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Transalkylation of phosphotriesters using cob(I)alamin: Toward specific determination of DNA-phosphate adducts
The supernucleophilic cobalt compound, cob(I)alamin, has been kinetically characterized with respect to its ability to bring about transalkylation of adducts to DNA phosphates (phosphotriesters). The reactivity of cob(I)alamin toward different phosphotrie
Haglund, Johanna,Rafiq, Adnan,Ehrenberg, Lars,Golding, Bernard T.,Toernqvist, Margareta
p. 253 - 256
(2000)
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Investigations on diazo compounds and azides- LXII.1 1 Part LXI: H. Heydt, P. Eisenbarth, K. Feith and M. Regitz, J. Heterocycl. Chem., 22, (1985), in press. Synthesis and reactions of a-diazo phosphonates with a conjugated 1,3-diene unit
α-Diazo phosphonates with a conjugated 1,3-diene unit are synthesised by the Bamford-Stevens reaction (2 →4→3). They undergo [4+2]-cycloadditions with the dienophile 5 to form the tetrahydrotriazolopyridazines 8, which possess an unchanged diazo group. In contrast, dimethyl acetylenedicarboxylate (9) reacts exclusively with the diazo dipole of 3 to yield the 3H-pyrazoles 10, which rearrange to 11 by sigmatropic PO-shifts and hydrolyse to form 13. The diazo compound 3b isomerises to the pyrazole 16 when heated in benzene.
Theis, Wolfgang,Regitz, Manfred
p. 2625 - 2634
(1985)
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Gas-phase reaction of dichlorvos, carbaryl, chlordimeform, and 2,4-D butyl ester with OH radicals
Widespread use of pesticides has caused serious environmental concern. In order to evaluate the fate of organic pesticides in the atmosphere, rate constants for gas phase reactions of OH radicals with dichlorvos, carbaryl, chlordimeform, and 2,4-D butyl ester were measured using the relative rate method at ambient temperature and 101 kPa total pressure. On-line FTIR spectroscopy was used to monitor the concentrations of pesticides as a function of time. The reaction rate constants with OH radicals (in units of cm 3 molecule-1 s-1) have been determined as (2.0±0.4) × 10-11 for dichlorvos, (3.3±0.5) × 10-11 for carbaryl, (3.0±0.7) × 10 -10 for chlordimeform, and (1.5 ± 0.2) × 10 -11 for 2,4-D butyl ester. These rate constants agree well with those estimated based on the structure-activity relationship. The group rate constant for N=C group (k(N=c)) was estimated as 2.7 × 10-10 cm3 molecule-1 s-1. Dimethyl phosphite has been tentatively identified as a product of the reaction of dichlorvos with OH radicals. Atmospheric lifetimes due to the reactions with OH radicals were also estimated (in units of h): 14±3 for dichlorvos, 8±1 for carbaryl, 1.0±0.3 for chlordimeform, and 19±3 for 2,4-D butyl ester. These short atmospheric lifetimes indicate that the four organic pesticides degrade rapidly in the atmosphere, and they themselves are unlikely to cause persistent pollution. Further studies are needed to identify the potential hazard of their degradation products.
Sun,Zhu,Shang,Han
p. 755 - 762
(2005)
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Buffer-Induced Acceleration and Inhibition in Polyoxometalate-Catalyzed Organophosphorus Ester Hydrolysis
The Zr-containing polyoxometalates (POMs), including (Et2NH2)8{[α-PW11O39Zr(μ-OH)(H2O)]2}·7H2O (1), effectively catalyze the hydrolysis of nerve agent simulants at near-neutral pH. Analogous Zr-containing heterogeneous systems are much-studied and effective nerve-agent hydrolysis catalysts, but due to their heterogeneous nature, it is very challenging to know the exact structure of the catalytic sites during turnover and to clarify at the molecular level the elementary mechanistic processes. Here, under homogeneous conditions, hydrolysis rates of the nerve-agent simulant methyl paraoxon catalyzed by 1 are examined as a function of pH, ionic strength, catalyst, and substrate concentrations. In addition, the specific effect of three commonly used buffers is examined, revealing that acetate functions as a co-catalyst, phosphate inhibits hydrolytic activity, and 2-(N-morpholino)ethanesulfonic acid (MES) has no effect on the hydrolysis rate. Spectroscopic (31P nuclear magnetic resonance) and computational studies demonstrate how each of these buffers interacts with the catalyst and offer explanations of their impacts on the hydrolysis rates. The impact of the nerve-agent hydrolysis product, methyl phosphonic acid, is also examined, and it is shown to inhibit hydrolysis. These results will aid in the design of future Zr-based hydrolysis catalysts.
Collins-Wildman, Daniel L.,Kim, Mooeung,Sullivan, Kevin P.,Plonka, Anna M.,Frenkel, Anatoly I.,Musaev, Djamaladdin G.,Hill, Craig L.
p. 7068 - 7076
(2018)
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Atmospheric chemistry of dichlorvos
Dichlorvos [2,2-dichlorovinyl dimethyl phosphate, (CH3O) 2P(O)OCH=CCl2] is a relatively volatile in-use insecticide. Rate constants for its reaction with OH radicals have been measured over the temperature range 296-348 K and atmospheric pressure of air using a relative rate method. The rate expression obtained was 3.53×10 -13 e(1367±239)/T cm3 molecule -1 s-1, with a 298 K rate constant of (3.5 ± 0.7)×10-11 cm3 molecule-1 s-1, where the error in the 298 K rate constant is the estimated overall uncertainty. In addition, rate constants for the reactions of NO3 radicals and O3 with dichlorvos, of (2.5 ± 0.5)×10 -13 cm3 molecule-1 s-1 and (1.7 ± 1.0)×10-19 cm3 molecule-1 s -1, respectively, were measured at 296 ± 2 K. Products of the OH and NO3 radical-initiated reactions were investigated using in situ atmospheric pressure ionization mass spectrometry (API-MS) and (OH radical reaction only) in situ Fourier transform infrared (FT-IR) spectroscopy. For the OH radical reaction, the major initial products were CO, phosgene [C(O)Cl 2] and dimethyl phosphate [(CH3O)2P(O)OH], with equal (to within ±10%) formation yields of CO and C(O)Cl2. The API-MS analyses were consistent with formation of (CH3O) 2P(O)OH from both the OH and NO3 radical-initiated reactions. In the atmosphere, the dominant chemical loss processes for dichlorvos will be daytime reaction with OH radicals and nighttime reaction with NO3 radicals, with an estimated lifetime of a few hours.
Aschmann, Sara M.,Tuazon, Ernesto C.,Long, William D.,Atkinson, Roger
p. 2756 - 2764
(2011)
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Tuning the Lewis acidity of metal-organic frameworks for enhanced catalysis
The kinetics of hydrolysis of dimethyl nitrophenyl phosphate (DMNP), a simulant of the nerve agent Soman, was studied and revealed transition metal salts as catalysts. The relative rates of DMNP hydrolysis by zirconium and hafnium chlorides are in accordance with their Lewis acidity.In situconversion of zirconium chloride to zirconium oxy-hydroxide was identified as the key step. We propose a precursor-MOF activity relationship.
Devulapalli, Venkata Swaroopa Datta,Richard, Mélissandre,Luo, Tian-Yi,De Souza, Mattheus L.,Rosi, Nathaniel L.,Borguet, Eric
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p. 3116 - 3120
(2021/03/16)

