Stereochemistry of the oxidation of 1, 2, 3, 5, 6, 7, 8, 8a-octahydro-1-naphthoic acids

Summary It was shown that the oxidation of syn- and anti-1,2,3,5,6,7,8,8a-octahydro-1-naphthoic acids with peroxyacetic acid and with osmium tetraoxide proceed stereospecifically from the side opposite to that of the carboxy group. On the other hand, the oxidation of syn-cis-1,2,3,5,6,7,8,8a-octahydro-1, 2-naphthalenedicarboxylic acid goes in both of the possible sterically different directions with formation of isomeric- and-epoxides.     

Hydroxy-, alkoxy-, aminomethylation of NH-oxaziridines

3,3-Dimethyloxaziridine reacts with chloral and acetaldehyde to give crystalline N-(-hydroxyalkyl)oxaziridines; the reaction with acetaldehyde is reversible. The N-aminomethylation of NH-oxaziridines is not realized, evidently because of the tendency of oxaziridines to iminate nucleophiles. The weakly nucleophilic chloromethylphthalimide and chloromethyl methyl ether give imidomethyl- and methoxymethyloxaziridines. 3,3-Dimethyldiaziridine reacts with excess chloromethyl methyl ether to give the N-monomethoxymethyl derivative. It is shown that -hydroxyalkyloxaziridines and methoxymethyl-substituted oxaziridine and dizaridine do not enter into the aminomethylation of compounds with a labile hydrogen.Communication 54 of the series Asymmetric Nitrogen (see [1] for communication 53); communication 35 of the series Geminal Systems (see [2] for communications 34).Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 24, No. 3, pp. 390–395, March, 1988.     

Plasma Sterilization: A Review of Parameters,Mechanisms, and Limitations

Low-temperature plasma is a promising method for destroying microorganisms, an alternative to conventional methods which have numerous drawbacks. Several plasma-based sterilization technologies are presently under development, but their mechanisms of action are still incompletely understood. Since more than five years, we have investigated the effects of plasma on microorganisms (killing efficacy, and related mechanisms), as well as on the materials being sterilized. This article reports some important observations made during this work, using the commercialized so-called plasma sterilizers and real low-pressure plasma systems. The mechanism of etching (volatilization) of microorganisms by plasma that we have observed, leads us to believe that plasma may constitute a powerful solution to the clinical problems of deactivating also prions and endotoxins. However, plasma effectiveness is influenced by numerous experimental parameters, which we review here. This inherent complexity, and the weak penetrating power of plasma species, that severely limits plasma effectiveness in the presence of organic residues, packaging material, or complex geometries, are the main limitations of plasma sterilization.     

Synthesis of furan analogs of 1, 3, 5-triphenylpyrazoline derivatives

Furan analogs of chalcones are condensed with phenylhydrazine to give a number of ²-pyrazolines hitherto not described in the literature. It is shown that in , -unsaturated ketones, a nitro-group in the nucleus and remote from the carbonyl group makes cyclization to the corresponding ²-pyrazolines more difficult than does one adjacent to the carbonyl.     

The sublimation of argon, krypton, and xenon

In this paper, the sublimation pressure of Ar, Kr, and Xe are obtained as functions of temperature from an exactly integrated form of the Clapeyron equation. No fitting to experimental data of the equilibrium pressure has been necessary. The deviation plots of the sublimation pressure show that the results are satisfactory. The derived enthalpy of sublimation of the three rare gases from T = 0 K up to their respective triple point temperatures are asymmetric, distorted parabolas showing maxima for . The , which is a measure of the cohesion energy of the solid crystals, is easily calculated. A general equation has been obtained for as a function of temperature which also gives the enthalpies of sublimation of neon and radon. The (s + ? + g) triple point coordinates of Rn are reassessed.     

Stereochemistry of feshurin,nevskin, and colladocin

The stereochemistry of feshurin has been suggested on the basis of passage to a substance with a known absolute configuration — conferol. It has been shown that feshurin and nevskin are isomers at the C₆-OH. The configuration of nevskin has been determined. The absolute configuration of colladocin has been established by means of a study of the influence of the orientation of the hydroxy group at C₂ in terpenoid coumarins of the samarcandin series on the chemical shifts of the C₁-CH₂OAr.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 308–311, May–June, 1979.     

Characterization of multilayer-interfaces by X-ray diffraction, TEM, SNMS and AES

Summary Prototypes of Ni-C multilayers (up to 40 periods of typically 5 nm thickness) have been prepared by laser pulse vapour deposition (LPVD) and analyzed by a variety of methods. The work showed near normal X-ray reflectivities of typically 5%; an interface roughness ranging from <1 (determined by image processing of TEM micrographs) to 5 (determined by simulation of X-ray diffraction); a compensation for the roughness component that is caused by the substrate surface and impurity concentrations <1 at.–% in layers and in interfacial regions. X-ray diffraction, transmission electron microscopy and image processing have been successfully used for the investigation of the interfacial regions, whereas depth profiling methods that involve sputtering (SNMS and AES) can not provide resolution below 10 .     

