Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q86TM3 (cage)
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The essentially stereochemically pure 1-arylethyl phosphorodiamidites 8 and 9 were irradiated by UV light in acetonitrile, benzene, and cyclohexane (Tables 1-4). Reaction via singlet free-radical pairs, formed by carbon-oxygen bond scission (Scheme 1), which are somewhat longer lived than those from the analogous phosphites 5 and 6, is proposed. Tetramethyl 1-phenylethylphosphorodiamidite (8) gives the photo-Arbuzov rearrangement product 10 in 59% +/- 2% GC yield, based on percent 8 consumed (Tables 1 and 4), along with the free radical dimerization product 2,3-diphenylbutane, 12a, in in amounts corresponding to ca. 19% of the potentially formed 1-phenylethyl radicals. Similarly, from 9, the photorearrangement product 11 is generated in 64 +/- 4% yield (Tables 2 and 4) along with a 18 +/- 2% accountability of the 1-naphthylethyl radicals as 12b. The photorearrangement of stereochemically enriched 8 (R/S = 99:1) gives 10 in which an apparent 67 +/- 2% (100y, eq 3, Table 4) of the initial radical pairs [3,14] recombine with retention of configuration at the stereogenic carbon (34 +/- 3% net retention, eq 5). With TEMPO present, 70% (100y, eq 3) of the initial 1-phenylethyl radicals, 14, from 8 combine with radicals 3 in the solvent cage with retained configuration at carbon (40% percent net retention, eq 5). The yield of product 10 is reduced to 54%, and 12a is absent. Similarly, the five-membered ring naphthylethyl analogue, phosphorodiamidite 9 (R/S = 98:2), affords largely (R)-11 with apparent 34 +/- 3% net retention. The degree of stereorandomization observed in these systems is higher than was reported previously for phosphites 5 and 6. The neglect of reconversion of pro-S 14 to pro-R 14 on the results of these studies is addressed. Estimated maximum values (eq 4) of kcomb/krot (2.3) for the proximate radical pairs [3,14] from 8 with TEMPO present appear to be at least 6-fold smaller than those of the analogous phosphite (R)-5 (average kcomb/krot = 13 with TEMPO present). Possible origins for this effect are proposed.
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PMID:Effect of amino substituents on the stereochemical outcome of the photo-Arbuzov rearrangements of 1-arylethyl phosphorodiamidites. 1593

The scope and limitations of the alkylation of [closo-B12(OH)12]2- using a series of fourteen alkyl and aralkyl halides and two p-toluenesulfonic acid esters in the presence of N,N-diisopropylethylamine have been investigated. The dodecaalkoxy-closo-dodecaborate products, [closo-B12(OR)12]2-, and their hypercloso two-electron oxidation products have been explored. The species [closo-B12(OR)12]2- containing 26 cage-bonding electrons may undergo two reversible, sequential, one-electron oxidation processes, producing a 25-electron radical anion and a 24-electron neutral species. Several oxidizing reagents were investigated for the chemical oxidation of [closo-B12(OR)12]2- and [hypercloso-B12(OR)12]- to [hypercloso-B12(OR)12]. Both FeCl3.6H2O and K3Fe(CN)6 in 90/5/5 ethanol/acetonitrile/H2O were found to be the reagents of choice. The reverse reaction leading from the neutral species to the radical anion and subsequently to the dianion was achieved using sodium borohydride in ethanol. A variety of alkoxyl derivatives have been synthesized by heating the reactants for extended periods of time in acetonitrile at the reflux temperature. The use of elevated reaction temperatures attained by employing moderate argon pressure (autoclave) over the reaction mixture led to drastic reductions in reaction times and increased efficiency. X-ray diffraction studies of substituted dodecabenzyl ether derivatives proved that 2(2-) has approximate Ih symmetry while hypercloso-2, -3, -9, -11, -12, and -13 have approximate D3d point group symmetry due to Jahn-Teller distortion from Ih.
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PMID:Synthesis of stable dodecaalkoxy derivatives of hypercloso-B12H12. 1636 78

The aim of this study was to develop an automated sampling method to measure lovastatin in a conscious and freely moving rat. The blood samples were collected by means of the automated blood sampling system DR-II and the faecal samples were collected using a metabolic cage. The concentration of lovastatin was determined by a reversed-phase liquid chromatographic system with a UV absorbance detector. The mobile phase contained acetonitrile and 10 mm NaH2PO4 in the proportions 60:40 (v/v) with a flow-rate of 1 mL/min. The calibration curve was linear in concentration ranges of 0.05-100 and 0.1-100 microg/mL for lovastatin in blood and faecal samples, respectively. Following pharmacokinetic analysis, we identified that the maximum plasma concentration was around 1.18 +/- 0.08 microg/mL at concentration peak time 120 min and almost 78% of loading dose was accumulated in the faeces within 48 h after lovastatin administration (500 mg/kg, p.o.).
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PMID:An automated blood sampling system to measure lovastatin level in plasma and faeces. 1638 44