Defect Level and Particle Size Effects on the Hydrolysis of a Chemical Warfare Agent Simulant by UiO-66
Defect engineering in metal-organic frameworks (MOFs) has recently become an area of significant research due to the possibility of enhancing material properties such as internal surface area and catalytic activity while maintaining stable 3D structures. Through a modulator screening study, the model Zr4+ MOF, UiO-66, has been synthesized with control of particle sizes (100-1900 nm) and defect levels (2-24%). By relating these properties, two series were identified where one property remained constant, allowing for independent analysis of the defect level or particle size, which frequently change coincident with the modulator choice. The series were used to compare UiO-66 reactivity for the hydrolysis of a chemical warfare agent simulant, dimethyl 4-nitrophenylphosphate (DMNP). The rate of DMNP hydrolysis displayed high dependence on the external surface area, supporting a reaction dominated by surface interactions. Moderate to high concentrations of defects (14-24%) allow for the accessibility of some interior MOF nodes but do not substantially promote diffusion into the framework. Individual control of defect levels and particle sizes through modulator selection may provide useful materials for small molecular catalysis and provide a roadmap for similar engineering of other zirconium frameworks.
Bartlett, Eamon C.,Cai, Meng,Gibbons, Bradley,Johnson, Eric M.,Morris, Amanda J.,Yang, Xiaozhou
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p. 16378 - 16387
(2021/11/13)

METHOD FOR PRODUCING PHOSPHOESTER COMPOUND
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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(2021/09/27)

Insights into Catalytic Hydrolysis of Organophosphonates at M-OH Sites of Azolate-Based Metal Organic Frameworks
Organophosphorus nerve agents, a class of extremely toxic chemical warfare agents (CWAs), have remained a threat to humanity because of their continued use against civilian populations. To date, Zr(IV)-based metal organic framework (MOFs) are the most pre
Cao, Ran,Chen, Haoyuan,Farha, Omar K.,Islamoglu, Timur,Kirlikovali, Kent O.,Mian, Mohammad Rasel,Snurr, Randall Q.
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p. 9893 - 9900
(2021/07/19)

Scalable and hierarchically designed MOF fabrics by netting MOFs into nanofiber networks for high-performance solar-driven water purification
Integrating metal-organic frameworks (MOFs) into flexible polymeric matrices can improve their practical processability and expand industrial applications greatly. However, current methods suffer from the serious aggregation of MOFs, low MOF loading, sacrifice of inherent pores in MOFs, and limited tunability of both MOFs and matrices. Herein, a novel net-fishing inspired strategy is developed for scalable and rapid production of high-performance MOF fabrics with tailored hierarchical architectures. It simultaneously realizes the good dispersion of individual MOF particles embedded into fishnet-like pores and achieves a maximum MOF loading of 85.7 wt%, while maintaining the inherent pore structures of the MOFs and enabling the convenient regulation of the functionality of the porous nanofibrous supports. Furthermore, a MOF fabric with UiO-66-NH2particles and carbon nanotubes (CNTs) confined inside functionalized polyacrylonitrile (PAN) nanofiber scaffolds is presented for solar-driven production of potable water from chemical warfare agent (CWA) simulant sewage. As a result, a record-breaking half-life of dimethyl-4-nitrophenyl phosphate (DMNP) and a promising water generation rate (2.97 L m?2d?1) are achieved. Owing to the versatility, our strategy provides a pioneering and fascinating platform for the future design of MOF fabrics with wide practical applications.
Li, Ailin,Liu, Ye,Qin, Xiaohong,Wang, Liming,Xiong, Jian,Yu, Jianyong
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p. 21005 - 21012
(2021/10/05)

Combining Two into One: A Dual-Function H5PV2Mo10O40?MOF-808 Composite as a Versatile Decontaminant for Sulfur Mustard and Soman
Due to the unpredictable nature of a battlefield environment, in the simultaneous degradation of sulfur mustard and nerve agents it is preferable to use just one decontaminant. Herein, the new composite HPVMo?MOF-808 (HPVMo = H5PV2Mo10O40) was deliberately synthesized via a simple impregnation method and thoroughly characterized. The results showed that the decontamination rate of the composites (30-40 mg) with optimal HPVMo loadings for HD (4 μL) and GD (4 μL) under ambient conditions was 97.2% (within 120 min) and 90.8% (within 30 min), respectively. Due to the combinational/synergistic effect of MOF-808 and encapsulated homogeneously dispersed HPVMo, the composite can very efficiently oxidize HD to nontoxic products in a single system, while retaining the inherent excellence of MOF-808 in hydrolytically degrading GD. The decontamination process was found to follow first-order reaction kinetics, and the rate constant and half-life of the composite for HD and GD were 0.0231 min-1, 30.13 min and 0.0795 min-1, 8.72 min, respectively. In addition, experimental results in guinea pigs and Kunming mice used as animal models showed that the composite provided effective skin protection against HD and GD, showing great potential for application in skin decontamination and protection.
Gao, Qi,Huang, Chengcheng,Liu, Jie,Wang, Yong'An,Yu, Jialin,Zhang, Lijuan,Zhong, Yuxu,Zhou, Yuanyuan,Zhou, Yunshan
(2020/08/24)

Catalytic degradation of an organophosphorus agent at Zn-OH sites in a metal-organic framework
Chemical warfare agents (CWAs), and in particular organophosphorus nerve agents, still pose a significant threat to society due to their continued use despite international bans. While nature has constructed a variety of enzymes that are capable of rapidly hydrolyzing organophosphorus substrates, the poor stability of enzymes outside of buffered solutions has limited their use in practical applications, such as in filters or on protective suits. As a result, we have explored the use of metal-organic frameworks (MOFs) as robust and tunable catalytic materials in which the nodes can be tailored to resemble the active sites found in these enzymes. We identified the Zn-based MOF, MFU-4l, as a promising hydrolysis catalyst due to the presence of Zn(II)-OH groups on the nodes, which are structurally reminiscent of the active sites in carbonic anhydrase (CA), a Zn-based enzyme that has been shown to efficiently catalyze the hydrolysis of phosphate esters. Indeed, MFU-4l can rapidly hydrolyze both the organophosphorus nerve agent, GD, and its simulant, DMNP, with half-lives as low as 1 min, which is competitive with the some of best heterogeneous hydrolysis catalysts reported to date.
Mian, Mohammad Rasel,Islamoglu, Timur,Afrin, Unjila,Goswami, Subhadip,Cao, Ran,Kirlikovali, Kent O.,Hall, Morgan G.,Peterson, Gregory W.,Farha, Omar K.
p. 6998 - 7004
(2020/09/02)