Computational studies of the coordination stereochemistry, bonding, and metal selectivity of mercury

Knowledge of the bonding and selectivity of organic mercury, [H3C-Hg]+ (MeHg+), and inorganic Hg2+ for protein and DNA functional groups is important for understanding the mechanism of heavy metal poisoning. Herein, we elucidate (1) the differences between inorganic Hg2+ and organic MeHg+ in their interactions with different ligands of biological interest, (2) the protein and DNA functional groups that Hg2+ and MeHg+ target in aqueous solution, and (3) the likelihood of "soft" Hg2+ displacing the "borderline" Zn2+ bound to "harder" nitrogen/oxygen-containing side chains such as His and Asp/Glu. The results reveal that, relative to Hg2+, the lower positive charge on MeHg+ results in a longer and weaker bond with a given ligand, in accord with the observed kinetic lability of MeHg+ complexes. They also indicate that negatively charged or polar amino acid side chains containing S-/O-/S/N donors could coordinate to both organic MeHg+ and inorganic Hg2+. In addition, Gua and Cyt could also coordinate to MeHg+ and disrupt Gua...Cyt base pairing. A key novel finding is that Hg2+ is a far better electron acceptor than Zn2+, and can thus accept more negative charge from the Zn ligands than the native Zn2+, thus enhancing Hg-ligand interactions and enabling Hg2+ to displace the native cofactor from zinc essential enzymes and "structural" Zn proteins. The results herein support several possible mechanisms for Hg poisoning. Ways that mercury poisoning could be prevented in cells are discussed.     

Structure of the product of the reaction of elemental phosphorus,propylene oxide,phenol, and triethylamine

The composition and structure of an oligomer has been studied, formed in the reaction of elemental phosphorus (P₄) with propylene oxide, phenol, and triethylamine in the ratio 150.81. It has been found by using mass spectrometry, IR and³¹P NMR spectrometry, chromatography and ebulliometry that the oligomer represents a chain consisting of fragments of isopropylphosphonous acid. Products of side reactions have been identified.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2244–2247, October, 1989.     

Preparation, microstructure, and property characterizations of fluorinated polyimide-organosilicate hybrids

Synthesis of organosilicate (orgSiO₂) via sol-gel process utilizing tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS) as precursors was carried out in this work. Various amounts of orgSiO₂ were blended with fluorinated poly(amic acid) (PAA) to form the PAA-orgSiO₂ precursors and the fluorinated polyimide (PI)-orgSiO₂ (i.e., the HR1) thin-film hybrids were prepared via spin coating and curing treatments. The PI-orgSiO₂-AP (i.e., the HR2) hybrids were also prepared by using the PAA-orgSiO₂ precursors containing the amine silane coupling agent, the 3-aminopropyltriethoxysilane (APTEOS). The effects of APTEOS on promoting the crosslinking between organic and inorganic components as well as the network formation were investigated. Fourier-transform infrared spectroscopy (FTIR) showed that the orgSiO₂ particles indeed formed in the hybrids due to the emergence of absorption bands corresponding to SiOSi and OSiO bonds. Nuclear magnetic resonance (NMR) analyses revealed that the Q⁴ units or, the four bridging bond units, dominate the structure of orgSiO₂. Thermal analysis indicated that the implantation of orgSiO₂ in PI matrix may effectively improve the thermal stability of hybrids. Transmission electron microscopy (TEM) revealed the formation of nano-scale orgSiO₂ particles in both hybrids and the sizes of orgSiO₂ are relating to the Si content. In HR1 hybrids, the particles obviously coarsened when Si content was high while, in HR2 hybrids, the addition of APTEOS effectively suppressed the phase separation and the ultrafine orgSiO₂ particles as small as 5 nm could be achieved in the sample with high Si content. Dielectric measurements showed that the lowest values of dielectric constants are 2.40 and 2.20 for HR1 hybrid at intermediate Si content = 0.4 mol and HR2 hybrid with the highest Si content = 0.8 mol, respectively. The suppression of dielectric constants was attributed to the absence of polar SiOH and SiH₂O functional groups as well as the completion of hydrolysis in the hybrids. Formation of silica xerogels in the hybrids should be another cause of dielectric constant decrement, as indicated by the porosity calculation. Experimental results implied that the control of orgSiO₂ size to imply the closed-form silica structure is essential to the low-dielectric constant properties of hybrids. Leakage current density measurement illustrated that no deterioration effect occurs due to the addition of orgSiO₂ nanoparticles in polymeric matrix and satisfactory electrical properties are preserved for the hybrids for advanced low-dielectric applications.     

