analysis of phosphorus esters is briefly discussed.
- Hodges, Ronald V.,McDonnell, T. J.,Beauchamp, J. L.
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p. 1327 - 1332
(2007/10/02)
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