Mono- And Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights
Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K4[Sc(H2O)PW11O39]·22H2O·2(CH3COOK) (1) and di-Sc-substituted Na7[Sc2(CH3COO)2PW10O38]·10H2O·2CH3COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by 31P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97percent) is much better than that of 1 (conversion: 28percent). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.
Chi, Yingnan,Dong, Jing,Hu, Changwen,Lin, Zhengguo,Zhang, Di,Zhang, Wenqi,Zhen, Ni
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(2020/07/21)

Synthesis, Characterization, and Phosphoesterase Activity of a Series of 4f- And 4d-Sandwich-Type Germanotungstates [(n-C4H9)4N]l/ mH2[(M(H2O)3)(γ-GeW10O35)2] (M = CeIII, NdIII, GdIII, ErIII, l = 7; ZrIV
We report on a family of five new 4f- and 4d-doped sandwich-type germanotungstates with the general formula [(n-C4H9)4N]l/mH2[(M(H2O)3)(γ-GeW10O35)2]·3(CH3)2CO [M(H2O)3(GeW10)2] (M = CeIII, NdIII, GdIII, ErIII, l = 7; ZrIV, m = 6), which have been synthes
?ip?i?-Paljetak, Hana,Al-Sayed, Emir,Roller, Alexander,Rompel, Annette,Tanuhadi, Elias,Verbanac, Donatella
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p. 14078 - 14084
(2020/10/09)

Photolysis of chlorpyrifos-methyl, chlorpyrifos-methyl oxon, and 3,5,6-trichloro-2-pyridinol
The photodegradation of chlorpyrifos-methyl (1), and two of its photodegradation products, chlorpyrifos-methyl oxon (2), and 3,5,6-trichloro-2-pyridinol (3) was studied using low pressure Hg lamps irradiating at 254?nm either in pure acetonitrile (ACN) or in 10% ACN/H2O. Experiments conducted in pure ACN allowed us to identify the photoproducts in the photolysis of 1, 2, and 3 both, in air saturated samples and in the absence of oxygen as analyzed by gas chromatography–mass spectrometry (GC-MS), high resolution mass spectrometry (HRMS), and phosphorus-31 nuclear magnetic resonance (31P NMR). Since 2 and 3 are products in the photodegradation of 1, their degradations in 10% ACN/H2O were independently measured, and it was determined that 1 and 2 degrade at comparable rates. Instead, 3 does not interfere in the measurement since it degrades much faster, and their products do not absorb in the region of 1. Our results indicate that short wave photolysis could become a plausible detoxification mechanism.
Lobatto, Virginia L.,Argüello, Gustavo A.,Buján, Elba I.
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(2019/04/08)

A Redox Strategy for Light-Driven, Out-of-Equilibrium Isomerizations and Application to Catalytic C-C Bond Cleavage Reactions
We report a general protocol for the light-driven isomerization of cyclic aliphatic alcohols to linear carbonyl compounds. These reactions proceed via proton-coupled electron-transfer activation of alcohol O-H bonds followed by subsequent C-C β-scission of the resulting alkoxy radical intermediates. In many cases, these redox-neutral isomerizations proceed in opposition to a significant energetic gradient, yielding products that are less thermodynamically stable than the starting materials. A mechanism is presented to rationalize this out-of-equilibrium behavior that may serve as a model for the design of other contrathermodynamic transformations driven by excited-state redox events.
Ota, Eisuke,Wang, Huaiju,Frye, Nils Lennart,Knowles, Robert R.
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p. 1457 - 1462
(2019/01/25)

Reactivity and mechanism of α-nucleophile scaffolds as catalytic organophosphate scavengers
Despite their unique benefits imparted by their structure and reactivity, certain α-nucleophile molecules remain underexplored as chemical inactivators for the topical decontamination of reactive organophosphates (OPs). Here, we present a library of thirty α-nucleophile scaffolds, each designed with either a pyridinium aldoxime (PAM) or hydroxamic acid (HA) α-nucleophile core tethered to a polar or charged scaffold for optimized physicochemical properties and reactivity. These library compounds were screened for their abilities to catalyze the hydrolysis of a model OP, paraoxon (POX), in kinetic assays. These screening experiments led to the identification of multiple lead compounds with the ability to inactivate POX two- to four-times more rapidly than Dekon 139 - the active ingredient currently used for skin decontamination of OPs. Our mechanistic studies, performed under variable pH and temperature conditions suggested that the differences in the reactivity and activation energy of these compounds are fundamentally attributable to the core nucleophilicity and pKa. Following their screening and mechanistic studies, select lead compounds were further evaluated and demonstrated greater efficacy than Dekon 139 in the topical decontamination of POX in an ex vivo porcine skin model. In addition to OP reactivity, several compounds in the PAM class displayed a dual mode of activity, as they retained the ability to reactivate POX-inhibited acetylcholine esterase (AChE). In summary, this report describes a rationale for the hydrophilic scaffold design of α-nucleophiles, and it offers advanced insights into their chemical reactivity, mechanism, and practical utility as OP decontaminants.
Wong, Pamela T.,Bhattacharjee, Somnath,Cannon, Jayme,Tang, Shengzhuang,Yang, Kelly,Bowden, Sierra,Varnau, Victoria,O'Konek, Jessica J.,Choi, Seok Ki
p. 3951 - 3963
(2019/04/30)

Multiple functional groups in UiO-66 improve chemical warfare agent simulant degradation
A library of 26 mixed ligand UiO-66 analogs was synthesized, characterized, and screened for catalytic degradation of the chemical warfare agent (CWA) simulant dimethyl 4-nitrophenylphosphate (DMNP). The MOFs were screened and compared to physical mixtures of the same single component MOFs. Several of the MOFs display higher catalytic activity than the parent UiO-66 and other single ligand UiO-66 analogues.
Kalaj, Mark,Palomba, Joseph M.,Bentz, Kyle C.,Cohen, Seth M.
p. 5367 - 5370
(2019/05/10)

Ligand-Directed Reticular Synthesis of Catalytically Active Missing Zirconium-Based Metal-Organic Frameworks
Zirconium-based metal-organic frameworks (Zr-MOFs) based on edge-transitive nets such as fcu, spn, she, csq, and ftw with diverse potential applications have been widely reported. Zr-MOFs based on the highly connected 6,12-connected alb net, however, remain absent on account of synthetic challenges. Herein we report the ligand-directed reticular syntheses and isoreticular expansion of a series of Zr-MOFs with the edge-transitive alb net from 12-connected hexagonal-prismatic Zr6 nodes and 6-connected trigonal-prismatic linkers, i.e., microporous NU-1600, mesoporous NU-1601, and mesoporous NU-1602. These Zr-MOFs exhibit remarkable activities toward the destruction of a nerve agent (soman) and a nerve agent simulant (DMNP).
Chen, Zhijie,Li, Penghao,Wang, Xingjie,Otake, Ken-Ichi,Zhang, Xuan,Robison, Lee,Atilgan, Ahmet,Islamoglu, Timur,Hall, Morgan G.,Peterson, Gregory W.,Stoddart, J. Fraser,Farha, Omar K.
p. 12229 - 12235
(2019/08/27)