Sweet and umami taste: natural products, their chemosensory targets, and beyond

Much of our appreciation of food is due to the excitement of the perception of "sweet" and "umami" taste. With a special focus on natural products, this Review gives a summary of compounds that elicit and modulate "sweet" or "umami" taste responses. It will be discussed how the interaction of these molecules with the oral sweet and umami taste receptors stimulates receptor cells to secrete neurotransmitters to induce neural activity that is conveyed to the cerebral cortex to represent sweet and umami taste, respectively. Recent data also show that a sweet taste is metabolically relevant for fuel homeostasis and linked to appetitive ingestive behavior.     

Thin-layer chromatographic analysis of the products of the hydrogenation of anabasine, ammodendrine, and isoammodendrine

Summary It has been shown by TLC on a nonfixed layer of Al_2O3 that the hydrogenation ofl-anabasine forms four stereoisomers and that of N-acetylanabasine three substances, and the conditions for their chromatography and their R _f values have been determined.The ,-bipiperidyl described previously is actually a mixture of two stereoisomers to which, according to their R _f values, saponified dihydroammodendrine and dihydroisoammodendrine correspond.The product of the reduction of ammodendrine is identical in R _f value with one of the four products from dihydroisoammodendrine. Their hydrolysis leads to the formation of the corresponding stereoisomers of ,-bipiperidyl.Donets Institute of Soviet Trade, Zaporozhe Branch. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 727–722, November–December, 1970.     

Polymerization of Cyclic Monomers, 10,

Methyl 2‐(bicyclo[3.1.0]hex‐1‐yl)acrylate ( 1 ) was synthesized from methyl 2‐(cyclopentene‐1‐yl)‐2‐hydroxyacetate by cyclopropanation, followed by oxidation to the corresponding bicyclic 2‐oxoacetate and Wittig olefination with methyltriphenylphosphonium bromide. Initiated with 2,2′‐azoisobutyronitrile at 65 °C in chlorobenzene, the radical homopolymerization of 1 occurred with opening of the cyclopropane ring leading to a polymer with a glass transition temperature of 90 °C. The reactivity of 1 in radical copolymerization was higher than that of methyl methacrylate.

     

Inclusion Complexation of a Seleno-Organic Antioxidant, Ebselen, with Cyclodextrins in Aqueous Solution

The interaction of ebselen, 2-phenyl-1,2-benzisoselenazol-3(2H)-one, a novel neuroprotective agent, with cyclodextrins (CyDs) in aqueous solution was studied by the solubility method and spectroscopic methods. The ability of sulfobutyl ether -CyD (SBE7--CyD, average degree of substitution= 6.2) to solubilize ebselen was greater, and its stability constant (> 2000 M^-1) was significantly higher than those (< 1000 M^-1) of other CyD complexes employed. The stability constant of the complexes rose as hydrophobicity of the substituents of CyDs increased, whereas it was negligibly affected by change in ionic strength of the medium, indicating a significant contribution of hydrophobic interaction in the complexation. SBE7--CyD gave positive and negative CD bands at around 320 and 350 nm, respectively, indicating that the guest is embedded in the asymmetric locus of the CyD cavity. ¹H-NMR spectroscopic studies suggested that the mono-substituted benzene ring of ebselen is preferably included in the cavity of SBE7--CyD. The results indicate that SBE7--CyD is useful as a solubilizing agent for ebselen.     

Synthesis,Conformation, and Metabolism of a Selenium Bilirubin

Summary. A symmetrical C(10)-selena-bilirubin analog, 8,12-bis(2-carboxyethyl)-7,13-dimethyl-2,3,17,18-tetraethyl-10-selenabiladiene-ac-1,19(21H,24H)-dione was synthesized from 8-(2-carboxyethyl)-2,3-diethyl-7-methyl-(10H)-dipyrrin-1-one in one step by reaction with diselenyl dichloride. The selena-rubin exhibited UV-vis and NMR spectroscopic properties similar to those of the parent mesobilirubin, and like bilirubin and mesobilirubin, it adopts an intramolecularly hydrogen-bonded conformation, shaped like a ridge-tile but with a steeper pitch. The longer C–Se bond lengths (2.2Å) and smaller bond angles at C–Se–C (88°), as compared to C–CH₂–C (1.5Å, 106°), lead to an interplanar angle between the two dipyrrinones of only 72°, which is considerably less than that of bilirubin (100°) and close to that (74°) of its 10-thia-rubin analog. Despite the conformational distortion, the sensitivity of Se toward oxidation and the typically weak C–Se bond, the selena-rubin is metabolized in normal rats, like bilirubin, to acyl glucuronides, which are secreted into bile. In mutant (Gunn) rats lacking bilirubin glucuronosyl transferase (UGT1A1), glucuronide or other metabolites of the selena-rubin were not detected in bile, demonstrating the importance of hepatic glucuronidation for its biliary excretion.     