The synthesis of the three isomeric tris(pyridylmethylamino)cyclotriguaiacylene cavitands is reported, along with the crystal structures of the 2- and 4-pyridyl derivatives. The generality of a previously described [Ag(2){tris(3-pyridylmethylamino)cyclotriguaiacylene}(2)](2+) dimeric capsule motif and the [Ag(4){tris(4-pyridylmethylamino)cyclotriguaiacylene}(4)](4+) tetrahedron with several silver salts was confirmed in the solid state and the corresponding solution species were investigated by NMR spectroscopy. Host-guest interactions in these systems have been probed and these interactions are demonstrated to alter and influence the self-assembly outcome of the reaction. Notably, introduction of larger glutaronitrile guest molecules to the [Ag(4)L(4)](4+) tetrahedron system prevents formation of the tetrahedral structure, resulting instead in the formation of a 4.8(2) coordination network in the solid state. In the absence of templating acetonitrile guests in the [Ag(2)(3)(2)](2+) capsule system, formation of a cage-based one-dimensional coordination polymer is observed.
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PMID:Tris(pyridylmethylamino)cyclotriguaiacylene cavitands: an investigation of the solution and solid-state behaviour of metallo-supramolecular cages and cavitand-based coordination polymers. 1649 98

Acetone-sensitized irradiation of various o-chlorophenyl allyl ethers in polar solvents led to either (dihydro)benzofurans or chromanes. The reaction appeared to involve photoheterolysis of the aryl-Cl bond followed by phenyl cation addition onto the tethered double bond either in 5-exo or 6-endo modes. The adduct cation gave the end products by deprotonation; addition of chloride anion or of the solvent, depending on the structure; and the conditions used. Preference for the 5-exo mode increased in passing from medium polarity (methylene chloride, ethyl acetate) to high polarity solvents (aqueous acetonitrile, methanol, 2,2,2-trifluoroethanol), for which this was often the exclusive path. The same compounds underwent photohomolysis when irradiated in cyclohexane, and radical cyclization was one of the process occurring. Substitution of a methylene group for the ether oxygen atom made 6-endo cyclization by far the main path in a related o-chlorophenylbutene. Again, the selectivity was higher in polar protic solvents. The results are discussed in terms of in cage ion pair versus free phenyl cation reactions.
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PMID:Intramolecular photoarylation of alkenes by phenyl cations. 1650 54

Photolysis (lambda = 254 nm) of 4-allyl-tetrazolones 2a-c was carried out in methanol, 1-propanol, 1-hexanol, acetonitrile, and cyclohexane. The sole primary photochemical process identified was molecular nitrogen elimination, with formation of pyrimidinones 6a-c. Following the primary photocleavage, secondary reactions were observed in acetonitrile and cyclohexane, leading to phenyl-isocyanate (7), aniline (9), and 1-phenylprop-1-enyl-isocyanate (10a). In alcoholic solutions, the primary products, 6a-c, remained photostable even under extended irradiation, making possible the isolation of 3,4-dihydro-pyrimidinones as stable compounds in very high yields. The observed photostability of pyrimidinones 6a-c in alcohols is ascribed to the excited state quenching via reversible proton transfer, facilitated by the solvent cage stabilization due to formation of hydrogen bonds. The viscosity of alcohols is directly related to the cage effects observed. The photocleavage of 4-allyl-tetrazolones leads probably to a caged triplet radical pair. This hypothesis is confirmed by the solvent viscosity effect on the photolysis quantum yields. Additionally, dissolved molecular oxygen sensitizes the formation of pyrimidinones, as should be expected for a triplet intermediate that can only form the product molecule after T-S conversion, which is accelerated by oxygen.
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PMID:Mechanistic investigations into the photochemistry of 4-allyl-tetrazolones in solution: a new approach to the synthesis of 3,4-dihydro-pyrimidinones. 1662 45

We develop a model of electron transfer reactions at conditions of nonergodicity when the time of solvent relaxation crosses the observation time window set up by the reaction rate. Solvent reorganization energy of intramolecular electron transfer in a charge-transfer molecule dissolved in water and acetonitrile is studied by molecular dynamics simulations at varying temperatures. We observe a sharp decrease of the reorganization energy at a temperature identified as the temperature of structural arrest due to cage effect, as discussed by the mode-coupling theory. This temperature also marks the onset of the enhancement of translational diffusion relative to rotational relaxation signaling the breakdown of the Stokes-Einstein relation. The change in the reorganization energy at the transition temperature reflects the dynamical arrest of the slow, collective relaxation of the solvent related to the relaxation of the solvent dipolar polarization. An analytical theory proposed to describe this effect agrees well with both the simulations and experimental Stokes shift data. The theory is applied to the analysis of charge-transfer kinetics in a low-temperature glass former. We show that the reorganization energy is substantially lower than its equilibrium value for the low-temperature portion of the data. The theory predicts the possibility of discontinuous changes in the dependence of the electron transfer rate on the free energy gap when the reaction switches between ergodic and nonergodic regimes.
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PMID:Solvent reorganization of electron transitions in viscous solvents. 1662 17