Scalable and Template-Free Aqueous Synthesis of Zirconium-Based Metal-Organic Framework Coating on Textile Fiber
Organophosphonate-based nerve agents, such as VX, Sarin (GB), and Soman (GD), are among the most toxic chemicals to humankind. Recently, we have shown that Zr-based metal-organic frameworks (Zr-MOFs) can effectively catalyze the hydrolysis of these toxic chemicals for diminishing their toxicity. On the other hand, utilizing these materials in powder form is not practical, and developing scalable and economical processes for integrating these materials onto fibers is crucial for protective gear. Herein, we report a scalable, template-free, and aqueous solution-based synthesis strategy for the production of Zr-MOF-coated textiles. Among all MOF/fiber composites reported to date, the MOF-808/polyester fibers exhibit the highest rates of nerve agent hydrolysis. Moreover, such highly porous fiber composites display significantly higher protection time compared to that of its parent fabric for a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). A decreased diffusion rate of toxic chemicals through the MOF layer can provide time needed for the destruction of the harmful species.
Ma, Kaikai,Islamoglu, Timur,Chen, Zhijie,Li, Peng,Wasson, Megan C.,Chen, Yongwei,Wang, Yuanfeng,Peterson, Gregory W.,Xin, John H.,Farha, Omar K.
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p. 15626 - 15633
(2019/10/11)

Investigating the breakdown of the nerve agent simulant methyl paraoxon and chemical warfare agents GB and VX using nitrogen containing bases
A range of nitrogen containing bases was tested for the hydrolysis of a nerve agent simulant, methyl paraoxon (MP), and the chemical warfare agents, GB and VX. The product distribution was found to be highly dependant on the basicity of the base and the quantity of water used for the hydrolysis. This study is important in the design of decontamination technology, which often involve mimics of CWAs.
Wilson, Craig,Cooper, Nicholas J.,Briggs, Michael E.,Cooper, Andrew I.,Adams, Dave J.
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p. 9285 - 9291
(2019/01/03)

An Unusual Two-Step Hydrolysis of Nerve Agents by a Nanozyme
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
p. 4840 - 4845
(2018/09/27)

Green and rapid mechanosynthesis of high-porosity NU- and UiO-type metal-organic frameworks
The use of a dodecanuclear zirconium acetate cluster as a precursor enables the rapid, clean mechanochemical synthesis of high-microporosity metal-organic frameworks NU-901 and UiO-67, with surface areas up to 2250 m2 g-1. Real-time X-ray diffraction monitoring reveals that mechanochemical reactions involving the conventional hexanuclear zirconium methacrylate precursor are hindered by the formation of an inert intermediate, which does not appear when using the dodecanuclear acetate cluster as a reactant.
Fidelli, Athena M.,Karadeniz, Bahar,Howarth, Ashlee J.,Huski?, Igor,Germann, Luzia S.,Halasz, Ivan,Etter, Martin,Moon, Su-Young,Dinnebier, Robert E.,Stilinovi?, Vladimir,Farha, Omar K.,Fri??i?, Tomislav,U?arevi?, Krunoslav
p. 6999 - 7002
(2018/07/05)

Zirconium Metal-Organic Framework UiO-66: Stability in an Aqueous Environment and Its Relevance for Organophosphate Degradation
Zirconium-based metal-organic frameworks were recently investigated as catalysts for degradation of organophosphate toxic compounds, such as pesticides or chemical warfare agents. The most utilized UiO-66 is considered as a stable material for these applications in an aqueous environment. However, the presented results indicate that the properties of UiO-66 are changing considerably in aqueous media under common conditions used for organophosphate degradations, and therefore its catalytic activity is not related to the number of structural defects created during the material synthesis. We delineate the stability of UiO-66 in water of various pHs, the in situ formation of new catalytic sites, and the correlation of these two parameters with the degradation rate of a model organophosphate pollutant, dimethyl-4-nitrophenyl phosphate (methyl-paraoxon). The stability was quantified using high-performance liquid chromatography (HPLC) by measuring the amounts of leached terephthalic acid, the linker of UiO-66, and monocarboxylic acids, the modulators bound at UiO-66 defects. We demonstrate that the HPLC analysis is a more suitable method for metal-organic frameworks stability assessment than commonly used methods, e.g., powder X-ray diffraction, adsorption isotherms, or electron microscopy.
Bu?ek, Daniel,Demel, Jan,Lang, Kamil
supporting information
p. 14290 - 14297
(2018/11/26)

A Flexible Metal-Organic Framework with 4-Connected Zr6 Nodes
Zr-based metal-organic frameworks (MOFs) have been known for their excellent stability; however, due to the high connectivity of the Zr6 nodes, it is challenging to introduce flexibility into Zr-MOFs. Here we present a flexible Zr-MOF named NU-1400 comprising 4-connected Zr6 nodes and tetratopic linkers. It exhibits guest-dependent structural flexibility with up to 48% contraction in the unit cell volume as evidenced by single-crystal X-ray diffraction studies. The expanded or contracted conformations of NU-1400 showed drastically different reactivity toward the hydrolysis of a nerve agent simulant owing to the size-selective effect toward the reactant.
Zhang, Yuanyuan,Zhang, Xuan,Lyu, Jiafei,Otake, Ken-Ichi,Wang, Xingjie,Redfern, Louis R.,Malliakas, Christos D.,Li, Zhanyong,Islamoglu, Timur,Wang, Bo,Farha, Omar K.
supporting information
p. 11179 - 11183
(2018/09/06)

Cerium(IV) vs Zirconium(IV) Based Metal-Organic Frameworks for Detoxification of a Nerve Agent
A study was conducted to demonstrate cerium(IV) vs zirconium(IV) based metal-organic frameworks (MOFs) for detoxification of a nerve agent. The rate of hydrolysis observed using a dehydrated version of NU-1000, where ligated water and hydroxide were removed with thermal treatment, was much faster than that of as-synthesized NU-1000. Experiments of this kind showed that Ce-BDC and UiO-66 had similar densities of defect sites. DRIFTS spectra revealed that the sharp peak at 3674 cm-1 corresponding to the hydroxyl groups on the Zr6 node of UiO-66 was shifted to 3646 cm-1 in Ce-BDC, which suggested weaker O-H bonds in the case of Ce6 node.
Islamoglu, Timur,Atilgan, Ahmet,Moon, Su-Young,Peterson, Gregory W.,Decoste, Jared B.,Hall, Morgan,Hupp, Joseph T.,Farha, Omar K.
p. 2672 - 2675
(2017/04/21)