pH-dependence of 31P-NMR spectroscopic parameters of monofluorophosphate, phosphate, hypophosphate, phosphonate, phosphinate and their dimers and trimers

³¹P-NMR chemical shifts and coupling constants of nine inorganic phosphorus compounds composed of different structural units or oxidation numbers P^V, P^IV, P^III, and P^I were measured in the pH-range 3 11. A concise map of NMR data providing the pH-dependence of the chemical shift (-pH map) was set up to be used for identifying phosphorus compounds under varying pH-conditions. Chemical shifts of monofluorophosphate, as well as most phosphorus compounds of oxidation numbers 5 and 4, were greatly dependent on pH, in contrast to the less or negligible pH-dependence of phosphorus compounds of oxidation numbers 1 and 3. Monofluorophosphate gave the parameters: =+1.3±0.2 ppm and ¹J_PF=870±0.2 Hz, that remained unchanged at pH>6, but varied at pH<6. The practical use of the -pH map was shown with a few kinetic experiments in which monofluorophosphate was enzymatically hydrolyzed by alkaline phosphatase (EC3.1.3.1) at pH 7.2 and non-enzymatically at pH 3.     

Synthesis,characterization, thermal,antimicrobial and antioxidant studies of some transition metal dithiocarbamates

Metal dithiocarbamate complexes of Co(II) [1], Cu(II) [2], Mn(II) [3], Cr(III) [4], and Pd(II) [5] have been synthesized using sodium N-ethyl-N-phenyldithiocarbamate (NaL). The complexes were characterized by elemental analyses, FTIR and UV–vis spectroscopic techniques, magnetic moment, molar conductance and thermal analyses (TGA and DSC). The infrared spectra indicated the coordination of dithiocarbamate through the two sulphur atoms in a symmetrical bidentate fashion. The thermal behavior of these complexes showed that the hydrated complexes lost water molecules in the first step, followed by decomposition of the ligand molecules in the final steps. Mass loss considerations at these final decomposition steps indicate conversion of the complexes to sulphides. The antimicrobial potentials of the complexes were evaluated against some selected bacteria strains (Escherichia coli, Pseudomonas aureginosa, Salmonella typhi and Staphylococcus aureus) and fungi organisms (Aspergillus flavus and Fasiparium oxysporium). The compounds showed a broad spectrum of fungicidal and bactericidal activities which exceeds that of the control drugs at a 100 μg/mL concentration. The antioxidant properties of the ligand and its Cu(II) complex were evaluated in vitro using DPPH assay, and the complex was found to exhibit better radical scavenging ability than the free ligand.     

Synthesis, Conformation, and Metabolism of a Selenium Bilirubin

A symmetrical C(10)-selena-bilirubin analog, 8,12-bis(2-carboxyethyl)-7,13-dimethyl-2,3,17,18-tetraethyl-10-selenabiladiene-ac-1,19(21H,24H)-dione was synthesized from 8-(2-carboxyethyl)-2,3-diethyl-7-methyl-(10H)-dipyrrin-1-one in one step by reaction with diselenyl dichloride. The selena-rubin exhibited UV-vis and NMR spectroscopic properties similar to those of the parent mesobilirubin, and like bilirubin and mesobilirubin, it adopts an intramolecularly hydrogen-bonded conformation, shaped like a ridge-tile but with a steeper pitch. The longer C–Se bond lengths (2.2Å) and smaller bond angles at C–Se–C (88°), as compared to C–CH₂–C (1.5Å, 106°), lead to an interplanar angle between the two dipyrrinones of only 72°, which is considerably less than that of bilirubin (100°) and close to that (74°) of its 10-thia-rubin analog. Despite the conformational distortion, the sensitivity of Se toward oxidation and the typically weak C–Se bond, the selena-rubin is metabolized in normal rats, like bilirubin, to acyl glucuronides, which are secreted into bile. In mutant (Gunn) rats lacking bilirubin glucuronosyl transferase (UGT1A1), glucuronide or other metabolites of the selena-rubin were not detected in bile, demonstrating the importance of hepatic glucuronidation for its biliary excretion.     

The proton affinities of styrene,trsns-β-methylstyrene,and indene

We report experimental and theoretical AM1 proton affinities of styrene,-methylstyrenes, and indene. The computed AM1 proton affinities for the species of interest were in good agreement with the experimental values.trans--Methylstyrene was found to have a proton affinity slightly lower than that of styrene. This is an unusual result since methyl substitution in most classes of compounds increases the proton affinity by 2–4 kcal mol^–1. The lower basicity oftrans--methylstyrene compared to styrene is due to the greater stabilizing effect of the methyl group in the neutral species compared to the cation.