Rutaecarpine is an alkaloid isolated from the medicinal herb Evodia rutaecarpa. This study was to evaluate the elimination pathway of rutaecarpine in rat feces and urine. Rutaecarpine and its metabolites (3-, 10-, 11- and 12-hydroxyrutaecarpine) in urine were measured after incubation with beta-glucuronidase. After the rutaecarpine was administered (25 and 100 mg/kg) orally to rats, the urine and fecal samples were collected using a metabolic cage for five consecutive days. For determining rutaecarpine, the mobile phase consisted of acetontrile-10 mM NaH(2)PO(4) (60:40, v/v, pH 4.2 adjusted with orthophosphoric acid) with a flow rate of 1 mL/min. The calibration curve was linear in concentrations of 0.05-50 microg/mL in fecal and urine sample. The results indicated that more than 42% of the rutaecarpine was excreted by feces after oral administration (25 and 100 mg/kg), but only a small amount of rutaecarpine was detected in urine at a higher dose of rutaecarpine (100 mg/kg). After incubation with beta-glucuronidase, the hydroxyrutaecarpine in urine was eluted using methanol-acetonitrile-0.04% formic acid (6:30:64, v/v) with a flow rate of 1.2 mL/min. We conclude that the metabolic pathway of rutaecarpine went through phase I hydroxylation and phase II conjugation, and the major metabolite is 10-hydroxyrutaecarpine eliminated from urine of the rat.
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PMID:Elimination of rutaecarpine and its metabolites in rat feces and urine measured by liquid chromatography. 1679 25

Of current interest in our laboratory is the nature of photoinduced processes in the cavities of zeolites completely submerged in polar solvents, or polar-solvated zeolites (PSZ). The present study addresses the nature of electron trapping in PSZ with emphasis on the zeolites NaX and NaY. Free electrons were generated by two-photon, pulsed-laser excitation of either pyrene or naphthalene included in zeolite cavities. Trapped electrons were monitored by diffuse transmittance, transient absorption spectroscopy at visible wavelengths. In anhydrous alcohols, electron trapping by Na(4)(4+) ion clusters was observed in both NaX and NaY. The resulting trapped electrons decayed over the course of tens of milliseconds. No evidence for alcohol-solvated electrons was found. More varied results were observed in solvents containing water. In NaX submerged in CH(3)OH containing 5% or higher water, species having microsecond lifetimes characteristic of solvated electrons were observed. By contrast, a 2 h exposure of NaY to 95/5 CH(3)OH/H(2)O had no effect on electron trapping relative to anhydrous CH(3)OH. The difference between NaX and NaY was explained by how fast water migrates into the sodalite cage. Prolonged exposure to water at room temperature or exposure to water at elevated temperatures was necessary to place water in the sodalite cages of NaY and deactivate Na(4)(4+) as an electron trap. Additional studies in NaY revealed that solvent clusters eventually become lower energy traps than Na(4)(4+) as the water content in methanol increases. In acetonitrile-water mixtures, electron trapping by Na(4)(4+) was eliminated and no equivalent species characteristic of solvated electrons in methanol-water mixtures was observed. This result was explained by the formation of low energy solvated electrons which cannot be observed in the visible region of the spectrum. Measurements of the rate of O(2) quenching in anhydrous solvents revealed rate constants for the quenching of ion cluster trapped electrons that were 2-4 times higher than that for pyrene triplets. In NaX, the rate constant in methanol was 10(4) times smaller than that in cyclohexane, showing greater inhibition of O(2) reactivity in the medium of PSZ. The results of this study point out the conditions under which Na(4)(4+) is active as an electron trap in PSZ and that water must be present in the sodalite cage to produce solvated electrons in the supercage.
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PMID:Electron trapping in polar-solvated zeolites. 1685 43

Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With o-nitropheyl sulfenyl substituted chlorides a stepwise mechanism is observed where through space S...O interactions play an important role stabilizing both the neutral molecules and their reduced forms. Disulfides are generated through a nucleophilic reaction of the two-electron reduction produced anion (arenethiolate) on the parent molecule. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with the gas phase chemical quantum calculations results helped rationalize both the observed change in the ET mechanism and the occurrence of the "sticky dissociative" ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in gas phase. This study shows that despite the low magnitude of in-cage interactions in acetonitrile as compared to in the gas phase, their existence strongly affects the kinetics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents.
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PMID:Radical/Ion pair formation in the electrochemical reduction of arene sulfenyl chlorides. 1713 9


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