Microwave-assisted activation and modulator removal in zirconium MOFs for buffer-free CWA hydrolysis
A novel, facile and efficient method was developed for the activation of acetic acid modulated zirconium MOFs. The protocol involves briefly heating the material in water using microwave irradiation. MOF-808, DUT-84 and UiO-66 were all activated in this manner to remove the modulator and organic solvent from the framework post synthesis, with retention of MOF integrity post activation. The degree of activation was characterised by the use of TGA and NMR. The catalytic activity of the activated MOFs and their non-activated counterparts was investigated for chemical warfare agent (CWA) hydrolysis. Upon activation, an increase in the rate of hydrolysis was observed in the degradation of CWA simulant dimethyl 4-nitrophenyl phosphate (DMNP). MOF-808 and DUT-84 were also screened as catalysts for the hydrolysis of the V-series agent VM, with remarkable half-lives obtained for MOF-808 in the absence of any buffers. Currently employed MOF activation procedures involve the use of additional organic solvents post synthesis; we believe this method to be ideally efficacious for the organic desolvation of zirconium MOFs and removing modulator additives.
Kalinovskyy,Cooper,Main,Holder,Blight
p. 15704 - 15709
(2017/12/02)

A visually detectable pH responsive zirconium metal-organic framework
A halochromic Zr6-based metal-organic framework is synthesized using solvent-assisted linker incorporation (SALI) with NU-1000 as a platform and carboxylnaphthofluorescein as a pH sensitive ligand. The functionalized MOF can catalytically detoxify nerve agent simulants in addition to visually detecting the acidic byproduct produced during detoxification.
Moon, Su-Young,Howarth, Ashlee J.,Wang, Timothy,Vermeulen, Nicolaas A.,Hupp, Joseph T.,Farha, Omar K.
supporting information
p. 3438 - 3441
(2016/02/27)

Ultra-Fast Degradation of Chemical Warfare Agents Using MOF–Nanofiber Kebabs
The threat associated with chemical warfare agents (CWAs) motivates the development of new materials to provide enhanced protection with a reduced burden. Metal–organic frame-works (MOFs) have recently been shown as highly effective catalysts for detoxifying CWAs, but challenges still remain for integrating MOFs into functional filter media and/or protective garments. Herein, we report a series of MOF–nanofiber kebab structures for fast degradation of CWAs. We found TiO2coatings deposited via atomic layer deposition (ALD) onto polyamide-6 nanofibers enable the formation of conformal Zr-based MOF thin films including UiO-66, UiO-66-NH2, and UiO-67. Cross-sectional TEM images show that these MOF crystals nucleate and grow directly on and around the nanofibers, with strong attachment to the substrates. These MOF-functionalized nanofibers exhibit excellent reactivity for detoxifying CWAs. The half-lives of a CWA simulant compound and nerve agent soman (GD) are as short as 7.3 min and 2.3 min, respectively. These results therefore provide the earliest report of MOF–nanofiber textile composites capable of ultra-fast degradation of CWAs.
Zhao, Junjie,Lee, Dennis T.,Yaga, Robert W.,Hall, Morgan G.,Barton, Heather F.,Woodward, Ian R.,Oldham, Christopher J.,Walls, Howard J.,Peterson, Gregory W.,Parsons, Gregory N.
supporting information
p. 13224 - 13228
(2016/10/30)

Detoxification of Chemical Warfare Agents Using a Zr6-Based Metal–Organic Framework/Polymer Mixture
Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium-based metal–organic frameworks (Zr6-MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant
Moon, Su-Young,Proussaloglou, Emmanuel,Peterson, Gregory W.,DeCoste, Jared B.,Hall, Morgan G.,Howarth, Ashlee J.,Hupp, Joseph T.,Farha, Omar K.
supporting information
p. 14864 - 14868
(2016/10/11)

Synthesis of nanocrystals of Zr-based metal-organic frameworks with csq-net: Significant enhancement in the degradation of a nerve agent simulant
The synthesis of nano-sized particles of NU-1000 (length from 75 nm to 1200 nm) and PCN-222/MOF-545 (length from 350 nm to 900 nm) is reported. The catalytic hydrolysis of methyl paraoxon was investigated as a function of NU-1000 crystallite size and a si
Li, Peng,Klet, Rachel C.,Moon, Su-Young,Wang, Timothy C.,Deria, Pravas,Peters, Aaron W.,Klahr, Benjamin M.,Park, Hea-Jung,Al-Juaid, Salih S.,Hupp, Joseph T.,Farha, Omar K.
supporting information
p. 10925 - 10928
(2015/06/30)

Synthesis, characterization and photocatalytic activity of Ag-TiO2 nanoparticulate film
Ag-TiO2 nanoparticulate film was synthesized by dip coating followed by adsorption and photoreduction in UVA light, characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive analysis of X-rays, glancing angle X-ray diffractometry and UV-Vis absorption spectrophotometry techniques. The data indicated the presence of TiO2 particles of anatase phase of size varying from 5-15 nm, Ag nanoparticles of size varying from 10-20 nm, and also indicated the added visible light activity in Ag-TiO2 nanoparticle films. Photocatalytic degradation of methyl parathion (O,O-dimethyl O-(4-nitrophenyl) phosphorothioate), a well known pesticide in aqueous solution was studied using Ag-TiO2 nanoparticulate film and the data was compared with TiO2 nanoparticulate film. Photocatalytic degradation reactions demonstrated pseudo first order behaviour. Methyl parathion was found to be degraded initially to paraoxon which further was degraded to p-nitrophenol, trimethyl ester of phosphoric acid, trimethyl ester of phosphothioic acid, and finally to phosphate ion. Minute amounts of carbon dioxide and acetaldehyde were also detected. This journal is
Ramacharyulu,Praveen Kumar,Prasad,Srivastava
p. 1309 - 1314
(2015/02/02)

Simple and compelling biomimetic metal-organic framework catalyst for the degradation of nerve agent simulants
Inspired by biology, in which a bimetallic hydroxide-bridged zinc(II)-containing enzyme is utilized to catalytically hydrolyze phosphate ester bonds, the utility of a zirconium(IV)-cluster-containing metal-organic framework as a catalyst for the methanolysis and hydrolysis of phosphate-based nerve agent simulants was examined. The combination of the strong Lewis-acidic ZrIV and bridging hydroxide anions led to ultrafast half-lives for these solvolysis reactions. This is especially remarkable considering that the actual catalyst loading was a mere 0.045 % as a result of the surface-only catalysis observed. Nervous breakdown: UiO-66, a biomimetic metal-organic framework based on a zirconium oxo cluster, is capable of rapidly catalyzing the breakdown of phosphate-based nerve agent simulants. UiO-66 catalyzes both methanolysis and hydrolysis of the nerve agent simulant methyl paraoxon (shown in the graphic, R=CH3) with high catalytic efficiency.
Katz, Michael J.,Mondloch, Joseph E.,Totten, Ryan K.,Park, Jin K.,Nguyen, Sonbinh T.,Farha, Omar K.,Hupp, Joseph T.
p. 497 - 501
(2014/01/23)

Enantiopure water-soluble [Fe4L6] cages: Host-guest chemistry and catalytic activity
Inside information: The new enantiopure cage molecule ΔΔΔ Δ-Fe4L6 (and its enantiomer, ΛΛ ΛΛ-Fe4L6) was prepared by subcomponent self-assembly. It binds a range of organic guests (A, see scheme) in its cavity and distinguishes between the enantiomers of a chiral organic guest. Host ΔΔΔΔ-Fe4L6 is also a catalyst for the hydrolysis (giving B and C) of the neurotoxic organophosphate dichlorvos. Copyright
Bolliger, Jeanne L.,Belenguer, Ana M.,Nitschke, Jonathan R.
supporting information
p. 7958 - 7962
(2013/08/23)

Catalytic solvolytic and hydrolytic degradation of toxic methyl paraoxon with la(catecholate)-functionalized porous organic polymers
Two robust catechol-functionalized porous organic polymers (catPOPs) with different Td-directing nodes were synthesized using a cobalt-catalyzed acetylene trimerization (CCAT) strategy. Postsynthesis metallation was readily carried out with La(
Totten, Ryan K.,Weston, Mitchell H.,Park, Jin Kuen,Farha, Omar K.,Hupp, Joseph T.,Nguyen, Sonbinh T.
p. 1454 - 1459
(2013/07/26)

Molecular engineering of organophosphate hydrolysis activity from a weak promiscuous lactonase template
Rapid evolution of enzymes provides unique molecular insights into the remarkable adaptability of proteins and helps to elucidate the relationship between amino acid sequence, structure, and function. We interrogated the evolution of the phosphotriesteras
Meier, Monika M.,Rajendran, Chitra,Malisi, Christoph,Fox, Nicholas G.,Xu, Chengfu,Schlee, Sandra,Barondeau, David P.,Hoecker, Birte,Sterner, Reinhard,Raushel, Frank M.
supporting information
p. 11670 - 11677
(2013/09/02)

Reactivity of an electrophilic hypervalent iodine trifluoromethylation reagent with hydrogen phosphates - A mechanistic study
The electrophilic trifluoromethylation of hydrogen phosphates with the reagent trifluoromethyl-1,3-dihydro-3,3-dimethyl-1,2-benziodoxole (1) was studied by means of initial rates determined for pseudo first order setups and subsequent Taft analysis of the calculated relative rates. A positive polar sensitivity factor, indicative of a negative charge forming during the rate-determining step, was found for the whole data set.
Santschi, Nico,Geissbühler, Patrik,Togni, Antonio
experimental part
p. 83 - 86
(2012/03/27)

Tailoring the specificity and reactivity of a mechanism-based inactivator of glucocerebrosidase for potential therapeutic applications
Chaperoning an enzyme: Fluorosugar glycosidase inactivators with tunable phosphorus-based leaving groups react quickly with the catalytic nucleophile in β glucocerebrosidase (blue circle; Bn=benzyl). In Western blot analysis, Gaucher patient cells treated with these inactivators show increased intracellular levels of mutant enzyme, presumably because of increased transit from the endoplasmic reticulum (pale blue) to the lysosome (pale pink). Copyright
Rempel, Brian P.,Tropak, Michael B.,Mahuran, Don J.,Withers, Stephen G.
supporting information; experimental part
p. 10381 - 10383
(2011/12/04)

Preparation of a PTE simulacrum based on surface molecular imprinting
Firstly, we synthesized N-methacryloyl-histidine monomer and N-methacryloyl-histidine-Cu2+ complex (MAH-Cu2+). Then the molecular imprinting polymers (MIP) has been prepared by surface grafting on uniform polystyrene (PS) core using
Guo, Yong,Yang, Ying,Guo, Tian Ying
experimental part
p. 493 - 496
(2012/01/19)

Dissociative solvolytic cleavage of methyl (ortho-Carboxymethyl)Aryl phosphate diesters mediated by Yb3+ in methanol gives a 10 12-fold rate acceleration attributable to leaving group assistance
The Yb3+-catalyzed cleavage of a series of eight methyl aryl phosphates (2a-h) where the aryl groups all contain an ortho-methoxycarbonyl group was studied in acidic methanol from 1.34 ≤ spHs ≤ 3.34 at 25 °C. All substrates show saturation binding of the metal ion that is analyzed to provide a conditional binding constant (K)b for a 1:1 substrate/Yb3+ complex and catalytic rate constant (A cat) that varies between about 2 × 10-3 and 50 × 10-3 s-1 overthe range of substrates. Detailed analysis indicates that at very low c oncentration of Yb3+, 3 equiv of substrate are bound, and with increasing [Yb3+], the binding changes to a 1:1 complex which decomposes by a pathway independent of spHs over the range investigated. Control studies show that substrates without the o-methoxycarbonyl group still bind to the Yb 3+ with approximately the same strength as do the o-methoxycarbonyl containing substrates but have no observable reaction when bound. A Jaffe plot of the kcat vs substituent ?-values indicates that, during the catalyzed reactions of 2a-h, the phenoxy-O and C(O)OCH3 groups accommodate negative and positive charge respectively, the p phosphate and p c(o)OMe values being (1.84 ±0.11) and ( 0.85 ±0.14). For all these substrates, the final reaction products are dimethyl phosphate and the Yb3+ complex of the phenoxide. A study of the binding of the parent phenols to Yb3+ indicates that log(Kbind) = (0.84 ± 0.06)sspKa+ (3.4 ± 0.9), r2 = 0.9664 for phenols containing the o-methoxycarbonyl group; for those lacking that substituent log(Kb ind) = (0.96 ± 0.04)s spKa- (1.73 ± 0.4), (r2 = 0.99). For the catalyzed reacti on the βlg = -0.48, while the βeq = -0.95, leading to a Leffler parameter of α = 0.51. A mechanism is presented for the catalyzed reaction which is highly dissociative, having a transition state where the Yb3+ translocates during the cleavage reaction to assist the leaving group's departure with weak nucleophilic assistance by the solvent methanol. A comparison of the catalyzed rate of reaction with a computed rate of reaction attributable to solvent alone indicates that Yb3+ provides leaving group assistance on the order of 1012-fold, stabilizing the transition state for cleavage by some 16 kcal/mol.
Edwards, David R.,Neverov, Alexei A.,Brown, R. Stan
supporting information; experimental part
p. 368 - 377
(2009/06/28)

A simple DNase model system comprising a dinuclear Zn(II) complex in methanol accelerates the cleavage of a series of methyl aryl phosphate diesters by 1011-1013
The di-Zn(II) complex of 1,3-bis[N1,N′1-(1,5,9- triazacyclododecyl)]propane with an associated methoxide (3:Zn(II) 2:-OCH3) was prepared and its catalysis of the methanolysis of a series of fourteen methyl aryl phosphate diesters (6) was studied at sspH 9.8 in methanol at 25.0 ± 0.1°C. Plots of kobs vs [3:Zn(II)2: -OCH3]free for all members of 6 show saturation behavior from which KM and kcatmax were determined. The second order rate constants for the catalyzed reactions (k catmax/KM) for each substrate are larger than the corresponding methoxide catalyzed reaction (k2-OMe) by 1.4 × 108 to 3 × 109-fold. The values of kcatmax for all members of 6 are between 4 × 10 11 and 3 × 1013 times larger than the solution reaction at sspH 9.8, with the largest accelerations being given for substrates where the departing aryloxy unit contains ortho-NO 2 or C(=O)OCH3 groups. Based on the linear Bronsted plots of kcatmax vs sspK aof the phenol, βIg values of -0.57 and -0.34 are determined respectively for the catalyzed methanolysis of regular substrates that do not contain the ortho-NO2 or C(=O)OCH3 groups, and those substrates that do. The data are consistent with a two step mechanism for the catalyzed reaction with rate limiting formation of a catalyst-coordinated phosphorane intermediate, followed by fast loss of the aryloxy leaving group. A detailed energetics calculation indicates that the catalyst binds the transition state comprising [CH3O -:6]?, giving a hypothetical [3:Zn(II) 2:CH3O-:6]? complex, by -21.4 to -24.5 kcal/mol, with the strongest binding being for those substrates having the ortho-NO2 or C(=O)OCH3 groups.
Neverov, Alexei A.,Liu, C. Tony,Bunn, Shannon E.,Edwards, David,White, Christopher J.,Melnychuk, Stephanie A.,Brown, R. Stan
p. 6639 - 6649
(2008/12/23)

OpdA, a bacterial organophosphorus hydrolase, prevents lethality in rats after poisoning with highly toxic organophosphorus pesticides
Organophosphorus (OP) pesticides poison more than 3,000,000 people every year in the developing world, mostly through intentional self-poisoning. Advances in medical therapy for OP poisoning have lagged, and current treatment is not highly effective with mortality of up to 40% in even the most advanced Western medical facilities. Administration of a broadly active bacterial OP hydrolase to patients in order to hydrolyze OPs in circulation might allow current therapies to be more effective. The objective of this work was to evaluate the efficacy of a new recombinant bacterial OP hydrolase (OpdA), cloned from Agrobacterium radiobacter, in rat models of two chemically distinct but highly toxic and rapidly acting OP pesticides: dichlorvos and parathion. Without OpdA treatment, median time to death in rats poisoned with 3× LD50 of dichlorvos or parathion was 6 min and 25.5 min, respectively. Administration of a single dose of OpdA immediately after dichlorvos resulted in 100% survival at 24 h, with no additional antidotal therapy. After parathion poisoning, OpdA alone caused only a delay to death. However, an additional two doses of OpdA resulted in 62.5% survival at 24 h after parathion poisoning. In combination with pralidoxime therapy, a single dose of OpdA increased survival to 75% after parathion poisoning. Our results demonstrate that OpdA is able to improve survival after poisoning by two chemically distinct and highly toxic OP pesticides.
Bird, Steven B.,Sutherland, Tara D.,Gresham, Chip,Oakeshott, John,Scott, Colin,Eddleston, Michael
p. 88 - 92
(2008/09/18)

Development of an alternative process for the manufacture of a key starting material for cefovecin sodium
A process has been developed for the use of trimethylphosphite for the formation of the six-membered 3,6-dihydro-2H-[1,3]-thiazine ring in the cephem architecture by an intramolecular Horner-Emmons-Wadsworth condensation. The process is a suitable alternative to the traditional Wittig process, which uses trimethylphosphine. The process developed is a highly telescoped reaction pathway consisting of at least six known reaction intermediates that was scaled for production use to produce 2.
Norris, Timothy,Nagakura, Isao,Morita, Hiromasa,McLachlan, Grant,Desneves, Joe
p. 742 - 746
(2012/12/29)

Rapid three-step cleavage of RNA and DNA model systems promoted by a dinuclear Cu(II) complex in methanol. Energetic origins of the catalytic efficacy
A dinuclear Cu(II) complex of 1,3-bis-N1-(1,5,9- triazacyclododecyl)propane with an associated methoxide (2-Cu(II) 2:(-OCH3)) was prepared, and its kinetics of reaction with an RNA model (2-hydroxypropyl-p-nitrophenyl phosphate (1, HPNPP)) and two DNA models (methyl p-nitrophenyl phosphate (3) and iso-butyl p-chlorophenyl phosphate (4)) were studied in methanol solution at sspH 7.2 ± 0.2. X-ray diffraction structures of 2-Cu(II)2:(-OH)(H2O)(CF3SO 3-)3:0.5CH3CH2OCH 2CH3 and 2-Cu(II)2:(-OH)((C 6H5CH2O)2PO2 -)(CF3SO3-)2 show the mode of coordination of the bridging -OH and H2O between the two Cu(II) ions in the first complex and bridging -OH and phosphate groups in the second. The kinetic studies with 1 and 3 reveal some common preliminary steps prior to the chemical one of the catalyzed formation of p-nitrophenol. With 3, and also with the far less reactive substrate (4), two relatively fast events are cleanly observed via stopped-flow kinetics. The first of these is interpreted as a binding step which is linearly dependent on [catalyst] while the second is a unimolecular step independent of [catalyst] proposed to be a rearrangement that forms a doubly Cu(II)-coordinated phosphate. The catalysis of the cleavage of 1 and 3 is very strong, the first-order rate constants for formation of p-nitrophenol from the complex being ～0.7 s -1 and 2.4 × 10-3 s-1, respectively. With substrate 3, 2-Cu(II)2:(-OCH3) exhibits Michaelis-Mentin kinetics with a kcat/KM value of 30 M-1 s-1 which is 3.8 × 107-fold greater than the methoxide promoted reaction of 3 (7.9 × 10-7 M -1 s-1). A free energy calculation indicates that the binding of 2-Cu(II)2:(-OCH3) to the transition states for 1 and 3 cleavage stabilizes them by -21 and -24 kcal/mol, respectively, relative to that of the methoxide promoted reactions. The results are compared with a literature example where the cleavage of 1 in water is promoted by a dinuclear Zn(II) catalyst, and the energetic origins of the exalted catalysis of the 2-Cu(II)2 and 2-Zn(II)2 methanol systems are discussed.
Lu, Zhong-Lin,Liu, C. Tony,Neverov, Alexei A.,Brown, R. Stan
p. 11642 - 11652
(2008/03/18)

Reactions of polybromoethanes with four-coordinate phosphorus acid esters
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Gazizov,Karimova,Chernova,Gazizov,Pudovik,Sinyashin
p. 1170 - 1171
(2008/02/08)

Theoretical and experimental study of reactions of esters of P(IV) acids with pentachloroethane
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Gazizov,Zverev,Karimova,Gazizov,Sinyashin
p. 66 - 68
(2007/10/03)

Does phosphoryl protonation occurs in aqueous phosphoesters solutions
Ionisation of trimethylphosphate (TMP), dimethylphosphate (DMP) and diethylphosphate (DEP) is investigated by acidic titration in water by Raman (R), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. The vibrational frequencies of the PO2- ionic form and the neutral form were found in accord with the literature. While increasing further H+ concentration, the PO band disappears in the benefit of new ones. These results, together with deuteration experiments indicate the presence of a new ionic form positively charged with general formula R1R2R3P(OH)+ or R 1R2P(OH)+2. The pK of this phosphonium entities is lying in the range -2, -4. These results were confirmed by 31P NMR titration. The occurrence of such a phosphonium ion in aqueous solutions might be of crucial importance for biochemical reactions and interactions, owing to the large spread of phosphoryl group in biomolecules and keeping in mind that intracellular compartments are more likely concentrated media with little free water than real aqueous solutions. Furthermore, pK's can be shifted by physical-chemical parameters like dielectric constant and electric field. This may involve at least fractional positive charge apparition that might be important in biochemical regulation by charge-charge and charge-dipole interactions. This finding will gain to be further explored on more complex molecules like phospholipids, nucleic acids and proteins.
Azema,Ladame,Lapeyre,Zwick,Lakhdar-Ghazal
p. 287 - 292
(2007/10/03)

The effects of substrate orientation on the mechanism of a phosphotriesterase
While the underlying chemistry of enzyme-catalyzed reactions may be almost identical, the actual turnover rates of different substrates can vary significantly. This is seen in the turnover rates for the catalyzed hydrolysis of organophosphates by the bacterial phosphotriesterase OpdA. We investigate the variation in turnover rates by examining the hydrolysis of three classes of substrates: phosphotriesters, phosphothionates, and phosphorothiolates. Theoretical calculations were used to analyze the reactivity of these substrates and the energy barriers to their hydrolysis. This information was then compared to information derived from enzyme kinetics and crystallographic studies, providing new insights into the mechanism of this enzyme. We demonstrate that the enzyme catalyzes the hydrolysis of organophosphates through steric constraint of the reactants, and that the equilibrium between productively and unproductively bound substrates makes a significant contribution to the turnover rate of highly reactive substrates. These results highlight the importance of correct orientation of reactants within the active sites of enzymes to enable efficient catalysis. The Royal Society of Chemistry 2005.
Jackson, Colin J.,Liu, Jian-Wei,Coote, Michelle L.,Ollis, David L.
p. 4343 - 4350
(2007/10/03)

Effect of Zn...Zn separation on the hydrolytic activity of model dizinc phosphodiesterases
From the study of highly preorganized model systems, experimental support has been obtained for a possible functional role of the Zn-(H)O...HO(H)-Zn motif in oligozinc hydrolases. The mechanistic relevance of such an array, which may be described as a hydrated form of a pseudo-terminal Zn-bound hydroxide, has recently been supported by DFT calculations on various metallohydrolase active sites. In the present targeted approach, the Zn...Zn distance in two related dizinc complexes has been controlled through the use of multifunctional pyrazolate-based ligand scaffolds, giving either a tightly bridged Zn-O(H)-Zn or a more loosely bridged Zn-(H)O...HO(H)-Zn species in the solid state. Zn-bound water has been found to exhibit comparable acidity irrespective of whether the resulting hydroxide is supported by strong hydrogen-bonding in the O2H3 moiety or is in a bridging position between two zinc ions, indicating that water does not necessarily have to adopt a bridging position in order for its pKa to be sufficiently lowered so as to provide a Zn-bound hydroxide at physiological pH. Comparative reactivity studies on the cleavage of bis(4-nitrophenyl)phosphate (BNPP) mediated by the two dizinc complexes have revealed that the system with the larger Zn...Zn separation is hydrolytically more potent, both in the hydrolysis and the transesterification of BNPP. The extent of active site inhibition by the reaction products has also been found to be governed by the Zn...Zn distance, since phosphate diester coordination in a bridging mode within the clamp of two zinc ions is only favored for Zn...Zn distances well above 4 A. Different binding affinities are rationalized in terms of the structural characteristics of the product-inhibited complexes for the two different ligand scaffolds, with dimethyl phosphate found as a bridging ligand within the bimetallic pocket.
Bauer-Siebenlist, Bernhard,Meyer, Franc,Farkas, Etelka,Vidovic, Denis,Dechert, Sebastian
p. 4349 - 4360
(2007/10/03)

Rate and product studies with dimethyl phosphorochloridate and phosphorochloridothionate under solvolytic conditions
The specific rates of solvolysis of dimethyl phosphorochloridate and of dimethyl phosphorochloridothionate are very well correlated using the extended Grunwald-Winstein equation, with incorporation of the NT solvent nucleophilicity scale and the YCl, solvent ionizing power scale. The sensitivity parameters (l and m) are similar to each other and also similar to previously recorded values for solvolyses of arenesulfonyl chlorides, which were proposed to follow a concerted displacement mechanism. For solvolyses in aqueous ethanol or aqueous methanol the product selectivities (S) are close to unity. For solvolyses in aqueous 2,2,2-trifluoroethanol, the values are too small to accurately measure, showing a very large preference for product formation involving nucleophilic attack by the water component. It is concluded that the chloride and chloridothionate solvolyses, in common with the solvolyses of arenesulfonyl chlorides, follow a concerted displacement mechanism.
Kevill, Dennis N.,Carver, Jeffrey S.
p. 2040 - 2043
(2007/10/03)

Reaction of methyl esters of P(IV) acids with polychlorinated hydrocarbons [4]
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Gazizov,Karimova,Nikolaeva,Pudovik,Gazizov,Khairullin
p. 1295 - 1296
(2007/10/03)

Antitumoral compounds
New spisulosine derivatives of use in treating tumors are of the formula (I) wherein: each X is the same or different, and represents H, OH, OR′, SH, SR′, SOR′, SO2R′, NO2, NH2, NHR′, N(R′)2, CN, halogen, C(=O)H, C(=O)CH3, CO2H, CO2CH3, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaromatic, or two groups X may together form =O; Y is NR1, OR1, PR1, SR1, or halogen, wherein the number of substituents R1 is selected to suit the valency and each R1 is independently selected of H, OH, C(=O)R′, P(=O)R′R″, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, and wherein the dotted line indicates an optional double bond; each Z is the same different, and represents H, OH, OR′, SH, SR′, SOR′, SO2R′, NO2, NH2, NHR′, N(R′)2, NHC(O)R′, CN, halogen, C(=O)H, C(=O)CH3, CO2H, CO2CH3, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaromatic, or two groups Z may together form =O; z is 0 to 25; y is to 0 to 20; R2 is H, C(=O)R′, P(=O)R′R″, S(=O)R′R″, S(=O)2R′, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 Alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl; R3 is H, C(=O)R′, P(=O)R′R″, S(=O)R′R″, S(=O)2R′, substituted or unsubstituted C1-C18 alklyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted aryl; each of the R′, R″ groups is independently selected from the group consisting of H, OH, NO2, NH2, SH, CN, halogen, =O, C(=O)H, C(=O)CH3, CO2H, CO2CH3, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C1-C18 alkoxy, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynl, substituted or unsubstituted aryl; there may be one or more unsaturations in the hydrocarbon backbone defined by the chain (II) and salts thereof; with the exception of a C16-C24 2-amino-3-hydroxyalkane or a C16-C24 2-amino-3-hydroxyalkene.
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(2008/06/13)